B--Physics in Hadron Colliders
a r X i v :h e p -p h /9309309v 1 21 S e p 1993Fermilab-Pub-93/256-T
September 21,1993
B–PHYSICS IN HADRON COLLIDERS ?CHRISTOPHER T.HILL Fermi National Accelerator Laboratory P.O.Box 500,Batavia,Illinois,60510The possibility of exploring the systematics of the spectroscopy,strong dynamics,and the weak and rare decay modes of b–quark systems at hadron colliders such as Fermilab,LHC and SSC,is discussed.A copi-ous yield of 1010detected B –mesons is readily accessible in a dedicated Fermilab program,and implies a vast array of accessible decay modes,including second order weak processes and CP –violation,which will be unavailable elsewhere until the commissioning of LHC or SSC.Kinematic and ?avor tagging,utilizing the “daughter pions”from resonances,is ex-pected to play a major role in semileptonic weak decay studies and the search for CP –violation.
?Plenary talk,Workshop on B Physics at Hadron Accelerators ,Snowmass,Colorado,June 25,1993;Invited Lecture,TASI ,Boulder,Colorado,June 18,1993.
1.Introduction
1.1.Generalities
The b–quark o?ers a window on the standard model that is open to experi-mentalists at hadron colliders,where the largest yields of b–quarks occur.With existing facilities,such as CDF,it should be possible to achieve～109observable B–decays within the next few years.This entails evolution of the high resolution vertex detectors,e.g.,CDF’s SVX,including full r-θ-z information,and especially generalized triggers,such as single lepton displaced vertices for semileptonic weak decay studies.1,2With a modest yet dedicated program,perhaps involving a new detector,>1010observed B’s should be achievable at Tevatron to Main Injector luminosities within this decade.Such a program is essential to break the ground for future hadron–based B-physics programs at LHC and SSC.An ultimate hadron collider based program at Fermilab,LHC and SSC can look forward to recording the decays of>1012produced B’s.
The present discussion is intended to be primarily a prospectus for such a pro-gram.We will,however,indulge in some speculations about tagging of?avors and the all–important kinematic reconstruction needed to do semileptonic weak stud-ies.This re?ects recent interest that has arisen in the possibility of“daughter pion”tagging,i.e.,using the pions from the decays of parent resonances to tag the?avor.3 The major advantages of the hadron based B–physics environment are the rela-tively large cross–section for b–quark production and the the“broad–band”nature of the beam.b–quark pairs are produced by(predominantly)gluon fusion4and arbi-trarily massive states are available.Thus,all of the spectroscopy,including B c～
b(u,d)combinations can be produced.More-over,in e+e?machines that operate in the continuum or on the Z–peak the cross–section for b production is many orders of magnitude below that in the hadronic environment.
On the other hand these advantages imply major challenges as well.1,2The copious production at hadron machines implies that a substantial parsing of data must occur quickly on–line,i.e.,a trigger that can keep interesting candidate events must be provided.To date in hadronic colliders the semileptonic decay modes have been largely discarded in favor of the much easierψmodes.A trigger capable of recovering the semileptonic decays is possible,and demonstrating its feasibility is of high priority for a number of reasons(conventional?avor tagging requires it).
Another issue is the extent to which decays involving missing mass,such as the semileptonic decays involving neutrinos,can be fully reconstructed.In e+e?ma-chines that make use of theΥ(4S)the B–mesons are produced with a known energy, the beam energy.In combination with the visible decay momentum,this completely determines the decay kinematics,e.g.,the Q2of the lepton pair is determined even though the neutrino is never seen.In a hadronic mode we observe a B–meson?ight direction and the visible momentum of the decay products,but this yields a two–
fold ambiguity in the B energy.Thus,to make maximal use of a semileptonic decay
sample it is imperative that e?cient techniques evolve for resolving this ambiguity!
One technique would“bludgeon”the semileptonic processes with high statistics by insisting on keeping only those special kinematic con?gurations for which the
ambiguity disappears5.While ine?cient,this technique is guaranteed to work.
However,we will suggest another approach presently that is speculative,but may
ultimately prove to be an e?cient way of fully reconstructing B processes with
relatively high e?ciency.It makes use of the fact that B–mesons will often be produced as decay fragments of a resonance as in B??→B+π.Theπmeson here we will call a“daughter pion,”and it has previously been suggested as a?avor
tagging mechanisim for neutral B–mesons.2The observation of daughterπ–mesons
from resonances is established by ARGUS,E-691and CLEO,and E-687.6However, we suggest here that it can potentially be used to resolve the two–fold kinematic ambiguity in the B–meson4–momentum.We describe this approach in Section2.4 below.It may prove workable in some form as our understanding of B production evolves.
The physics goals of a>1010B–meson program are very rich and diverse.
Heavy quark physics allows us to map out the CKM matrix of the standard model
through the detailed studies of inclusive and exclusive decay modes.It will allow
us to test the standard model beyond the leading order in radiative corrections,
and through rare decay modes and mixing phenomena which are sensitive to m top and V tq,etc.This will lead ultimately to experimental tests of the CKM theory of CP–violation,which is expected to manifest itself in many interesting new channels in the b–system.High statistics studies of the b–system will furthermore enable searches for exotic physics,signals of which might be expected to emerge in heavy quark processes.
We begin?rst with a brief overview of the physics considerations that are rele-
vant to doing heavy quark physics in the hadronic collider environment.
1.2.Prima Facie Considerations of Hadronic B’s
B–physics at hadron colliders is often casually dismissed out–of–hand,preference
given to e+e?production,because the hadronic environment is“too noisy.”It is
important to realize that the“noise,”i.e.,the background of high multiplicity,
mostly low p T pions in a hadronic collision,is largely spread out over a large range of rapidity.The low–mass particle production follows an approximately constant distribution in the pseudo–rapidity:
η=?ln[tan(θ/2)]≈tanh?1(p z/E)(1) Typically at Tevatron energies the number of pions per unit rapidity is given by:
dNπ
n=6charged pions,and6
π0gamma’s emanating from the beam collision spot.
Table I:Indicated yields of usable B–mesons running for a3year,30%duty cycle,
period for:(a)Tevatron at present attainable L=1031cm?2sec?1(b)Main Injector
assuming L=1032cm?2sec?1(twice the design goal;multiply by10if the rapidity
range is|η|≤3and p t>5GeV).(c)ABF–Asymmetric B-factory proposal at L=
1034cm?2sec?1operating on theΥ(4S)(d)LEP at Z0–pole with L=2×1031
cm?2sec?1(see M.Artuso in ref.[2]).
Tevatron(a)ABF(c)
6×1093×108
B s1.6×10108×105
107none
Λb10104×105
p collider,for which we assume √
be of order10%,though these are crude estimates at present,and should actually be measured at the end of run I.
