Non-Baryonic Dark Matter

a r X i v :h e p -p h /0102327v 1 27 F e

b 2001

CERN–TH/2001-061

Non-Baryonic Dark Matter 1

Leszek Roszkowski 1,2

1

Department of Physics,Lancaster University,Lancaster LA14YB,England

2

TH Division,CERN,CH-1211Geneva 23,Switzerland

Abstract

There exist several well-motivated candidates for non-baryonic cold dark matter,including neutralinos,axions,axinos,gravitinos,Wimpzillas.I review the dark matter properties of the neutralino and the current status of its detection.I also discuss the axino as a new interesting alternative.

CERN–TH/2001-061February 2001

2

Non-Baryonic Dark Matter?

Leszek Roszkowski

Department of Physics,Lancaster University,

Lancaster LA14YB,England

There exist several well-motivated candidates for non-baryonic cold dark matter,including neutralinos,axions, axinos,gravitinos,Wimpzillas.I review the dark matter properties of the neutralino and the current status of its detection.I also discuss the axino as a new interesting alternative.

1.Introduction

The puzzle of the hypothetical dark matter

(DM)in the Universe still remains unresolved[1].

While there may well be more than one type of

DM,arguments from large structures suggest that

a large,and presumably dominant,fraction of

DM in the Universe is made of massive particles

which at the time of entering the epoch of mat-

ter dominance would be already non-relativistic,

or cold.From the particle physics point of view,

cold DM(CDM)could most plausibly be made

of so-called weakly interacting massive particles

(WIMPs).

There exist several interesting WIMP candi-

dates for CDM that are well-motivated by the

underlying particle physics.The neutralino is

considered by many a“front-runner”by be-

ing perhaps the most natural WIMP:it comes

as an unavoidable prediction of supersymmetry

(SUSY).The axion is another well-motivated can-

didate[2].But by no means should one forget

about some other contenders.While some old

picks(sneutrinos and neutrinos with mass in the

GeV range)have now been ruled out as cosmolog-

ically relevant CDM by LEP,axinos(SUSY part-

ners of axions)have recently been revamped[3].

Another well-known candidate is the fermionic

partner of the graviton,the gravitino.Most of

the review will be devoted to the neutralino but I

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mal bath.But in addition there exist also several mechanisms of“non-thermal”production.This

is how CDM axinos,gravitinos can be produced (in addition to“thermal”production),as well as

Wimpzillas[5].

It is obvious that WIMPs do not necessarily have to interact only via weak interactions per

se.WIMPs are generally required to be electri-cally neutral because of stringent observational constraints on the abundance of stable charged

relics.On the other hand,they could in princi-ple carry color charges.(For example,a stable

gluino above130?150GeV[6],or in an experi-mentally allowed window25?35GeV[7],could still be the lightest SUSY particle(LSP)although

its relic abundance would be very small[6].)In a halo they would exist as neutral states by form-ing composites with gluon or quarks.We can see

that generally WIMPs are expected to have sup-pressed e?ective couplings with ordinary matter.

Otherwise,they would dissipate their kinetic en-ergy.

What is the WIMP relic abundance?χh2=

ρχ/ρcrit[8]?Current estimates of the lower bound on the age of the Universe lead to ?TOTAL h2<0.25.Recent results from rich clus-

ters of galaxies and high-redshift supernovae type Ia imply?matter?0.3.The Hubble parameter is now constrained to0.65±0.1.Big Bang nucle-

osynthesis requires?baryon h2～<0.015.Assuming that most matter in the Universe is made of CDM

WIMPs,one therefore obtains

0.1～0.025.

2.Neutralinos

The DM candidate that has attracted perhaps the most wide-spread attention from both the theoretical and experimental communities is the neutralino.It is a neutral Majorana particle,the lightest of the mass eigenstates of the fermionic partners of the gauge and Higgs bosons:the bino, wino and the two neutral higgsinos.If it is the lightest SUSY particle,it is massive and stable,due to assumed R-parity.A perfect candidate for a WIMP!

The neutralino is a well-motivated candidate. It is an inherent element of any phenomenologi-cally relevant SUSY model.Being neutral,it is a natural candidate for the LSP(although one should remember that this is often only an as-sumption);it couples to ordinary matter with a weak-interaction strength(reduced by mixing an-gles)which is within the range of sensitivity of present-day high energy,as well as dark matter, detectors.Finally,as a bonus,it naturally gives ?χh2～1for broad ranges of masses of SUSY particles below a few TeV and for natural ranges of other SUSY parameters.

Much literature has been devoted to the neu-tralino as DM,including a number of comprehen-sive and topical reviews(see,e.g.,Refs.[9,10]). Here I will only summarize the main results and comment on some recent developments and up-dates.

Neutralino properties as DM and ensuing im-plications for SUSY spectra are quite model de-pendent but certain general conclusions can be drawn.First,its cosmological properties are very di?erent depending on a neutralino type.The relic abundance of gaugino-like(mostly bino-like) neutralinos is primarily determined by the(light-est)sfermion exchange in the LSP annihilation into fˉf:?h2∝m4 f/m2χ.In order to have?χ～1, the lightest sfermion cannot be too light(below ～100GeV)nor too heavy(heavier than a few hundred GeV)[11]which is a perfectly natural range of values.

On the other hand,higgsino-likeχ’s are strongly disfavored.Firstly,due to GUT relations among gaugino masses,higgsinos correspond to rather large gluino mass values,above1TeV, which may be considered as unnatural[11].Fur-thermore,higgsino-like neutralinos have been shown to provide very little relic abundance.For mχ>m Z,m W,m t theχpair-annihilation into those respective?nal states(ZZ,W W,tˉt)is very strong.But both below and above those thresholds,there are additional co-annihilation [12]processes of the LSP withχ±1andχ02,which are in this case almost mass-degenerate with the

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LSP.Co-annihilation typically reduces?χh2be-

low any interesting level although it has been re-cently argued that the e?ect of co-annihilation is

not always as strong as previously claimed[13]. Higgsino-like LSPs are thus rather unattractive,

although still possible DM candidates,especially

in the large mass(mχ～>500GeV)regime.One also arrives at the same conclusions in the case

of‘mixed’neutralinos composed of comparable

fractions of gauginos and higgsinos.This is be-cause,even without co-annihilation,in this case the neutralino pair-annihilation is less suppressed and one invariably?nds very small?χthere[11]. Remarkably,just such a cosmologically pre-ferred gaugino type of neutralino typically emerges in a grand-uni?ed scenario with addi-tional assumptions that the mass parameters of all spin-zero particles are equal at the uni?cation scale～1016GeV.What one?nds there is that the lightest bino-like neutralino emerges as essen-tially the only choice for a neutral LSP[14,15].(It is still possible to?nd cases with a higgsino-like LSPs but they are relatively rare.)Furthermore, in order for?χh2not to exceed one or so,other (most notably sfermion)SUSY partner masses have to be typically less than1TeV[14,15]. Thus our phenomenological expectations for low-energy SUSY to be realized roughly below1TeV are nicely consistent with a bino-like neutralino as a dominant component of DM in the Universe. What about the neutralino mass?In princi-ple,it could be considered as a nearly free pa-rameter.It would be constrained from below by the requirement?χh2<1to lie above some 2?3GeV[16]which is a neutralino version of the Lee-Weinberg bound[1].This is because,in this mass range,the neutralino may be viewed as a massive neutrino with somewhat suppressed cou-plings.Much stronger bounds are in many cases provided by LEP.Unfortunately,collider bounds are rather model dependent and are no longer provided for the general SUSY model normally considered in DM studies.Nevertheless,one can reasonably expect that mχis now ruled out below roughly30GeV,except in cases when the sneu-trino is nearly degenerate with the LSP in which case the lower bound may disappear altogether.