This compares with the idealized luminosity of1034cm?2sec?1in an e+e?storage ring,such as the proposed asymmetric B-factory(ABF)at SLAC or CESR (the present peak luminosity at CESR is2.5×1032).The cross-section for B
2,and the
states of lowest mass will have j2=1
2
,1
a massive particle,or O (2)=U (1)for a massless particle).Remarkably,we see that the little group of a heavy–light meson is enlarged to SU (2)×SU (2),since we can rotate the heavy quark independently of the brown muck.The states for which |j 1?j 2|is an integer are equivalent to representations of O (4)=SU (2)×SU (2).Thus the groundstate is equivalent to a 4-plet under O (4),containing the 0?and the 1?mesons.ub, db, ub, d
b ____sb, sb __ _ _ _ _ _ _ _ _ _ _ __ _ _ _ _ _ _ _ _ _ _ __ _ _ _ _ _ _ _ _ _ _ __ _ _ _ _ _ _ _ _ _ _ __ _ _ _ _ _ _ _ _ _ _ _21+
+B (5374)s B (5420)s B (5834)s B (5846)
s B (5767)B (5755)
B (5324)
B(5278)2+1+__MeV
5000
52005400560058006000
6200**********uc, dc, uc, dc ____1600180020002200240026002800
D (1864)
0D (2460)**2 D (2536)**2D (2420)**1 D (2502)**1_ _ _ _ _ _ _ _ _ __ _ _ _ _ _ _ _ _ _D (2010)
* D (2111)*D (1869)+_ D (1968)s s
sc, sc
__1+12+2+MeV +Figure 1.The low–lying spectra of D and B states from EHQ.8Solid lines are estab-lished,dashed lines are predictions (we omit the broad (0+,1+)p-waves 9).
The masses and decay widths of heavy–light resonances have been estimated recently by Eichten,Hill and Quigg (EHQ)8.The masses of these states seem to be well ?t by using a Buchm¨u ller–Tye potential for a static massive quark with a constituent light quark boundstate.Their decay widths were obtained by rescaling the known strange and charm widths with smearing.The spectra are presented in Fig.(1).There will generally occur a (12)=0++1+parity partner of the groundstate (a p –wave in the constituent quark model)which has a very large ～GeV width and will generally be unobservable.9This state may be viewed as the “chiral partner”of the groundstate;9if we imagine restoring the broken chiral symmetry the groundstate would have to linearly realize the chiral symmetry,thus becoming doubly degenerate (thus,the left–handed iso–doublet is 0+?0?,while the right–handed iso–doublet is 0++0?when the chiral symmetry is restored).
2.2.Daughter Mesons
The resonances can be observed by studying the π’s and K ’s produced in asso-ciation with B –mesons.Some of the π–mesons will be decay relics from processes
like:
p+
pp collisions.We would expect(heavy quark symmetry)that
apart from normalization the charm production distributions can be taken over to B-physics directly.Thus,for tagging purposes an inclusive rate of f～20%of B’s
coming from the B??→B?→B and B??→B chains might be expected.The experience in photoproduction suggests that the e?ciency for?nding the daughter
pion is～50%.We will therefore assume an overall tagging e?ciency of～10%by
daughter mesons is possible.
The production tagging e?ciency is probably sensitive to p T and to angular
cuts(or rapidity cuts).The heavy quark limit ensures that the4–velocity of the
produced B??is approximately equal to the4–velocity of the B i.e.,zero–recoil of the
b–system is a good approximation.In hadronic collisions it is probably reasonable to assume that the B??system at low p T is produced in an unpolarized initial state and,thus,the distribution of decay pions in the process B??→B+πis spherical in the B??rest frame.The(unit normalized)polar distribution of pions relative to the B?ight direction is then obtained by boosting the spherical distribution: dN
4π γ(1?β2ω2?((β4?2β2)ω2+β2)cos2θ)+2Aβωcosθ
1?m2π/(?M)2≈1.04.In the massless pion limit,ω=1and this reduces to dN/d?=1/[4πγ2(1?βcosθ)2]valid to order1
γβ=
1
γ2?1(6)
Forγ≈2we see thatθ50%～30o,and this de?nes a cone of small solid angle of 0.07×4πsteradians.The aligned daughter pions,coming from the primary vertex, are also expected be more energetic than typical minimum bias pions.Thus,the conical cut on pions withθ<θ50%should lead to a signi?cant gain in signal to background for low–p T(at high p T the B–meson is enveloped in a jet with higher
πmultiplicity within small conical angle).We do not consider the more general
possibility of rapidity correlations here.3
2.3.Semileptonic Weak Decays involving V cb
High statistics measurements of exclusive semileptonic branching ratios such as
B→l+ν+(D??,D?,D),etc.,are possible at the level of～109decays.These are
important processes for establishing the overall normalization of weak transitions
in hadron colliders since the CLEO and ARGUS experiments are signi?cantly im-proving the statistics of these processes.The key physics goal here is to obtain the
highest precision determination of V cb possible.This requires exploiting the heavy
quark symmetry result,together with QCD and1/M corrections,which?xes at
special kinematic point w=v·v′→1the normalization of the Isgur–Wise function. The normalization ofξ(w→1)is known to a precision approaching3%.10Therefore,
the goal of experiment should be to approach a3%determination of V cb.
Much e?ort to date has gone into the measurements of semileptonic weak in-
clusive decays and exclusive decays of heavy mesons.In e+e?experiments such as
CLEO or ARGUS,and as proposed for the asymmetric B–factory,one tunes the beam energy to produce theΥ(4S)resonance,which decays to pairs of B+B?or B0
dw =
G2F
w2?1(F D i(r,w))(7)
where r=m D
i /m B and F D
i
(r,w)is a form factor.10In the m B,D→∞limit F
is given in terms of the Isgur–Wise functionξ(w)and the known ratio r.At the special“zero recoil”pointξ(1)=1+?where?is composed of(a)QCD corrections computed to NLLA order±1%and(b)1/M e?ects that are dominant±3%.Hence,
the strategy is to extract the functional dependence of F (r,w ),or ξ(w )upon w and extrapolate to w =1where theoretical corrections are under control.This implies that the experimental statistical uncertainties must become signi?cantly smaller than ～1%and the limiting attainable precision of V cb is expected to be ～3%,modulo improvements in the theoretical uncertainties.
Neubert 10has carried out this analysis with the existing CLEO and ARGUS data on the q 2distributions,based upon ～(a few 100)events,to extract the model independent result |V cb |=0.042±0.007.This is indicative of the current statistical extrapolation errors attained with ～300events,and this should improve in the near future.It would appear that with 104fully reconstructed events the statistical error in this approach will scale downward by a factor of 10.The key point here is that the theoretical modeling in the hadronic environment is now relegated to the corrections,and not to the result itself.The highest experimental statistics will drive the future determinations of V cb .
The challenge for this approach in the hadronic experiments is the requirement to fully reconstruct the decaying B –meson,particularly with respect to kinematics.In e +e ?experiments the the beam energy,together with the ?ight direction of the B ,supplies su?cient kinematic information to know the B energy unambiguously.In the broad–band hadronic environment we are a priori limited to knowing only the ?ight 3–vector of the B ,and the visible 4–momenta;the unobserved neutrino momentum leads to the ambiguity.
Let us consider the semileptonic decay B →D +?±+X .Of course,X contains the neutrino but may also contain missing neutrals as well.The ?rst question is,can we select events in which w →1using this information alone?If we consider events for which we hypothesize that the missing (mass)2is M 2X ,then the energy of the B is determined up to a a two–fold ambiguity.
E B =?2E vis ±[?4E 2vis ?(E 2vis
? p 2vis cos 2θ)(?4+M 2B p 2vis cos 2θ)]1/22(M 2B +M 2vis ?M 2X ).
x = p p / M D B 2y = p p / M B B
B 2.....1/2 M /2M D B 221/2 M /2M D B _.
1/2+ M /2M D B 2D
B M / M a b
c m = M vis 2B M D
m = M vis 22B
m = M vis 22D _
Figure2:The phase space for B→D+?+ν(M2X=0)in the variables x～
E D/M B,y～E?/M B.The phase space is bounded by the points(a)(?andνback-
to-back),(b)(D and?back-to-back),and(c)(D andνback-to-back).The point(a)
corresponds to w=v D·v B=1.
θis the angle subtended by the?ight vector of the B(primary to secondary vertex vector)and p vis.Let us now further assume M X=0(no missing neutrals,etc.).To observe w=v D·v B=1we must have in the B rest–frame,M B=M D+2E?,i.e., the massless leptons are back–to–back,whence
M2vis=(p D+p?)2=M2D+2M D E?=M D M B(9) The condition M2vis=M D M B,using,
0=M2X=(p D+p??p B)2implies x+y=1
M B
2 M B2
reconstruction for a(few)×103events.However,we would prefer a method which is e?cient,covers all of phase space,not just p vis=0,and ideally which o?ers greater leverage in momentum resolution.
Perhaps we can exploit the fact that a fraction f～20%of B–mesons will be produced as the daughters of the B??resonance,together with the daughter pion.Thus,let us ask if we can select the B–meson energy in a typical process B→D?+?+ν,where the two hypothetical4–momenta of the B are p(1)μ,p(2)μ.We demand that we?nd a pion which matches a hypothetical solution for the B–meson 4–momentum,p B,satisfying either:
(pπ+p(1)B)2=M2B??or(pπ+p(2)B)2=(M B??+δM B??)2(12) whereδM B??is the width of the resonance parent.Then a di?erence between the hypothetical4–momentum has a resolution given by the width:
pμπ(p(1)B?p(2)B)=M B??δM B??=Eπ(δr E B)(1?(1+β?β2)cosθ)(13) whereδr E B is the minimum resolvable B–energy.Hence,apparently we can directly reconstruct the B energy by this method to a limiting resolution of only:
δr E B
Eπ
>～5%(14)
where we use Eπ～1GeV,δM B??～50MeV,typically,andθ≈90o.On the other hand,we see in eq.(11)that,using p vis the energy ambiguity is:
δE B=| p vis| M B
2(M B?M D).The value
δr E B is then su?ciently small to allow a selection between the two solutions,since:
δr E B
Eπ| p vis|
M B
2(M B?M D).In other words,the energy ambiguity can be～10σ
of the minimum resolvable energy of the B–meson,using the daughter pion in combination.
Note that we are not then restricted to the special kinematic con?gurations | p vis|=0;indeed,this approach would be complimentary to| p vis|=0,and prefer-ably requires that| p vis|be large.It does rely on being able to“cut hard”to reduce the background pions that fake a B??daughter,and it is subject to background fakes that favor the wrong solution.This probably favors low p T B’s with less of an enveloping jet structure,and then a<θ50%cut.Again,this cannot resolve the missing collinear pion ambiguity,but it is potentially able to resolve the typical
missing neutral pion ambiguity.We have given here only a sketchy analysis of this.It requires serious study by Monte Carlo simulation,or direct application to the existing data of charm photoproduction experiments,and eventually in B decays where the B –momentum is known (all decay products visible).With f ～10%we may hope to be able to select between kinematic options with e?ciencies of order 1%,allowing ～107fully reconstructed semileptonic weak decays.
2.5.Semileptonic Weak Decays involving V ub
High statistics measurements of exclusive semileptonic branching ratios such as B →?+ν+(
BV ub may be possible.The quantity f B √
Mode
yield /1010B ’s 5.0×10?5
?lattice 2.5×10?4
inclusive models 1.0×10?6
2.7×10?7
3.0×10?5
?chiral symmetry 1.0×10?7
chiral symmetry 10?4
Argus limit <～1%3×10?5
?yields f B s /f B (u,d )
5×10?5∝f B s
ρmass,and connect to the lepton at the decay vertex of the B.The estimated Br(B?→ρl?ν)～(Br(B?→D?l?ν)～4%)×|V bu/V bc|2×1/2～5.0×10?5, thus with1010produced B’s we will have～1.5×105events.The problematic backgrounds are from B→D?νand D→2πor D→ρπ0,with theπ0undetected, B→ρD and D→?ν.Theρtends to be diluted by the pion background,which may require cutting on events in which the other B is seen in a semileptonic mode (～10%).The rejection ofγ’s and the mass reconstruction of theρ,and a veto on more than2pions are important constraints to consider in?shing theρout of hadronic events.
Thus,a high statistics study of Cabibbo suppressed decay modes seems possible with1010B–mesons,but we are in a learning situation at present that must evolve considerably.This yields of order105decays.A form factor analysis may be possible for theπ?νmode if daughter pion kinematic tagging is possible,yielding～103fully reconstructed decays.One can hope to exploit the fact that chiral symmetry?xes the normalization of this matrix element at w=1.It should certainly be possible to achieve V ub to better than±20%using models,and perhaps better precision by use of chiral symmetry.The quantity f Bs/f Bu,d would be probed to±1%precision.
2.6.B s and B c
The B s=(
B s.This will allow survey of various decay modes,such as DK?,D?K,D?S D?S,D?S?ν,etc. Also,of great interest will be the study of higher resonances producing daughter K–mesons in association with the B s,e.g.,
p
B s mixing,is discussed below.
Table III.(a)Yields are for detectable decays and include the branching fractionsψ→
μ+μ?～7%(b)includes(ψ→μ+μ?)×(D?s→π+(φ→K+K?)～2%).
Br yield/100pb?1
B c→π+ψ2.8×103(a)
B c→D?sψ7.0×102(b)
B c→ψ?ν7.0×104(a)
Perhaps the most interesting new mesonic system will be the B c=(
The prospects for observation of B c hinge upon the production cross-section.There is reasonable agreement amongst several groups14that the ratioσ(B c)/σ(
Qq.
The spectrum of QQq baryons is thus related to the spectrum of mesons con-
taining a single heavy antiquark.The groundstate is essentially a(1,1
2)
heavy spin multiplet.The form factors describing the semileptonic decays of these objects may be directly related to the Isgur-Wise function,which arises in the semileptonic decay of heavy mesons.The production rates for baryons of the form ccq,bbq and bcq have been estimated in the approximation that the QQ diquark is formed?rst by perturbative QCD interactions,and then this system fragments to form the baryon like a heavy meson.15(In the cc system the heavy diquarks are not particularly small relative to1/Λ,so there may be sizeable corrections to these results).Essentially the fragmentation of a heavy quark Q into a QQq(or QQ′q)baryon factorizes into short-distance and long-distance contributions.The heavy quark?rst fragmentation into a heavy diquark may be trivially related to the fragmentation of Q into quarkonium Q
analyzed recently by Braaten,et al.,and others14,15The subsequent fragmentation of the diquark QQ to a baryon is identical to the fragmentation of a
Qq.15Experimental data on production of heavy mesons can be used here.
Table IV.Hadronically produced double heavy baryons for Tevatron(3×109B u,d’s)
and Main Injector(3×1010B u,d’s).
Tevatron
Σcc,Σ?cc6×105
Λbc6×105
Σbc,Σ?bc～106
Σbb,Σ?bb～104
Λbc6×103
Σbc,Σ?bc6×103
The probability for c→Σcc,Σ?cc is estimated to be～2×10?5,for b→Λbc to be～2×10?5,and for b→Σbc,Σ?bc to be～3×10?5.The probabilities for b→Σbb,Σ?bb,c→Λbc and c→Σbc,Σ?bc are down by roughly(m c/m b)3,or two orders of magnitude.