A rough upper bound of1TeV follows from the theoretical criterion of naturalness:expecting that no SUSY masses should signi?cantly exceed that value.Again,GUT relations among gaugino masses cause the above constraint to provide a much more stringent(although still only indica-tive)bound of about150?200GeV.Remarkably, in the scenario with additional GUT uni?cation of spin-zero mass parameters,just such a typi-cal upper bound derives from the cosmological constraint?χh2<1.Only in a relatively nar-row range of parameters where the neutralino be-comes nearly mass degenerate with a SUSY part-ner of the tau, τR,the e?ect of the neutralino’s co-annihilation opens up the allowed range of mχup to about600GeV[17].

Summarizing,we can see that,despite the com-plexity of the neutralino parameter space and a large number of neutralino annihilation channels, one can,remarkably,select the gaugino-like neu-tralino in the mass range between roughly30and 150GeV as a natural and attractive DM candi-date.Furthermore,one is able to derive relatively stringent conditions on the mass range of some sfermions,which are consistent with our basic ex-pectations for where SUSY might be realized. 3.Neutralino WIMP Detection

3.1.Predictions

The local halo density of our Milky Way is es-timated at0.3GeV/cm3with a factor of two or so uncertainty[9].For neutralino WIMPs as a dominant component of the halo this translates to about3000LSPs with mass mχ=100GeV per cubic meter.With typical velocities in the range of a few hundred km/s,the resulting?ux of WIMPs is actually quite large

Φ=vρχ/mχ≈109(100GeV/mχ)χ′s/m2/s.(2) A massive experimental WIMP search pro-gramme has been developed during the last few years.Although a variety of techniques have been explored,most of them follow one of the two ba-sic strategies.One can look for DM neutralinos directly,through the halo WIMP elastic scatter-ing o?nuclei,χN→χN,in a detector.Indi-rect searches look for traces of decays of WIMP pair-annihilation products.One promising way

5

is to look for multi-GeV energy neutrinos com-ing from the Sun and/or the core of the Earth.

One can also look for monochromatic photons, positrons or antiprotons produced in WIMP pair-

annihilation in a Galactic halo.I will not discuss these indirect methods here.Perhaps I should only mention about an interesting new way of

looking for WIMPs at the Galactic center[20]. If there is a super-massive black hole there(for which there is now some evidence),it will ac-

crete WIMPs and thus increase their density in the core.They will then be annihilating much

more e?ectively and the resulting?ux of neutri-nos,photons and other products from the cen-ter of the Milky Way may be strongly enhanced,

even up to a factor of105in halo models with central spikes in their pro?les.Such spiked halo models have been obtained in recent N-body sim-

ulations[18].

In the following I would like to make several

comments about direct detection and in particu-lar about an intriguing claim made by the DAMA Collaboration regarding a possible evidence for a

WIMP signal in their data.For a more detailed review,see Ref.[19].First,I will brie?y summa-rize the theoretical aspects and predictions.

In direct searches one of the most sig-ni?cant quantities is the event rate R～σ(χN)(ρχ/mχv)(1/m N)-the product of the

elastic cross sectionσ(χN)of neutralinos from nuclei,their?uxρχ/mχv and the density of tar-

get nuclei with mass m N.

The elastic cross sectionσ(χN)of relic WIMPs scattering o?nuclei in the detector depends on

the individual cross sections of the WIMP scat-tering o?constituent quarks and gluons.For non-relativistic Majorana particles,these can be

divided into two separate types.The coherent part described by an e?ective scalar coupling be-

tween the WIMP and the nucleus is proportional to the number of nucleons in the nucleus.It re-ceives a tree-level contribution from scattering o?

quarks,χq→χq,as described by a Lagrangian L～(χχ)(ˉq q).The incoherent component of the WIMP-nucleus cross section results from an axial

current interaction of a WIMP with constituent quarks,given by L～(χγμγ5χ)(ˉqγμγ5q),and

couples the spin of the WIMP to the total spin of the nucleus.

The di?erential cross section for a WIMP scat-tering o?a nucleus X A Z with mass m A is therefore given by

dσ

d| q|2

+

dσaxial

m A+mχ

v depends on the velocity v of the incident WIMP.The e?ective WIMP-nucleon cross sec-tionsσscalar andσaxial are computed by evalu-ating nucleonic matrix elements of corresponding WIMP-quark and WIMP-gluon interaction oper-ators.

In the scalar part contributions from individual nucleons in the nucleus add coherently and the?-nite size e?ects are accounted for by including the scalar nuclear form factor F(q).(The e?ective in-teraction in general also includes tensor compo-nents but the relevant nucleonic matrix elements can be expanded in the low momentum-transfer limit in terms of the nucleon four-momentum and the quark(gluon)parton distribution func-tion.As a result,the non-relativistic WIMP-nucleon Lagrangian contains only scalar interac-tion terms.)The di?erential cross section for the scalar part then takes the form[9]

dσscalar

πv2

[Zf p+(A?Z)f n]2F2(q),(4) where f p and f n are the e?ective WIMP couplings to protons and neutrons,respectively,and typi-cally f n≈f p.Explicit expressions for the case of the supersymmetric neutralino can be found, e.g.,in the Appendix of Ref.[21].

The e?ective axial WIMP coupling to the nu-cleus depends on the spin content of the nucleon ?q p,n and the overall expectation value of the nu-cleon group spin in the nucleus.For a nucleus with a total angular momentum J we have

dσaxial

πv2

Λ2J(J+1)S(q),(5) withΛ=1

√√

6

are determined by the experimental values of the spin constants?u(p)=?d(n)=0.78,?d(p)=?u(n)=?0.5and?s(p)=?s(n)=?0.16.The e?ective couplings d q depend on the WIMP prop-erties and for the neutralino they can be found, e.g.,in the Appendix of Ref.[21].

In translatingσ(χq)andσ(χg)into the WIMP-nucleon cross section in Eq.(3)several uncertain-ties arise.The nucleonic matrix element coe?-cients for the scalar interaction are not precisely known.Also,the spin content of the nucleon and the expectation values of the proton(neutron) group spin in a particular nucleus are fraught with signi?cant uncertainty and nuclear model depen-dence.These ambiguities have to be considered in numerical calculations.Finally,in order to obtain σ(χN),models of nuclear wave functions must be used.The scalar nuclear form factor re?ects the mass density distribution in the nucleus[9]. The resulting cross section for scalar(or coher-ent)interactions is

σscalar(χN)～G2F

m2χm2N

(m N+mχ)2

(8) which can be shown to be proportional to the spin of the nucleus.(G F is the Fermi constant.) Unfortunately,in supersymmetric models ac-tual calculations produce a rather broad range of values,R～10?5?10events/kg/day.The rates are also very small.The reason why this is so is clear:this is because of smallness ofσ(χN).The elastic cross section is related by crossing sym-metry to the neutralino annihilation cross section σann which is of weak interaction strength and such as to give?χh2～1,and therefore very small.

Such small event rates are clearly an enormous challenge to experimentalists aiming to search for dark matter.One may realistically expect that continuing SUSY searches in high energy accel-erators and improving measurements of?CDM and the Hubble parameter will cause those broad ranges of R to gradually shrink.

The not so good news is that the choices of SUSY parameters for which one?nds the favored

range of the relic abundance,0.1～

R～<10?2events/kg/day or so,typically about an order of magnitude below the reach of today’s detectors.

3.2.Annual Modulation

One promising way of detecting a WIMP is to

look for yearly time variation in the measured en-ergy spectrum.It has been pointed out[22,23] that a halo WIMP signal should show a peri-odic e?ect due to the Sun’s motion through the Galactic halo,combined with the Earth’s rotation around the Sun.The peaks of the e?ect are on the2nd of June and half a year later.

The e?ect,called“annual modulation”,would

provide a convincing halo WIMP signal.Unfortu-nately,in SUSY models the e?ect is usually small,?R～<5%[9,21].With the absolute event rates being already very small,it is going to be a great challenge to detect the e?ect.

Here I would like to make some comments

about possible evidence for a WIMP signal in an-nual modulation that has been claimed by the DAMA Collaboration.Based on the statistics of 14,962kg×day of data collected in a NaI detec-tor over a period from November’96to July’97 (part of run II),the Collaboration has reported [24]a statistically signi?cant e?ect which could be caused by an annual modulation signal due to a WIMP with mass mχand WIMP-proton cross sectionσp given as

mχ=59GeV+22

?14

GeV,(9)

ξ0.3σp=7.0+0.4

?1.7×10?6pb(10) at99.6%CL,whereξ0.3=ρχ/ρ0.3stands for the local WIMP mass densityρχnormalized toρ0.3= 0.3GeV/cm3.(See also Figure6in Ref.[24]for a2σsignal region in the(mχ,ξ0.3σp)plane.)Ac-cording to DAMA,the new analysis is consis-tent with and con?rms the Collaboration’s earlier hint[25]for the presence of the signal based on 4,549kg×day of data.

The claimed e?ect comes from a few lowest bins of the scintillation light energy,just above the software threshold of2keV,and predomi-

7

nantly from the?rst bin(2?3keV).This is indeed what in principle one should expect from the annual modulation e?ect.DAMA appears con?dent about the presence of the e?ect in their data,and claims to have ruled out other possi-ble explanations,like temperature e?ects,radon contamination or nitrogen impurities.Accord-ing to DAMA,the e?ect is caused by single hit events(characteristic of WIMPs unlike neutron or gamma background)with proper modulation of about one year,peak around June,and small enough amplitude of the time dependent part of the signal.

Nevertheless,several experimental questions remain and cast much doubt on the validity of the claim.Here I will quote some which I?nd particularly important to clarify.First,as stated above,the claimed e?ect comes from the low-est one or two energy bins.This is indeed what one should expect from an annual modulation sig-nal.But is the e?ect caused by just one or two energy bins statistically signi?cant?This is es-pecially important in light of the fact that the shape of the di?erential energy spectrum dR/dE in the crucial lowest energy bins as measured by DAMA is very di?erent from the one mea-sured by Gerbier,et al.[26]for the same detec-tor material(NaI).In Ref.[26]the corrected-for-e?ciency dR/dE is about10events/kg/keV/day at3keV,decreasing monotonically down to about 2events/kg/keV/day at6keV.(See Fig.15 in Ref.[26].)In contrast,DAMA’s spectrum shows a dip down to1events/kg/keV/day at2keV,above which it increases to nearly 2events/kg/keV/day at4keV[24,27].It is abso-lutely essential for the controversy of the shape of dR/dE in the lowest energy bins to be resolved. Furthermore,DAMA’s data from the second run (～15000kg×day)shows that the background in the crucial lowest bin([2,3]keV)is only about half or less of that in the next bins[27].One may wonder why this would be the case.Examining more closely the data in the constituent nine NaI crystals,one?nds a rather big spread in the event rates[27].In detector8,in the lowest energy bin one?nds no contribution from the background whatsoever!

Two other groups which have also used NaI have reported[26,28]robust evidence of events of unexpected characteristics and unknown origin. The data of both teams has been analyzed using a pulse shape analysis(PSA).A small but statis-tically signi?cant component was found with the decay time even shorter than the one expected from WIMPs or neutrons.While the popula-tion of those events appears to be too small to explain DAMA’s e?ect,a question remains not only about their origin(contamination?,external e?ect?)but also how they contribute to the en-ergy spectrum in the crucial lowest bins.DAMA claims not to have seen such events.

DAMA has not yet published the data over a full annual cycle.3In particular,no evidence has been published of the signal going down with time.So far,the claimed signal has been based on two periods of data taking.Ref.[25]was based on two relatively short runs,one in winter and one in summer.The second analysis[24]used the data collected between November and July. Much more data has been collected and will soon be published.One should hope that a full and clear analysis of statistical and systematic errors will also be performed.

In Ref.[29]annual modulation was reanalyzed for germanium and NaI.It was concluded that the e?ect would be too small to be seen with current sensitivity.Particularly illuminating is Fig.6.a where DAMA’s data from Ref.[25](run one)was re-plotted along with an expected signal for the modulated part of the spectrum for the central values of the ranges of the WIMP mass and cross section(σp)selected by DAMA.One can hardly see any correlation between the data and the ex-pected signal.

A controversy over DAMA’s alleged signal is of experimental nature.One may therefore hope that it will be de?nitively resolved.It would be of particular importance for another experiment using di?erent detector material to put DAMA’s claim to test.The CDMS cryogenic detection ex-periment using germanium and silicon crystals at Stanford has now reached an adequate sensitivity and has already ruled out about a half of the re-

8

Figure1.The current and some recent limits on the WIMP-proton spin-independent(scalar)cross-section.The legend is as follows:dot:Heidelberg-Moscow Ge[30],solid:DAMA NaI[31],dash:CDMS 19994kg×day Ge with neutron background sub-traction[27].Marked also are the2?σDAMA re-gions:solid closed curve:15,000kg×day,?lled re-gion:20,000kg×day[24].

gion selected by DAMA[27].4Let us hope that DAMA’s claim will be falsi?ed soon.

Figure1shows the current status of WIMP searches in the plane of the WIMP-proton scalar cross-sectionσp versus the WIMP mass.5A claimed DAMA region is also indicated.

It is worth pointing out that the claimed sig-nal region selected by DAMA[24]was too re-strictive as it did not include astrophysical un-certainties.The e?ect is rather sensitive to as-sumptions about a model of the Galactic halo. In the DAMA analysis the peak of the WIMP

9

Figure 2.

A scan of SUSY points in the plane

(m χ,ξ0.3σp )where ξ0.3=ρχ/(0.3GeV /cm 3).The legend:circles:0.10.25(excluded),small points:0.02

and found to a?ect the overall scalar cross-section by a factor of ten or so.

It is worth presenting Figure 3again with an outlook for some expected limits (as claimed by the respective groups)and compare them with predictions of minimal SUSY obtained for very broad ranges of SUSY parameters and neglect-ing nuclear input uncertainties mentioned above.The SUSY region is bounded from above by a somewhat arbitrary requirement ?χh 2>0.025.From below it is limited by a generous bound ?χh 2<1.The SUSY points falling into the cur-rently expected range 0.1～

～<0.15(not indicated in the plane)form a sub-region reach-ing up to roughly a few times 10?6pb.

It is clear that today’s experiments are now only reaching the sensitivity required to begin

Ge [30],solid:DAMA NaI [31],upper dash:CDMS 19994kg ×day Ge with neutron background subtrac-tion [27].Marked also are the 2?σDAMA regions:solid:15,000kg ×day,?lled:20,000kg ×day [24].Future reach of some experiments (as claimed by the respective groups):lower dash:CDMS at Soudan,lower dot:CRESST.Some other experi-ments (e.g.,Edelweiss,UKDMC-Xe,GENIUS)ex-pect to reach roughly similar sensitivities.(Source:https://www.wendangku.net/doc/752523516.html,/limitplots/).

testing predictions coming from SUSY.What I ?nd promising is that several experiments us-ing di?erent detector materials and often di?er-ent methods of [attempts at]distinguishing signal from background will explore a large fraction of the SUSY parameter space within the next few years.Especially reassuring would be an observa-tion of a positive signal in more than type of DM detector,although many experimentalists would probably remark that I am asking for too much.