Detection of these objects is probably very di?cult at best.Consider theΣbb decay chain:
Σbb→D?+X+(Σbc
→D?+X+(Λb
→D?+X+(Λc
→K?+X+Λ(19) Each vertex above must be reconstructed,in spite of a high probability of missing neutrals,including the drift of D?→D’s away to branch vertices.A rough esti-mate is that a handful of such decay chains might be available in a1010program admitting reconstruction of the parent doubly–heavy baryon.However,there will come insights as to how to do this well as experience is gained.
3.Rare Processes
In this section we will brie?y discuss some of the interesting“rare”processes that are the far–reaching goals of the initiatives of this decade.Much greater detail is a?orded these topics in other talks in this conference,so we will focus only on issues that involve some of the aforementioned ideas.Clearly the ultimate structure of CP–violation is of great interest,but the?rst observation of CP–violation in the B-system will be an achievement of enormous importance.We will comment as to how this observation may be feasible in the hadronic collider mode by making use of daughter pion?avor tagging,in comparison to the conventional strategy.Indeed, many of the tools necessary to see the CP–asymmetry in B→ψK S are now in place at CDF,and this exciting observation may be only a few years away!
We describe the important observation of B s
B0)→ψK S involves CP–violation.Thus the partial widths for B0and
B→ψK S)?Γ(B→ψK S) B→ψK S)+Γ(B→ψK S)=
x d
B+)it can decay
semileptonically to a charge?(+)lepton,with a Br(B→?νD)～10%.This does not require full reconstruction of the semileptonic decay,so for CP–violation one is e?ectively measuringΓ(?+ψK S)?Γ(??ψK S)(Note that this does not require a new single lepton trigger since one can trigger on theψdimuons).Including geometric e?ciencies this conventional tagging e?ciency is expected to be of order?1～10?2.
Gronau,Nippe and Rosner3have pointed out that resonance daughter pions (as well as rapidity correlations associated with the jet fragmentation)are possi-ble?avor–tags.A stunning implication of the daughter mesons from parent reso-nances is that all CP–violating processes in hadron machines are expected to be self–tagging!We should recognize that at low–p T the b–production mechanism is somewhat more akin to threshold production and the resonance mechanism may be favored.
Table V.Statistical signi?canceσi for tagging e?ciencies?1,?2and asymmetries a,
for various integrated luminosities.We show the100pb?1,i.e.,prospects for run I(b) at Fermilab(1010B’s corresponds to L dt=103pb?1).
?2??1σ2?σ1
0.5100pb?1
0.1100pb?1
0.5103pb?1
0.1103pb?1
0.5104pb?1
0.1104pb?1
At higher p T the b–jet is forming and there would be more pions expected(a source of dilution),and perhaps the rapidity correlation idea is favored.This is not to advocate any theory of production,but rather to emphasize that the optimization may involve tuning of p T,etc.For example,we may prefer operating at low p T’s below the present cuts.While with optimization cuts it is possible that signi?-cant improvements in the tagging e?ciency may occur,the charm photoproduction experiments suggest that a tagging e?ciency of?2～10%from daughter pions is possible.The?avor of a neutral B0～B0～b
B s Mixing
We have for the mixing parameter:
x s=G2F m B
s
τB
s
B
/Γ～(14±6)(f Bs/200MeV)2(21)
where F(z)is an Inami-Lim function.An expression for x d is gotten by replacing s
by d everywhere.Note that:
x s
V td 2(1+δ)δ=
m B s f2B s
Bf B=200MeV(23) x s～17.0?40.0,m t=200GeV;√
2(radians)/(e-
attenuation),thus x=10corresponds to20radians per decay length).This requires observing the time evolution of the system,which implies that fully reconstructed (energy and?avor),tagged B s decays are necessary.In contrast,x d=0.66and is readily observed in time–integrated measurements.These requirements make the observation of B s
2(24) Withδxy～40μm,L xy～600μm,we?ndσt～0.07characteristic of CDF-SVX. The conventional triggers would use a produced B s→lν(D s→φX)or B s→π+π?π+(D s→φX)and the opposite B→lνX for?avor tagging.By fully recon-structing the B s decay(requiring exclusively charged particles in X)and partially reconstructing the tagging decay,it has been estimated that one can reconstruct the oscillation inτwith～4000events.1With the estimated e?ciencies this requires about3×1010to1011produced B’s.This appears to be a signi?cant challenge!
Can we tag the B s?avor and kinematics by using the daughter K mesons asso-ciated with it’s resonance production?For example,we expect the D-wave B(2?) and B(3?)to be above threshold for decay to K++B s or K?+
charm system process D??s→D?K has been demonstrated,5which is the opposite to D???s→D s K,The higher resonances have not yet been seen.
3.3.Other Rare Modes
Length considerations preclude our giving any comprehensive discussion of the additional interesting rare modes in B-physics.We will,however,brie?y mention a few of the leptonic modes.Rare B decays encompass such processes as:
(I)B d,s→(eμ,τ
μ,μτ)(25) and additional hadrons in the?nal state may be included.We should remark that theτcontaining?nal states are unique to B,never available in K decays,and at best phase space suppressed for D’s.
Such processes as(I)have low standard model rates and are probes of V td,V ts, and m t.Thus,they are good probes of the standard model if they are seen at the expected rates.Moreover,they are excellent probes of new physics,such as charged Higgs and?avor changing neutral Higgs couplings,which are generally∝mass.The conventional SM estimates are as follows:
Table VI.Rare leptonic mode branching ratios.
τμe
10?710?14
5.0×10?95.0×10?16
μ.Since the signature is a clean displaced muon pair event with mass reconstruction,it is likely that this can be searched over a rapidity range of|η|<～3,and a p t threshold of O(5)GeV/c.
Valencia and Willenbrock(VW)have given a nice characterization of the lepton–number violating processes(class II,above)which we describe here.First,note that (τe)and(τμ)are unique to the B-system(not available in rare K decays).Since such processes can be generated in principle by Higgs-scalar exchange,which is a coupling constant∝mass,it is possible that the B system becomes sensitive to these processes at a level that is readily experimentally accessible,and complimentary to rare K decay searches,such as at KTEV.