10

Time will tell.

4.Axinos

Axinos are a natural prediction of the Peccei-

Quinn solution to the strong CP-problem and SUSY.The axino is the fermionic partner of the

axion.Similarly to the axion,the axino couples

to ordinary matter with a very tiny coupling pro-portional to1/f a where109?1010GeV～

It is plausible to consider the axino as the LSP

since its mass is basically a free parameter which can only be determined in speci?c models.As we have seen above,the neutralino has been accepted in the literature as a“canonical”candidate for the LSP and dark matter.But with current LEP bounds between about30and60GeV(depend-ing on a SUSY model),it becomes increasingly plausible that there may well be another SUSY particle which will be lighter than the neutralino, and therefore a candidate for the LSP and dark matter.

Primordial axinos decouple from the thermal soup very early,around T?f a,similarly to the axions.The early study of Ragagopal,et al.[38] concluded that,in order to satisfy?h2<1,the primordial axinos had to be light(～<2keV),cor-responding to warm dark matter,unless in?ation would be invoked to dilute their abundance.In either case,one did not end up with axino as cold DM.

However,it has recently been shown[3]that

the axino can be a plausible cold dark matter can-didate,and that its relic density can naturally be of order the critical density.The axino can be produced as a non-thermal relic in the decays of heavier SUSY particles.Because its coupling is so much weaker,superparticles?rst cascade de-cay to the next lightest SUSY partner(NLSP) for which the most natural candidate would be the neutralino.The neutralino then freezes out from thermal equilibrium at T f?mχ/20.If it were the LSP,its co-moving number density af-ter freeze-out would remain nearly constant.In the scenario of Covi et al.(CKR)[3],the neu-tralino,after decoupling from the thermal equi-librium,subsequently decays into the axino via,e.g.,the process

χ→ aγ(11) as shown in Fig.1in Ref.[3].This process was already considered early on in Ref.[39](see also

Ref.[38])in the limit of a photino NLSP and only

for both the photino and axino masses assumed to be very low,m γ≤1GeV and m a≤300eV, the former case now excluded by experiment.In

that case,the photino lifetime was typically much larger than1second thus normally causing de-struction of primordial deuterium from Big Bang nucleosynthesis(BBN)by the energetic photon. Avoiding this led to lower bounds on the mass of the photino,as a function of f a,in the MeV range[39].

Because both the NLSP neutralino and the

CKR axino are both massive(GeV mass range), the decay(11)is now typically very fast.In the theoretically most favored case of a nearly pure bino,[11,15]the neutralino lifetime can be writ-ten as

τ?3.3×10?2s f a/(NC aY Y)mχ 3(12)

where the factor NC aY Y is of order one.One can see that it is not di?cult to ensure that the decay takes place well before1second in order for avoid problems with destroying suc-cessful predictions of Big Bang nucleosynthesis. The axino number density is equal to that of the NLSP neutralino.Therefore its relic abundance is? a h2= m a/mχ ?χh2.The axinos are ini-tially relativistic but,by the time of matter dom-inance they become red-shifted by the expansion and become cold DM.

There are other possible production mecha-nisms and cosmological scenarios for massive ax-inos.6Even if the primordial population of axi-nos is in?ated away(which would happen if the reheating temperature T reh?f a),they can be regenerated from thermal background processes at high enough T reh

.

11

5.Conclusions

Looking for the invisible is not easy but is cer-tainly worthwhile.The discovery of dark matter will not only resolve the mystery of its nature but is also likely to provide us with much information about the particle physics beyond the Standard Model.What I?nd most encouraging is that we have a very good chance of fully testing the neu-tralino as a WIMP by the end of the decade.De-tecting other candidates,like the axino,will be the task for the more distant future.

Note Added:

After the Conference both the DAMA and CDMS Collaborations published new re-sults.Based on the combined statistics of 57,986kg×day of data collected in a NaI detec-tor since November’96,the DAMA Collaboration reported[41]a statistically signi?cant(4σCL) e?ect which it interprets as being caused by a WIMP annual modulation signal.

The CDMS experiment using germanium and silicon crystals at Stanford published[42]a new limit on scalar WIMP-proton cross section.The new result is based on the total of10.6kg×day of data collected a current shallow site(17mwe)at Stanford during1999.A powerful event-by-event discrimination method allows CDMS to reach a sensitivity matching that of DAMA with only less than0.2%of DAMA’s statistics.

The new90%CL CDMS limit excludes most of the signal region claimed by DAMA.In par-ticular,it fully rules out the previous2σregion based on the combined data of19,511kg×day from runs I and II[24]and the new3σregion at more than84%CL.

An updated compilation of these and other data can be found on the Web: https://www.wendangku.net/doc/752523516.html,/limitplots/.) REFERENCES

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感叹句用法讲解

感叹句 感叹句(exclamatorysentence)用来表示说话人喜怒哀乐、惊讶、赞美等强烈感情的句子。用降调，句末用感叹号，句首多用how和what，其余与陈述句结构相同。 1、带有how的感叹句 用来感叹形容词、副词或动词，其结构： （1）How＋形容词＋主语＋谓语! How happy he is!他是多么的幸福啊! How exciting he became when he heard the news!当他听到这个消息时，他是多么的激动！How beautiful the West Lake is!西湖是多么的美丽啊! （2）How＋副词＋主语＋谓语! How hard he is working now!他现在工作得多么的努力呀! How slowly he runs!他跑得多么慢呀! How beautifully you sing!你唱得多么好听啊！ （3）How＋主语＋动词! How her mother worried!她母亲是多么地担心啊! How he enjoys collecting stamps!他是多么的喜欢集邮啊! How the men pumped like crazy!水手们发疯般地抽着水！ （4）How+形容词+a(an)+可数名词单数形式 Miss Langham arm in arm with Mr.Peabody——how astonishing a sight!兰哈姆小姐挽着皮博迪先生的胳膊，看上去真叫人吃惊！ How interesting a book it is!多么有趣的一本书啊！

（5）How+ many, much, few, little+名词+主语＋谓语! How little food they have!他们的食物多么少啊！ How few books she has!他有的书多么少啊！ 2、带有what的感叹句 带有what的感叹句用来感叹名词，被感叹的名词既可以是可数名词（单数形式或复数形式），也可以是不可数名词。 （1）What a/an＋(形容词)＋单数名词＋谓语! What a fine day it is!天气多么好啊! What an interesting story it is!它是多么有趣的一个故事啊! What an honest boy he is!他是一个多么诚实的孩子呀! What a beautiful day it was and how happy I was!天是多么的好，我是多么的高兴啊!（2）What＋(形容词)＋复数名词＋谓语! What funny stories they are!他们是多么可笑的故事啊! What beautiful colours they are!它们的颜色是多么的漂亮啊! What terrible earthquakes they are!多么可怕的地震啊! （3）What＋(形容词)＋不可数名词＋谓语! What great progress he has made!他取得了多么大的进步呀! What terrible weather we met!我们那时遇到了多么可怕的天气啊! What fun it is to have a swim in summer.夏天游泳是多么有趣的是啊！ 3、感叹句的特殊表达法 （1）不定式短语引起的感叹句

高中英语 知识点大全4 admire、affect、afraid的用法

高中英语知识点大全（4）：admire、affect、afraid的用法1、admire admire（= respect / praise）vt.羡慕，钦佩，夸奖 admire sb.（for sth.）佩服某人某事 Visitors to Beijing greatly admire our Palace Museum. 去北京的游人极其羡慕我们的故宫。 I admire him for his wisdom.我佩服他的智慧。别忘了夸奖孩子。 对比：envy（= jealous）vt.嫉妨，羡慕 envy sb.（sth.）嫉妒/羡慕某人某事 We all envy you your good future. 我们都很羡慕你的好运。 2、affect affect（=have an effect on sth.）vt.影响（effect n.影响） This may affect your health. 这或许会影响你的健康。 My throat is always affected by bad weather.我的嗓子总是受恶劣天气的影响。 3、afraid 1)“be afraid of+名词”，意为“害怕”。 2）“be afraid of doing sth”意为“担心，害怕……”。 3）“be afraid for…”意为“为……担心。” 4）“be afraid that…”意为“担心，恐怕”。 5）“be afraid to do ”意为“害怕，担心而不敢做某事”。

6）I’m afraid so/not.恐怕是这样/恐怕不会这样 [应用]完成句子 ①女孩子一般都怕蛇。Girls are usually______ _____snakes. ②他怕把杯子打碎，因而很小心。He was careful because he was afraid______ _____the glass. ③你不为自己的安全担心吗？Are you afraid_______your safety? ④恐怕她会迷路。I am _____ _____she will lose her way. ⑤汤姆把钱丢了，也不敢告诉他母亲。Tom lost the money and was afraid________ ______his mother. Key:①afraid,of ②of,breaking ③for ④afraid,that ⑤to tell

感叹句的用法

教学目标： 1.让学生了解感叹句。 2.感叹句的三种构成方法。 3 掌握由how和what引导的感叹句。 教学重点： 1 掌握有how和what引导的感叹句. 2 能把how和what引导的两种感叹句互换形式。 教学过程： 第一步：导入、复习 1 感叹句：用以表示喜怒哀乐等强烈感情的句子。如： Look ! Great ! 2 感叹句的标志性符号即感叹号“！”。 3 感叹句一般读降调。 How carefull he studies !(读降调) 第二步：呈现、质疑 1 陈述句、疑问句可构成感叹句。如： It sounds great ! Isn't it interesting ! It's a fine day today ! 2 单词或短语均可构成感叹句。如： Help! Look out! Well done! 3 How或what引导的感叹句。如： How clever! What sweet music! 第三步：拓展提升 1 What引导的感叹句。 What a beautiful girl !

What delicious food ! What bad wheather ! 2 How引导的感叹句。 How exciting ! How big a room (it is) ! How many books he has ! How time flies ! 第四步：知识梳理 1 What 引导的感叹句 What+a\an+形容词+可数名词单数（+主谓）！ What a cute dog ! What+形容词+可数名词复数（+主谓）！ What beautfull flowers ! What+形容词+不可数名词！ What+主语+谓语！ What she must have suffered ! 2 How 引导的感叹句 How+形容词或副词(+主谓）！ How wonderfull ! How+形容词+a\an+可数名词（+主谓）！ How big a room it is ! How+many\much\few\little+名词（+主谓）！ How many books he has ! How+主语+谓语！ How time flies ! 第五步：检测、总结 一将"He is a clever boy. ”变为感叹句. 1 How cever he is ! 2 What a clever boy he is ! 二将What a big room it is !变为由How引导的感叹句。

afraid用法详解总结

afraid用法详解总结 今天给大家带来了afraid用法详解，快来一起学习吧，下面就和大家分享，来欣赏一下吧。 afraid用法详解 【基本用法】 1.害怕的，恐惧的： Dont be afraid. 别怕。 She is afraid of dogs. 她怕狗。 She is afraid of snakes. 她怕蛇。 He was afraid of nothing. 他什么也不怕。 She was afraid of waking him. 她担心把他吵醒。 She was afraid to see you again. 她怕再次见到你。 1 was afraid to tell you. 我不敢告诉你。 They were afraid to be seen by others. 他们怕被别人看到。

He is afraid he will die. 他害怕他会死。 I was afraid I might hurt your feelings. 我担心我会伤害你的感情。 She was afraid they would recognize her. 她担心他们会认出她来。 2.担心的： Im afraid that he wont come. 我担心他不会来。 "Is he not coming?" "I am afraid not.(I’m afraid so.)" “他不来吗?”“看来不会(怕是这样)。” I’m afraid l can’t stay. 恐怕我不能待了。 I’m afraid you don’t see my point. 恐怕你没听懂我的意思。 “Are we late?” “I’m afraid so. ” “我们迟到了吗?”“怕是迟到了。” I’m afraid I must ask you to leave the country. 对不起我得让你离开这个国家。 【考点说明】 1. 通常用作表语，不用于名词前作定语。

初中英语感叹词总结

感叹词是用来表示说话时表达的喜怒哀乐等情感的词。它不构成后面句子的一个语法成分，却在意义上与它有关连，后面的句子一般说明这种情绪的性质、原因。感叹词是英语口语中最富于表现力的词语之一，用途甚广。学会它，对于提高英语的交际能力，表达复杂的思想起着举足轻重的作用。英语中的感叹词很多，但目前的语法著作中却很少对它进行归纳总结，致使许多人对含有感叹词的句子理解不透。现将部分感叹词的用法进行小结： 一、Oh 表示惊讶、指责、痛苦、称赞、懊恼等，可译为“哦”、“哎呀”、“噢”“啊”、“呀”等。 1.“Oh，who was that？” Mr. Black asked.“哦，是谁？”布莱克先生问。 2.“Oh，how blind you are！” he cried.“哎呀，你们真瞎！”他大声道。 3.“Oh，oh！” he cried.“My stomach！My head！oh！oh！”“哎呀，哎哟！”他大声道，“我的肚子！我的头！哎哟！哎哟！” 4.Oh，learned judge！Oh，wise young man.噢，博学的法官！噢，聪明的年轻人！

二、Ah表示惊奇、高兴、讨厌、懊悔、藐视、威胁等，可译为“呀、啊”等。 1.Ah，yes，Jeanne married a man with a lot of money.啊，对啦，让娜嫁给了一个很有钱的人。 2.“Ah，what splendid clothes！” thought the Emperor.“啊！多华丽的衣服啊！”皇帝想。 3.Ah，how pitiful！呀，多可惜！ 4. Ah，here is the thing I am after.哎呀，我找的东西在这儿呢。 三、come表示鼓励、不耐烦、引起注意、安慰等，可译为“喂、好吧、说吧、得啦”等。 1.Oh，come，Mathilde.Surely you can tell an old friend.嗨，说吧，玛蒂尔德，你对老朋友说说总是可以的吧。 https://www.wendangku.net/doc/752523516.html,e，we must hurry.喂，我们得赶紧啦！ https://www.wendangku.net/doc/752523516.html,e，come，get him his change.Tod，get him his change.好吧，好吧，托德，快把钱找给他，快把钱找给他。 4. Come，come！What were you really doing behind the bicycle sheds？喂！喂！你还在车棚里磨蹭啥？

Admire用法和常见搭配

Admire用法和常见搭配 China and Japan have mid-autumn festivals, when people admire the moon and in China, enjoy mooncakes. (P2) 中国和日本都有中秋节，这时，人们会赏月。在中国，人们还品尝月饼。 [点拨]admire vt 倾佩，赞赏，羡慕；夸奖；喜欢admiration n倾佩，赞赏，羡慕admire sb for / (doing) sth 因某事而倾佩、羡慕某人 express admiration for sb对某人表示倾佩I admire her for the way she solves the problem.我倾佩她解决问题的方式。 I admire her for her beauty.我羡慕她的美丽。 I admired and respect you more than I can say. I admired him for his success in business. Everybody admires him for his fine sense of humour. [运用]翻译下列句子 1) 我们佩服居里夫人的发现。