VW begin by postulating general four–fermion interactions describing such pro-cesses as B→eμand K→eμas:
c B(μΓe)+c K(μΓe)(26) with arbitray Dirac structuresΓ.VW then consider the e?ects of di?erentΓ’s an
d c X’s on th
e ratio o
f branchin
g ratios R1=Br(B→μe)/Br(K L→μe)and
R2=Br(B→μe+h)/Br(K L→μe+h)(where h is an extra hadron system,e.g., pions)as follows:
R1≈c2B f2B m
τK ≈10?4c2B
K
c2K f2K m3BτB c2KΓ=(1,γ5)
R2≈c2B f2B m5
τK ≈c2B
K
in on at的时间用法和地点用法 完全版
in，on，at的时间用法和地点用法 一、in, on, at的时间用法 ①固定短语： in the morning/afternoon/evening在早晨/下午/傍晚, at noon/night在中午/夜晚, （不强调范围，强调的话用during the night） early in the morning=in the early morning在大清早， late at night在深夜 on the weekend在周末（英式用at the weekend在周末，at weekends每逢周末） on weekdays/weekends在工作日/周末， on school days/nights在上学日/上学的当天晚上， ②不加介词 this, that, last, next, every, one, yesterday, today, tomorrow, tonight，all，most等之前一般不加介词。如， this morning 今天早晨 （on）that day在那天（that day更常用些） last week上周 next year明年 the next month第二个月（以过去为起点的第二个月，next month以现在为起点的下个月） every day每天 one morning一天早晨 yesterday afternoon昨天下午 tomorrow morning明天早晨 all day/morning/night整天/整个早晨/整晚（等于the whole day/morning/night） most of the time （在）大多数时间 ③一般规则 除了前两点特殊用法之外，其他≤一天，用on，＞一天用in，在具体时刻或在某时用at（不强调时间范围） 关于on 生日、on my ninth birthday在我九岁生日那天 节日、on Teachers’Day在教师节 （注意：节日里有表人的词汇先复数再加s’所有格，如on Children’s Day, on Women’s Day, on Teachers Day有四个节日强调单数之意思，on Mother’s Day, on Father’s Day, on April Fool’s Day, on Valenti Day） 星期、on Sunday在周日，on Sunday morning在周日早晨 on the last Friday of each month 在每个月的最后一个星期五 日期、on June 2nd在六月二日 on the second (of June 2nd) 在六月的第二天即在六月二日 on the morning of June 2nd在六月二日的早晨，on a rainy morning在一个多雨的早晨 on a certain day 在某天 on the second day在第二天（以过去某天为参照） 注意：on Sunday在周日，on Sundays每逢周日（用复数表每逢之意），every Sunday每个周日，基本一个意思。 on a school day 在某个上学日，on school days每逢上学日。on the weekend在周末，on weekends每逢 周末。 关于in in June在六月 in June, 2010在2010年六月
常用标点符号用法简表.doc
常用标点符号用法简表 标点符号栏目对每一种汉语标点符号都有详细分析，下表中未完全添加链接，请需要的同学或朋友到该栏目查询。名称符号用法说明举例句号。表示一句话完了之后的停顿。中国共产党是全中国人民的领导核心。逗号，表示一句话中间的停顿。全世界各国人民的正义斗争，都是互相支持的。顿号、表示句中并列的词或词组之间的停顿。能源是发展农业、工业、国防、科学技术和提高人民生活的重要物质基础。分号；表示一句话中并列分句之间的停顿。不批判唯心论，就不能发展唯物论；不批判形而上学，就不能发展唯物辩证法。冒号：用以提示下文。马克思主义哲学告诉我们：正确的认识来源于社会实践。问号？用在问句之后。是谁创造了人类？是我们劳动群众。感情号①！1.表示强烈的感情。2.表示感叹句末尾的停顿。战无不胜的马克思主义、列宁主义、毛泽东思想万岁！引号 ②“ ” ‘ ’ ╗╚ ┐└1.表示引用的部分。毛泽东同志在《论十大关系》一文中说：“我们要调动一切直接的和间接的力量，为把我国建设成为一个强大的社会主义国家而奋斗。”2.表示特定的称谓或需要着重指出的部分。他们当中许多人是身体好、学习好、工作好的“三好”学生。 3.表示讽刺或否定的意思。这伙政治骗子恬不知耻地自封为“理论家”。括号③（）表示文中注释的部分。这篇小说环境描写十分出色，它的描写（无论是野外，或是室内）处处与故事的发展扣得很紧。省略号④……表示文中省略的部分。这个县办工厂现在可以生产车床、电机、变压器、水泵、电线……上百种产品。破折号⑤——1.表示底下是解释、说明的部
分，有括号的作用。知识的问题是一个科学问题，来不得半点的虚伪和骄 傲，决定地需要的倒是其反面——诚实和谦逊的态度。2.表示意思的递进。 团结——批评和自我批评——团结3.表示意思的转折。很白很亮的一堆洋 钱！而且是他的——现在不见了！连接号⑥—1.表示时间、地点、数目等 的起止。抗日战争时期（1937-1945年）“北京—上海”直达快车2.表 示相关的人或事物的联系。亚洲—太平洋地区书名号⑦《》〈〉表示 书籍、文件、报刊、文章等的名称。《矛盾论》《中华人民共和国宪法》《人 民日报》《红旗》杂志《学习〈为人民服务〉》间隔号·1.表示月份和日期 之间的分界。一二·九运动2.表示某些民族人名中的音界。诺尔曼·白求 恩着重号.表示文中需要强调的部分。学习马克思列宁主义，要按照毛泽 东同志倡导的方法，理论联系实际。······
In on at 时间用法及练习
In\ on\ at (time) at 用在具体某一时刻eg at 11:00 at 4:30 在节假日的全部日子里at Christmas 习惯用法at noon at weekends\ at the weekend at night at breakfast\lunch\supper on 具体到某一天；某一天的早晨，中午或晚上on May the first on Sunday morning 对具体某一天的早晨，中午，晚上进行详细的描述on a sunny morning on a windy night 节日的当天；星期on Women?s Day on Monday In 用在年；月；季节in spring in 2012 in August 后面+一段时间表示将来时in two days 习惯用法in the morning\in the afternoon\in the evening “\”以this, that, last, next, some, every, one, any,all开始的时间副词之前的at\on\in 省略在today, tomorrow, yesterday, the day after tomorrow, tomorrow morning，yesterday afternoon，the day before yesterday 之前的介词必须省略 Practice ___ summer ____ 2012 ____ supper ___ 4:00 ___ June the first ___yesterday morning ____ New Year?s Day ___ Women?s Day ___ the morning ____ the morning of July the first ____ 2014 ___ tomorrow morning ____ midnight 1.—What are you doing ____ Sunday? And what is your wife doing ___ the weekend? 2. He?ll see you ____ Monday. And he…ll see your brother ____next Monday. 3. They often go out ___ the evenings. But they don?t go out ____ Sunday evenings. 4. Do you work ____ Fridays? Does she work _____ every Friday? 5. They usually have a long holiday ___ summer. But their son can only have a short holiday ___ Christmas. 