_________________________________________ _________________ 2) The school is widely admired for its excellent teaching. _________________________________________ __________________

高考总复习英语知识点大全4：admire、affect、afraid的用法

v1.0 可编辑可修改高中英语知识点大全（4）：admire、affect、afraid的用法 1、admire admire（= respect / praise）vt.羡慕，钦佩，夸奖 admire sb.（for sth.）佩服某人某事 Visitors to Beijing greatly admire our Palace Museum. 去北京的游人极其羡慕我们的故宫。 I admire him for his wisdom.我佩服他的智慧。 对比：envy（= jealous）vt.嫉妨，羡慕 envy sb.（sth.）嫉妒/羡慕某人某事 We all envy you your good future. 我们都很羡慕你的好运。 2、affect affect（=have an effect on sth.）vt.影响（effect n.影响） This may affect your health. 这或许会影响你的健康。 My throat is always affected by bad weather.我的嗓子总是受恶劣天气的影响。 3、afraid 1)“be afraid of+名词”，意为“害怕”。 2）“be afraid of doing sth”意为“担心，害怕……”。 3）“be afraid for…”意为“为……担心。” 4）“be afraid that…”意为“担心，恐怕”。 5）“be afraid to do ”意为“害怕，担心而不敢做某事”。 6）I’m afraid so/not.恐怕是这样/恐怕不会这样 [应用]完成句子 ①女孩子一般都怕蛇。Girls are usually______ _____snakes. ②他怕把杯子打碎，因而很小心。He was careful because he was afraid______ _____the glass. ③你不为自己的安全担心吗Are you afraid_______your safety ④恐怕她会迷路。I am _____ _____she will lose her way. ⑤汤姆把钱丢了，也不敢告诉他母亲。Tom lost the money and was afraid________ ______his mother. Key:①afraid,of ②of,breaking ③for ④afraid,that ⑤to tell - 1 -- 1 -

感叹词

感叹词 感叹词: 感叹词是用来表示说话时表达的喜怒哀乐等情感的词。它不构成后面句子的一个语法成分，却在意义上与它有关连，后面的句子一般说明这种情绪的性质、原因。感叹词的缩写形式：int.,是英文interjection的缩写 感叹词的用途: 感叹词是英语口语中最富于表现力的词语之一，用途甚广。学会它，对于提高英语的交际能力，表达复杂的思想起着举足轻重的作用。英语中的感叹词很多，但目前的语法著作中却很少对它进行归纳总结，致使许多人对含有感叹词的句子理解不透。现将部分感叹词的用法进行小结： 感叹词的用途分类 Oh: 表示惊讶、指责、痛苦、称赞、懊恼等，可译为“哦”、“哎呀”、“噢”“啊”、“呀”等。 1．“Oh，who was that？” Mr. Black asked．“哦，是谁？”布莱克先生问。 2．“Oh，how blind you are！” he cried．“哎呀，你们真瞎！”他大声道。 3．“Oh，oh！” he cried．“My stomach！My head！oh！oh！” “哎呀，哎哟！”他大声道，“我的肚子！我的头！哎哟！哎哟！” 4．Oh，learned judge！Oh，wise young man．噢，博学的法官！噢，聪明的年轻人！ Ah 表示惊奇、高兴、讨厌、懊悔、藐视、威胁等，可译为“呀、啊”等。 1．Ah，yes，Jeanne married a man with a lot of money．啊，对啦，让娜嫁给了一个很有钱的人。 2．“Ah，what splendid clothes！” thought the Emperor．“啊！多华丽的衣服啊！”皇帝想。 3．Ah，how pitiful！呀，多可惜！ 4．Ah，here is the thing I am after．哎呀，我找的东西在这儿呢。 come表示鼓励、不耐烦、引起注意、安慰等，可译为“喂、好吧、说吧、得啦”等。 1．Oh，come，Mathilde．Surely you can tell an old friend． 嗨，说吧，玛蒂尔德，你对老朋友说说总是可以的吧。 2．Come，we must hurry．喂，我们得赶紧啦！ 3．Come，come，get him his change．Tod，get him his change． 好吧，好吧，托德，快把钱找给他，快把钱找给他。 4．Come，come！What were you really doing behind the bicycle sheds？ 喂！喂！你还在车棚里磨蹭啥？ dear表示后悔、难过、怜悯、同情、吃惊、盼望等，可译为“哎呀、天哪”等。 1．Dear me！What awful weather！哎呀！多糟的天气！ 2．Oh，dear，dear！Where can Harry be？天哪，天哪，亨利会在哪儿？ 3．Dear，dear！Where have I put my keys？哎呀，我把钥匙放在哪啦？ 4．“Dear me，” he said to himself，“Am I foolish or unfit for my office？” “哎呀！”他心里嘀咕着，“我是愚蠢呢还是不称职？” well表示快慰、让步、期望、讥讽、解释、责备、犹豫等，可译为“好吧、不过、好啦、嗯”等。 1．Well，your father has found him in the garage．好啦，你父亲在车库里找到他了。 2．Are you sure？Well，perhaps you，are right．你能肯定吗？嗯，也许你说得对。 3．Well，you must come to lunch tomorrow．不过，你明天一定要来吃午饭。 4．I handed the note to him and said，“Oh，very well，I apologize．”

十类英语感叹词详解

十类英语感叹词详解 感叹词是用来表示说话时表达的喜怒哀乐等情感的词。它不构成后面句子的一个语法成分，却在意义上与它有关连，后面的句子一般说明这种情绪的性质、原因。感叹词是英语口语中最富于表现力的词语之一，用途甚广。学会它，对于提高英语的交际能力，表达复杂的思想起着举足轻重的作用。 英语中的感叹词很多，但目前的语法著作中却很少对它进行归纳总结，致使许多人对含有感叹词的句子理解不透。现将部分感叹词的用法进行小结： 一、Oh 表示惊讶、指责、痛苦、称赞、懊恼等，可译为“哦”、“哎呀”、 “噢”“啊”、“呀”等。 1. "Oh, who was that?" Mr. Black asked. “哦，是谁？”布莱克先生问。 2. "Oh, how blind you are!" he cried. “哎呀，你们真瞎！”他大声道。 3. "Oh, oh!" he cried. "My stomach! My head! Oh! Oh! “哎呀，哎哟！”他大声道，“我 的肚子！我的头！哎哟！哎哟！” 4. Oh, learned judge! Oh, wise young man. 噢，博学的法官！噢，聪明的年轻人！ 二、Ah表示惊奇、高兴、讨厌、懊悔、藐视、威胁等，可译为“呀、啊” 等。 1. Ah, yes, Jeanne married a man with a lot of money. 啊，对啦，让娜嫁给了一个很有 钱的人。 2. "Ah, what splendid clothes!" thought the Emperor.“啊！多华丽的衣服啊！”皇帝想。 3. Ah, how pitiful! 呀，多可惜！ 4. Ah, here is the thing I am after. 哎呀，我找的东西在这儿呢。 三、come表示鼓励、不耐烦、引起注意、安慰等，可译为“喂、好吧、 说吧、得啦”等。 1. Oh, come, Mathilde. Surely you can tell an old friend. 嗨，说吧，玛蒂尔德，你对老 朋友说说总是可以的吧。 2. Come, we must hurry. 喂，我们得赶紧啦！ 3. Come, come, get him his change. Tod, get him his change. 好吧，好吧，托德，快把