6. Paul got married ___ 2010, He got married ___ 9 o?clock ___ 19 May 2010. His brother got married ___ May, 2011. His sister is getting married ___ this year. 1.—When will Mr Black come to Beijing? ---_______ September 5 A. on B. to C. at D. in 2. The twins were born ____ a Friday evening. A. on B. of C. at D. in 3. It?s the best time to plant ____ spring. A. on B. in C. at D.\ 4. ____ the age of twelve, Edison began selling newspaper on train. A. On B. At C. In D.By 5. She has been an English teacher ____ 2000. A. for B. since C. in D.on 6.I have studied English _____ 2003. A. since B. for C. from D.in
常用标点符号用法含义
一、基本定义 句子，前后都有停顿，并带有一定的句调，表示相对完整的意义。句子前后或中间的停顿，在口头语言中，表现出来就是时间间隔，在书面语言中，就用标点符号来表示。一般来说，汉语中的句子分以下几种： 陈述句： 用来说明事实的句子。 祈使句： 用来要求听话人做某件事情的句子。 疑问句： 用来提出问题的句子。 感叹句： 用来抒发某种强烈感情的句子。 复句、分句： 意思上有密切联系的小句子组织在一起构成一个大句子。这样的大句子叫复句，复句中的每个小句子叫分句。 构成句子的语言单位是词语，即词和短语（词组）。词即最小的能独立运用的语言单位。短语，即由两个或两个以上的词按一定的语法规则组成的表达一定意义的语言单位，也叫词组。 标点符号是书面语言的有机组成部分，是书面语言不可缺少的辅助工具。它帮助人们确切地表达思想感情和理解书面语言。 二、用法简表 名称
句号① 问号符号用法说明。？1．用于陈述句的末尾。 2．用于语气舒缓的祈使句末尾。 1．用于疑问句的末尾。 2．用于反问句的末尾。 1．用于感叹句的末尾。 叹号！ 2．用于语气强烈的祈使句末尾。 3．用于语气强烈的反问句末尾。举例 xx是xx的首都。 请您稍等一下。 他叫什么名字？ 难道你不了解我吗？为祖国的繁荣昌盛而奋斗！停止射击！ 我哪里比得上他呀！ 1．句子内部主语与谓语之间如需停顿，用逗号。我们看得见的星星，绝大多数是恒星。 2．句子内部动词与宾语之间如需停顿，用逗号。应该看到，科学需要一个人贡献出毕生的精力。 3．句子内部状语后边如需停顿，用逗号。对于这个城市，他并不陌生。 4．复句内各分句之间的停顿，除了有时要用分号据说苏州园林有一百多处，我到过的不外，都要用逗号。过十多处。 顿号、用于句子内部并列词语之间的停顿。
2时间介词in,on,at的用法
介词in on at 表示时间的用法及区别 Step1 Teaching Aims 教学生掌握时间介词in,on和at的区别及用法。 Step2 Teaching Key and Difficult Points 教学生掌握时间介词in,on和at的区别及用法。 Step3 Teaching Procedures 1.用in的场合后所接的都是较长时间 (1)表示“在某世纪/某年代/特定世纪某年代/年/季节/月”这个含义时，须用介词in Eg: This machine was invented in the eighteenth century. 这台机器是在18世纪发明的。 、 She came to this city in 1980. 他于1980年来到这个城市。 It often rains here in summer. 夏天这里常常下雨。 (2)表示“从现在起一段时间以后”时，须用介词in。(in+段时间表将来) Eg: They will go to see you in a week. 他们将在一周后去看望你。
I will be back in a month. 我将在一个月后回来。 (3)泛指一般意义的上、下午、晚上用in, in the morning / evening / afternoon Eg: They sometimes play games in the afternoon. 他们有时在下午做游戏。 Don't watch TV too much in the evening. 晚上看电视不要太多。（4）A. 当morning, evening, afternoon被of短语修饰，习惯上应用on, 而不用in. Eg: on the afternoon of August 1st & B. 但若前面的修饰词是early, late时，虽有of短语修饰，习惯上应用in, 而不用on. Eg: in the early morning of September 10th 在9月10的清晨； Early in the morning of National Day, I got up to catch the first bus to the zoo. 国庆节一清早，我便起床去赶到动物园的第一班公共汽车。 2.用on的场合后所接的时间多与日期有关 （1）表示“在具体的某一天”或（在具体的某一天的）早上、中午、晚上”，或“在某一天或某一天的上午，下午，晚上”等，须用介
介词in-on-at在表示时间时的用法
介词in, on, at在表示时间时的用法区别 ①in时间范围大（一天以上）如：in Tanuary, in winter, in 1999;泛指在上午，下午，晚上，如：in the morning(afternoon, evening). 习惯用法：in the daytime 在白天。 ②on指在某一天或某一天的上午，下午，晚上，如：on Monday, on Sunday afternoon, on July 1, 1999 ③at时间最短，一般表示点时间，如at six o’clock, at three thirty.习惯用法：at night, at noon, at this time of year. in, on和at在表达时间方面的区别 in 表示在某年、某季节、某月、某周、某天和某段时间 in a year在一年中 in spring 在春季 in September 在九月 in a week 在一周中 in the morning/afternoon/evening 在上午/下午/傍晚 但在中午，在夜晚则用at noon/night on 表示某一天或某一天的某段时间 on Monday 在周一 on Monday afternoon 在周一下午 on March 7th 在3月7日 on March 7th, 1998. 在1998年3月7日 on the morning of March 7th, 1998. 在1998年3月7日上午
at 表示某个具体时刻。 at eight o’clock 在8点钟 at this time of the year 在一年中的这个时候 at the moment 在那一时刻 at that time 在那时 注意：在英语中，如果时间名词前用this, last, next 等修饰时，像这样的表示，“在某时”的时间短语前，并不需要任何介词。 例如：last month, last week, this year, this week, next year, the next day, the next year 等。 1．What’s the weather like in spring/summer/autumn/winter in your country? 你们国家春天/夏天/秋天/冬天的天气怎么样？ in 在年、月、周较长时间内 in a week 在里面 in the room 用某种语言 in English 穿着 in red on 某日、某日的上下午on Sunday afternoon 在……上面 on the desk 靠吃……为生live on rice 关于 a book on Physics 〔误〕We got to the top of the mountain in daybreak. 〔正〕We got to the top of the mountain at day break. 〔析〕at用于具体时刻之前，如：sunrise, midday, noon, sunset, midnight, night。〔误〕Don't sleep at daytime 〔正〕Don't sleep in daytime. 〔析〕in 要用于较长的一段时间之内，如：in the morning / afternoon, 或in the week / month / year. 或in spring / supper /autumn / winter等等。 〔误〕We visited the old man in Sunday afternoon. 〔正〕We visited the old man on Sunday afternoon. 〔析〕in the morning, in the afternoon 如果在这两个短语中加入任何修饰词其前面的介
inonat的时间用法和地点用法版
精心整理in，on，at的时间用法和地点用法 一、in,on,at的时间用法 1、固定短语： inthemorning/afternoon/evening在早晨/下午/傍晚, 2 （on thenextmonth第二个月（以过去为起点的第二个月，nextmonth以现在为起点的下个月） everyday每天 onemorning一天早晨 yesterdayafternoon昨天下午
tomorrowmorning明天早晨 allday/morning/night整天/整个早晨/整晚（等于thewholeday/morning/night）mostofthetime（在）大多数时间 3、一般规则 除了前两点特殊用法之外，其他≤一天，用on，＞一天用in，在具体时刻或在某时用at（不强调时间范围） 关于 On 1 2) 3) （注意：节日里有表人的词汇先复数再加s’所有格，如 onChildren’sDay,onWomen’sDay,onTeachers’Day有四个节日强调单数之意思，onMother’sDay,onFather’sDay,onAprilFool’sDay,onValentine’sDay） 星期、onSunday在周日，onSundaymorning在周日早晨onthelastFridayofeachmonth在每个月的最后一个星期五
日期、onJune2nd在六月二日 onthesecond(ofJune2nd)在六月的第二天即在六月二日onthemorningofJune2nd在六月二日的早晨，onarainymorning在一个多雨的早晨 onacertainday在某天 onthesecondday在第二天（以过去某天为参照） 关于 In 1 2) InJune在六月 inJune,2010在2010年六月 in2010在2010年 inamonth/year在一个月/年里（在将来时里翻译成一个月/年之后） inspring在春天
常用标点符号主要用法
常用标点符号主要用法 问号 1、用在特指问句后。如：(7)你今年多大了？ 2、用在反问句后。如：(8)为什么我们不能刻苦一点呢？ ?提示：反问句若语气缓和，末尾可用句号；若语气重可用感叹号。如：(9)国家 主席可以活活被整死；堂堂大元帅受辱骂；……这哪里还有什么尊重可言！ 3、用在设问句后。如：(10)我们能让你计划实现吗？不会的。 4、用在选择问句中。如：(11)我们是革命呢，还是要现大洋？ ( 12)你到底是去，还是不去？ 5、用在表疑问的独词句后。如：(13)我？不可能吧。 ?提示：若疑问句为倒装句，问号应放在句末。如：(14)到底出了什么问题，你的 车？(若说成：“到底出了什么问题？你的车。”则错误。) ?特别提示： 句号、问号均表示句末停顿。句号用于陈述句末尾，问号用于疑问句末尾。有些句 中虽有疑问词，但全句并不是疑问句，句末只能用句号，不能用问号。 例如：(17)……最后应求出铜块的体积是多少？ (18)面对千姿百态、纷繁芜杂的期刊世界，有哪位期刊编辑不想通过期刊版面设 计为刊物分朱布白、添花增色呢？ (19)关于什么是智力？国内外争论多年也没有定论。 (17) (18) ( 19)三句都是非疑问句，(17) (18)句中问号均应改为句号，(19)句中的问号应改为逗号。 感叹号 ?特别提示： 1、在表感叹或祈使语气的主谓倒装句中，感叹号要放在句末。 如：(20)多么雄伟壮观啊，万里长城！ 2、句前有叹词，后是感叹句，叹号放在句末。 如：(21)啊，这儿多么美丽！ 下面介绍句中点号的用法。句中点号包括逗号、分号、顿号、和冒号四种。 逗号 提示：复句内各分句之间的停顿，除了有时用分号外，都要用逗号。 顿号 用于句中并列的词、词组之间较小的停顿。 如：(22)邓颖超的品德、人格、风范为中华民族树立了一座精神丰碑。 (23)从1918年起，鲁迅陆续发表了《狂人日记》、《药》、《祝福》等短篇小说。 ?特别提示：以下九种情况不用顿号。 1、不定数的两个数字间不用顿号。 如：(24)你的年龄大概是十六七岁。(不能写成“十六、七岁”) ?【注意】相邻的两个数字而非约数之间要用顿号。
inonat的时间用法和地点用法版
i n o n a t的时间用法和 地点用法版 集团档案编码：[YTTR-YTPT28-YTNTL98-UYTYNN08]
i n，o n，a t的时间用法和地点用法 一、in,on,at的时间用法 1、固定短语： inthemorning/afternoon/evening在早晨/下午/傍晚, atnoon/night在中午/夜晚,（不强调范围，强调的话用duringthenight）earlyinthemorning=intheearlymorning在大清早， lateatnight在深夜 ontheweekend在周末（英式用attheweekend在周末，atweekends每逢周末）onweekdays/weekends在工作日/周末， onschooldays/nights在上学日/上学的当天晚上， 2、不加介词 this,that,last,next,every,one,yesterday,today,tomorrow,tonight，all，most等之前一般不加介词。如， thismorning今天早晨 （on）thatday在那天（thatday更常用些） lastweek上周 nextyear明年 thenextmonth第二个月（以过去为起点的第二个月，nextmonth以现在为起点的下个月） everyday每天 onemorning一天早晨 yesterdayafternoon昨天下午 tomorrowmorning明天早晨
allday/morning/night整天/整个早晨/整晚（等于 thewholeday/morning/night） mostofthetime（在）大多数时间 3、一般规则 除了前两点特殊用法之外，其他≤一天，用on，＞一天用in，在具体时刻或在某时用at（不强调时间范围） 关于on On指时间表示： 1）具体的时日和一个特定的时间，如某日，某节日，星期几等。Hewillcometomeetusonourarrival. OnMay4th(OnSunday,OnNewYear’sday,OnChristmasDay),therewillbeacelebra tion. 2)在某个特定的早晨，下午或晚上。 Hearrivedat10o’clocko nthenightofthe5th. Hediedontheeveofvictory. 3)准时，按时。 Iftherainshouldbeontime,Ishouldreachhomebeforedark. 生日、onmyninthbirthday在我九岁生日那天 节日、onTeachers’Day在教师节 （注意：节日里有表人的词汇先复数再加s’所有格，如 onChildren’sDay,onWomen’sDay,onTeachers’Day有四个节日强调单数之意思， onMother’sDay,onFather’sDay,onAprilFool’sDay,onValentine’sDay）星期、onSunday在周日，onSundaymorning在周日早晨
精华版+in,+at,+on表时间的用法
介词in,on与at表时间的用法 at < 天(eg. noon, dawn, night, one’ clock) on = 天(Monday, 30th June, New Year’s Day, Mother’s Day) in > 天(2008, summer, April, 还有早午晚) 用in的场合后所接的都是较长时间 (1)表示“在某世纪/某年代/特定世纪某年代/年/季节/月”这个含义时,须用介词in Eg: This machine was invented in the eighteenth century. 这台机器是在18世纪发明的。 This incident happened in the 1970s. 该事件发生在20世纪70年代。 She came to this city in 1980. 他于1980年来到这个城市。 It often rains here in summer. 夏天这里常常下雨。 (2)表示“从现在起一段时间以后”时,须用介词in。(in+段时间表将来) Eg: They will go to see you in a week. 他们将在一周后去看望你。 I will be back in a month. 我将在一个月后回来。 (3)泛指一般意义的上、下午、晚上用in, in the morning / evening / afternoon Eg: They sometimes play games in the afternoon. 他们有时在下午做游戏。
Don't watch TV too much in the evening. 晚上看电视不要太多。 (4)A. 当morning, evening, afternoon被of短语修饰,习惯上应用on, 而不用in. Eg: on the afternoon of August 1st (5)B. 但若前面的修饰词是early, late时,虽有of短语修饰,习惯上应用in, 而不用on. Eg: in the early morning of September 10th 在9月10的清晨; in the late afternoon of September 12th 在9月12日的傍晚。 Early in the morning of National Day, I got up to catch the first bus to the zoo. 国庆节一清早,我便起床去赶到动物园的第一班公共汽车。 用on的场合后所接的时间多与日期有关 (1)表示“在具体的某一天”或(在具体的某一天的)早上、中午、晚上”,或“在某一天或 某一天的上午,下午,晚上”等,须用介词on。 Eg: Jack was born on May 10th, 1982. 杰克生于1982年5月10日。 They left on a rainy morning. 他们是在一个雨天的早上离开的。 He went back to America on a summer afternoon. 他于一个夏天的下午返回了美国。