英语主动表被动用法归纳

英语主动表被动用法归纳 一、谓语动词用主动表被动的五种情形 (1)某些连系动词(如look, sound, smell, feel, taste, prove等)要用主动表被动，因为连系动词为不及物动词，它们没有被动语态形式： That dog looks dangerous. 那只狗看起来很危险。 Your idea sounds a good one. 你的想法听起来很好。 My advice proved to be wrong. 我的意见证实是错的。 (2)当open, close, shut, lock, move等用作不及物动词且表示主语的某种属性时，通常用主动形式表示被动意义： The door won’t shut. 这门关不上。 The supermarket doors shut automatically. 超市的门是自动关的。 【注】该用法的不及物动词通常与can’t, won’t 等连用，注意它与用被动语态含义不同：The window won’t shut. 这窗户关不上。(说明主语的属性——窗户有问题了) The window won’t be shut. 这窗户将不用关上。(窗户本身没问题，只是不用关) 有时可能用主动和被动形式均可，只是强调重点稍有不同： Suddenly the door opened. 突然门开了。(不强调动作执行者) The door was suddenly opened. 门突然被打开了。(强调动作执行者) (3)当read, wash, clean, cook, cut, wear, carry等用作不及物动词且表示主语的某种属性时，通常要用主动形式表示被动意义： The cloth washes well. 这种布料好洗。 The book sells quickly. 这书销售得快。 This cheese doesn’t cut easily. It’s too soft. 这乳酪不容易切，太软了。 This shirt will wear very long. 这衬衫可以穿很久。 【注】该用法通常与well, easily, slowly, quickly等副词连用，并且在用于以上意思时通常不宜直接使用被动语态形式。不过在某些特殊情况下也可用被动语态，只是含义稍有不同(用主动形式表示主语的属性，用被动形式表示动作执行者所执行的动作)：The sentences read clearly. 这些句子读起来很清楚。(即这句子没有歧义) The sentences are read clearly. 这些句子被读得很清楚。(指读的人读得好) 另外，以上用法有时也可能用于进行时态： The vegetables are cooking. 蔬菜正在煮着。 Is the book selling well? 这书销售情况如何?

史上最全的 构词法 用法详解

史上最全的构词法用法详解 语言中词的总和构成词汇，但是词汇并不是一堆杂乱无章、互不相关的群体，而是一个严密体系，在这个结构的体系中，词与词之间有着各种各样的联系。英语中的这些联系的规律总结起来就是构词。英语中构词的方法就是构词法。构词法主要有合成法、转化法、派生法和缩略法四种。掌握构词法是迅速扩大词汇量的重要方法之一。 第一节合成法 合成法就是指由两个或两个以上的单词合成的词叫合成词。这种构词方式主要有两种：复合法、结合法。合成法主要是构成合成名词和合成形容词。 复合法构成的复合词，它们各个结合的部分相互间的语法关系是紧密相关的。如blackboard和darkroom都是形容词和名词形成的结构，wr it ing desk是动词名词和名词形式的结构。 结合法形成的词是形态合成词，它的结合是用一个起来连接作用的中缀来把两个或两上以上的词根词素紧紧的连缀在一起。如，用辅音字母－s－来缀全两个词根词素构成的词有：salesman, towns people等。 合成的方式常见的有如下几种： 一、合成名词 1、名词／代词＋名词： woman-doctor, women-doctors, workshop, spaceship, he-goat, coal fire, motorcycle, gas cooker, oil well, power plant, silk worm, gold mine, bottleneck, piano keys, teleph one receiver, television screen, chairman, fireman, motorman, police-officer, postman, pine tree, girl friend, boy friend, goldfish, raindrop, birdcage, breakfast time, flowerbed, tearoom, 2、动词＋名词：blowpipe, flashlight, watchdog, call-girl, searchlight 3、形容词＋名词： blacksmith, blackboard, supermarket, superman, darkroom, blackbird, highchair, hothouse, greenhouse, madman 4、动名词＋名词： reading-room, sitting-room, classroom, schoolroom, dining room, building materials, dancing girl, cleaning women, flying machine, washing machine, working conditions, boilding point, drinking water, swimming pool, drinking cup, typing paper, writing desk, sewing machine, walking stick,

感叹句的用法

【概念】 英语中的感叹句用法 感叹句一般用来表示说话时的喜悦、惊讶等情感。 【句式】 感叹句由what 或how引导。what引导的感叹句中心词为名词，how引导的感叹句中心词为形容词或副词。 What+(a / an)+形容词+名词+主语+谓语动词或系动词！ How +形容词或副词+主语+谓语动词或系动词！如： What a beautiful flower it is! What an interesting story it is! What interesting work it is! How interesting the story is! How hard he works! How nice you are, Helen! 当what感叹句中的名词前有形容词修饰时，该句可改为how感叹句，如： What a beautiful flower it is! = How beautiful the flower is! 【如何将陈述句变为感叹句】 以下列句子为例： a. She is a good teacher. b. The flowers smell sweet. 先找句子的主语和谓语动词或系动词，并将之与其他部分划分开； a. She is | a good teacher. b. The flowers smell | sweet.

若其他部分中心词是名词，则用what引导；若中心词是形容词或副词，则用how 引导。a句的中心词为teacher，b句的中心词为 sweet，为此分别用what, how 引导，然后按照感叹句语序写出句子，即： a. What a good teacher she is! b. How sweet the flowers smell! 又如： a. He did so fast. b. She read a good book yesterday.→ a. He did│so fast. b. She read│a good book yesterday.→ a. How fast he did! b. What a good book she read yesterday! 追问： 如果How引导的感叹句省主语和谓语动词 如何在选择题中判断到底是How还是What？-

英语词汇用法

英语词汇用法 1.a/an/the/a book/an apple/an “s”/an hour/a European/at a loss/ in danger/at risk/go on a diet/for fun/be great fun/have a knowledge of 2.abandon one’s family/abandon one’s plan 3.work to the best of one’s ability/ develop one’s ability of listening/ have the ability to do sth 4.be unable to do anything but wait/ an able man 5.abnormal/normal 6.go aboard/go aboard a ship 7.was about to do sth when…/was on the point doing sth = happened to be doing sth when…/what about =how about sth?/set about doing sth=set out to do sth 8.be above the sea level/sb/be ahead of sb/above all 9.go abroad for futher study 10.in the absence of sb/sth = for lack of sth/ sb/sth be absent from 11.absolute ignorance/absolute power /absolute proof/relative/absolutely/ definitely 12.Black cloth absorbs light/absorb a heavy blow/be absorbed in 13.The idea of happiness is abstract/ the abstract of book 14.abuse one’s eye/abuse one’ son 15.academic degree/an academic interest in politics 16.accept…as…/be acceptable to sb 17.the only access to the village/gain access to the house through the window/have/obtain the access to the Internet/be accessible to my car(by car) 18.by accident = by chance = accidentally = occasionally/ accidental 19.accommodation 20.accompany sb to the school/keep sb company/be with/stay with sb/ accompany the singer on piano 21.accomplish wonders/something/ nothing 22.according to what he said/the fact that he was ill 23.account for = explain(to sb)= bring out = set out/account for 4%/ give sb a vivid account of=report vividly/open a bank account/on account of/on no account=under no circumstances=by no means=in no way/at no time/by no means will I do/accountant 24.accumulate a large fortune 25.accurately/accurate timing/timer/ accuracy 26.accuse sb of doing sth/theft/charge sb with doing sth 27.accustom children to getting up early/get (oneself) accustomed to/ accustom oneself to new surrounding 28.achieve one’s goal/set one’s goal/ achieve nothing without effort/ achievement 29.acid taster/acid rain 30.acknowledge doing sth / one’s mistake/acknowledge one’s letter/ be acknowledge as(to be)/admit 31.acquire = obtain 32.get across/ run across/come across = meet with/3 meters across/shout across (through) the room/across the station 33.an act of kindness/in the act of… /Act. / act the part of sb / act out dialogue/act as/act as if/act for /act on(upon) /take strict action to

小学语文感叹句的用法

小学语文感叹句的用法 在劳动场合，人们为了干得更起劲，常常会喊起劳动号子：“同学们，加油干______!” 在这个感叹句中，句末一个字是“干(gàn)”，它的韵尾是“n”，加上韵母“a”合成“na”(哪)，所以这个感叹句中的语气助词应用“哪”。 在花好月圆的晚上，当你凝望窗外的月亮时，会情不自禁地赞叹：“月亮真圆______!” 此句中末字是“圆(yuán)”，它的韵尾是“n”，加上韵母“a”，合成“na”(哪)，因此，这句话中的语气助词也用“哪”。 小学语文感叹句的用法 当你外出旅游，来到黄山、庐山、九寨沟等风景名胜区时，美景立即映入你的眼帘，此时，你定会由衷赞叹：“这里的风景真美______!” 这个感叹句中末字是“美(měi)”，它的韵尾是“i”，加上韵母“a”，合成“ia”，这里的语气助词应用“呀(ya)”。 同学们，你们都读过《狐狸和乌鸦》这个故事吧!那狐狸诡计多端，用花言巧语骗走了乌鸦嘴里的鲜美嫩肉，多么得意!读后，你肯定会说：“多么狡猾的狐狸______!” 这个感叹句中末字是“狸(lí)”它的韵尾是“i”，加上韵母“a”，合成“ia”，所以这里的语气助词也用“呀(ya)”。 小学语文感叹句的用法 如果感叹句末尾那个字的韵尾和韵母“a”不能相拼，就用语气助词“啊”。

如：“多么可爱的鸟儿________!” 这个感叹句中末字是“儿”，它的韵尾是“r”，和韵母“a”不能相拼，就用语气助词“啊”。 又如：“今天我真高兴______!” 此句中“兴”的韵尾是“ng”，和韵母“a”也不能相拼，所以也用“啊”。 有时，“哪”“呀”“哇”也可通用为“啊”，但朗读时仍要按上述规律确定读音。 小学语文感叹句的用法 当你吃到那香喷喷的大米饭时，你的眼前是否会浮现出农民伯伯在田间耕种、收割时那面朝黄土背朝天的劳动情景呢?你一定会说：“我们应爱惜每一粒米，农民伯伯是多么辛苦______!” 这个感叹句中末字是“苦(kǔ)”，它的韵尾是“u”，加上韵母“a”，合成“ua”，这里的语气助词应用“哇(wa)”。 过新年了，当你高高兴兴地穿上新衣服去给亲戚朋友拜年时，他们看见了，会说：“多么漂亮的衣服______!” 此句中末字“服(fú)”的韵尾是“u”，加上韵母“a”，合成“ua”，所以这里的语气助词也用“哇(wa)”。

英语中常用的感叹词

英语中常用的感叹词 感叹词是用来表示说话时表达的喜怒哀乐等情感的词。它不构成后面句子的一个语法成分，却在意义上与它有关连，后面的句子一般说明这种情绪的性质、原因。感叹词是英语口语中最富于表现力的词语之一，用途甚广。学会它，对于提高英语的交际能力，表达复杂的思想起着举足轻重的作用。英语中的感叹词很多，但目前的语法著作中却很少对它进行归纳总结，致使许多人对含有感叹词的句子理解不透。现将部分感叹词的用法进行小结 一、Oh 表示惊讶、指责、痛苦、称赞、懊恼等，可译为“哦”、“哎呀”、“噢”“啊”、“呀”等。 1. "Oh, who was that?" Mr. Black asked. “哦，是谁？”布莱克先生问。 2. "Oh, how blind you are!" he cried. “哎呀，你们真瞎！”他大声道。 3. "Oh, oh!" he cried. "My stomach! My head! oh! oh! “哎呀，哎哟！”他大声道，“我的肚子！我的头！哎哟！哎哟！” 4.Oh, learned judge! Oh, wise young man. 噢，博学的法官！噢，聪明的年轻人！ 二、Ah表示惊奇、高兴、讨厌、懊悔、藐视、威胁等，可译为“呀、啊”等。 1. Ah, yes, Jeanne married a man with a lot of money. 啊，对啦，让娜嫁给了一个很有钱的人。 2. "Ah, what splendid clothes!" thought the Emperor. “啊！多华丽的衣服啊！”皇帝想。 3. Ah, how pitiful! 呀，多可惜！

as引导的从句用法

1 as引导的从句崔长平河南省遂平中学（463100） 在英语中，as作为一个常见的从句引导词，其用法和意义十分活跃而丰富，若不加以区分，很容易造成混淆。现将其主要用法归纳如下： 1）引导时间状语从句①在as引导的时间状语从句中，谓语动词既可以是延续性的也可以是非延续性的；有时从句的谓语动词也可用进行时形式。②as引导的时间状语从句常可用来强调主、从句中的动作同时发生或伴随发生，常译作“随着……”，“一边……一边……”，“一……就……”等。③在省略句中，as之后经常放置一个名词或名词词组。 I heard the murmur of their voices as I crossed the hall. A look of surprise came into Alison’s eyes as she read the message. Scott became nervous as he saw her face. Just as he was speaking there was a loud explosion. He smiled as he passed. As she sang，the tears ran down her cheeks. We get wiser as we get older. As a young man，he was a store keeper and later a postmaster. 2）引导让步状语从句象although，though，while一样，as也可以用来引导一个让步状语从句，意为“尽管，虽然”， as引导的这种让步状语从句语气比较强，语体正规，经常用于书面语言，但as引导的让步状语从句须倒装。其倒装要求如下：①表语＋as＋主语＋系动词（表语经常是由形容词、分词、或名词充当；名词用作表语时，其前不能加用冠词。） Young as he is，he is equal to the task. Crowded as the restaurant was，they tried to find a table. Child as he was，he knew what was the right thing to do. ②状语﹢as﹢主语﹢谓语动词（这一结构中的谓语动词一般是行为动词，既可以是及物动词（带宾语）也可以是不及物动词。） Hard as he studied，he did not get good marks in the exam. Early as we got there，our teacher was there before us. Much as I admire him as a writer I don’t like him as a man. ③动词＋as ＋主语＋……（在这一结构中，主语后面一般加上情态动词may，might，will，would，can，could等，句首的动词应该保持原形。如果从句中没有情态动词，那么，应在从句的主语之后（根据时态和数的要求）加上助动词do、does或did。在这一结构中，放在句首的动词如果是及物动词，那么，这个动词连同它的宾语一起放到as之前。） Search as they would，they could find nothing in the house. Try as he may，he will fail in the examination. Die as he did，his inspiration lived on. Lose money as I did，I got a lot of experience. 3）引导原因状语从句 as引导原因状语从句时，语气不及because强烈，它接近于since，now that，一般译作“既然，由于”之类的意义，只是“附带说明的理由”，表达一种说话人和听话人“共知的原因”。as引导的原因状语从句一般置于主句之前。 As all the seats were full he stood up. As Davidson had a passion for walking，we started off on foot. As you are sorry，I’ll forgive you. It is very difficult for us to know what to do as we are not his parents.