公文写作中标点符号的使用规范
公文写作中标点符号的使用规范 《中华人民共和国国家标准》（GB|T15834—1995）中有《标点符号用法》，其中对标点符号的使用作了明确的规定： 标点符号是辅助文字记录语言的符号，是书面语的有机组成部分，用来表示停顿、语气以及词语的性质和作用。 常用的标点符号有16种，分点号和标号两大类。 点号的作用在于点断，主要表示说话时的停顿和语气。点号又分为句末点号和句内点号——句末点号用在句末，有句号、问号、叹号3种，表示句末的停顿，同时表示句子的语气；句内点号用在句内，有逗号、顿号、分号、冒号4种，表示句内的各种不同性质的停顿。 标号的作用在于标明，主要标明语句的性质和作用。常用的标号有9种，即：引号、括号、破折号、省略号、着重号、连接号、间隔号、书名号和专名号。 一、常用标点符号用法简表 名称符号用法说明举例 句号。表示一句话完了之后的停 顿。 中国共产党是全中国人民的领导核心。 逗号，表示一句话中间的停顿。全世界各国人民的正义斗争，都是互相支持的。 顿号、表示句中并列的词或词组 之间的停顿。 能源是发展农业、工业、国防、科学技术和提高人 民生活的重要物质基础。 分号；表示一句话中并列分句之 间的停顿。 不批判唯心论，就不能发展唯物论；不批判形而上 学，就不能发展唯物辩证法。 冒号：用以提示下文。马克思主义哲学告诉我们：正确的认识来源于社会实践。 问号？用在问句之后。是谁创造了人类？是我们劳动群众。 感情号！1.表示强烈的感情。 2.表示感叹句末尾的停 顿。 战无不胜的马克思主义、列宁主义、毛泽东思想万 岁！ 引号“”1.表示引用的部分。毛泽东同志在《论十大关系》一文中说：“我们要
七年级语文常用标点符号用法简表
七年级语文常用标点符号用法简表 七年级常用标点符号用法简表 一、基本定义 句子，前后都有停顿，并带有一定的句调，表示相对完整的意义。句子前后或中间的停顿，在口头语言中，表现出来就是时间间隔，在书面语言中，就用标点符号来表示。 二、复习标点符号的写法，明确标点符号的书写位置。 常用的标点符号有16种，分为点号和标号。 点号 句号 。 问号 ？ 感叹号 ！ 逗号 顿号 分号 ； 冒号 标号
引号“”‘’括号[] 破折号——省略号……书名号 着重号· 间隔号· 连接号— 专名号____ 备注占两格左上角
右上角 各占 一格 各占 一格 占两格 每格 三个点 占两格 标字下 标字间 占一格 标字下点号表示语言中的停顿，一般用在句中或句末。标号主要标明语句的性质和作用。 标点符号的书写位置。 在横行书写的文稿中，句号、问号、叹号、逗号、顿号、分号和冒号都占一个字的位置，放在句末的左下角。这七种符号通常不能放在一行的开头，因为这些符号表示语气的停顿，应该紧跟在一句话的末尾。如果一行的最后的一个格正好被文字占用了，那么这个标点就必须点标在紧靠文字的右下角。 引号、括号、书名号的前一半和后一半都各占一个字的
位置，它们的前一半可以放在一行的开头，但不出现在一行的末尾，后一半不出现在一行的开头。 破折号和省略号都占两个字的位置，可以放在一行的开头，也可以放在一行的末尾，但不可以把一个符号分成两段。这两种符号的位置都写在行次中间。） 引用之语未独立，标点符号引号外；引用之语能独立，标点符号引号里。 注意事项： 冒号 表示提示性话语之后的停顿，用来提引下文。 ①同志们，朋友们：现在开会了。 ②他十分惊讶地说：“啊，原来是你！” ③北京紫禁城有四座城门：午门、神武门、东华门和西华门。 注意：“某某说”在引语前，用冒号；在引语中或引语后，则不用冒号。如： ⑴老师说：“李白是唐代的大诗人，中学课本有不少李白的诗。” ⑵“李白是唐代的大诗人，”老师说，“中学课本里有不少李白的诗。” ⑶“李白是唐代的大诗人，中学课本里有不少李白的诗。”老师说。
时间介词(at, in ,on) 的用法
时间介词(at, in ,on) 的用法 1. at （1）时间的一点、时刻等。如： They came home at seven o’clock. (at night, at noon, at midnight, at ten o’clock, at daybreak, at dawn）. （2）后面接表示岁数的词。 Children in China start school at 6 years old. （3）较短暂的一段时间。可指某个节日或被认为是一年中标志大事的日子。如： He went home at Christmas （at New Year, at the Spring Festival）. 2. in （1）在某个较长的时间（如世纪、朝代、年、月、季节以及泛指的上午、下午或傍晚等） 内。如： in 2004, in March, in spring, in the morning, in the evening, etc （2）在一段时间之后,常用于将来时。 He will arrive in two hours. These products will be produced in a month. 3. on （1）具体的时日和一个特定的时间，如某日、某节日、星期几等。如： On Christmas Day（On May 4th）, there will be a celebration. （2）在某个特定的早晨、下午或晚上。如： He arrived at 10 o’clock on the night of the 5th. （3）准时，按时。如： If the train should be on time, I should reach home before dark. 表示频率的副词用法详解 一、常见的频率副词 always，usually，often，sometimes， seldom，never. 1) always表示的频率为100%，意思是"总是、一直、始终"。 I always do my cleaning on Sundays. 我总是在星期天搞卫生。 2）usually与always相比，表示的频率要低些，约为70%-80%。意思是"通常"。 Plants are usually green. 植物通常是绿色的。 Usually she goes to work by bus. 她通常乘公共汽车去上班。 3）often的频率比usually又略低些，约为60%-70%，意思是"经常"、"常常"。 Do you often write to them? 你常给他们写信吗？ Does Fred come here often? 弗雷德常来这儿吗？ 4）sometimes的频率比often又低些，约为50%＞sometimes＞30%，意思是“有时、不时”。(window.cproArray = window.cproArray || []).push({ id: "u3054369" }); 3
公文中的标点符号正确用法
公文中标点符号的正确用法 标点符号是公文语言的重要组成部分，可以帮助我们分清句子结构，辩明不同的语气，确切理解词语的性质和文章的意义，是公文语言的重要辅助工具。 一、标题中标点符号的用法 公文的标题，即一级标题的末尾，一般不加标点符号。例如：关于我县对《省市共建大西安意见》的几点建议，后面就不用标点符号。公文标题的内部，除用书名号和引号外，尽量不用标点符号。例如：关于对《咸阳市被征地农民就业培训和社会养老保险试行办法（征求意见稿）》的几点建议。正如有些书名号在标题中必须使用一样，有时引号也是不得不用的。例1：关于召开全县迎“双节”暨旅游工作会议的通知。例2：在全县“四防”工作会议上的讲话。例3：在推进迎接党的十八大消防安保工作暨“人人参与消防?共创平安和谐”启动仪式上的讲话。例4：关于实施“森林围城”计划的报告。“双节”、“四防”都有特定的内涵，是工作称谓的高度概括，属于特指，必须加注引号，以起到强调、提示的作用；“人人参与消防?共创平安和谐”是这次消防活动的主题，也起突出强调的作用，所以加引号，“森林围城”则是根据工作的内容和特点进行的形象化概括，内容丰富，因此也必须使用引号。与此类似的情况也并不少见，比如“863”计划、“三?八”妇女节、“9?8”投洽会、“一控双达标”、“双增双提”、“两个确保”等等。使用引号的原因一般是为了对一个特殊的概念或缩略语进行标注，以使读者明白这个词语具有特殊意义。但是，在公文标题中使用引号也要慎重，因为引号在标题中要比其它标点符号更显眼，如果可能，还是以尽量少用或不用为宜。例如：标题“构筑绿色屏障建设美丽彬县”。 公文内容里面的标题，即二、三级标题的末尾，如果是居中标题，一般也不加标点符号。例如下面三个二级标题：“过去五年工作回顾”、“今后五年奋斗目
常用标点符号及文章序号用法简表
关于常用序号的几点说明 一、结构层次序数 第一层为“一、二、三、”，第二层为“（一）（二）（三）”，第三层为“1.2.3.”第四层为“（1）（2）（3）”第五层为“①②③”。 二、文字材料中序号标点的正确使用 （一）“第一”、“第二”、“首先”、“其次”等后面应用逗号“，”。 （二）“一”、“二”、“三”等后面应用顿号“、”。 （三）“1”、“2”、“3”和“A”、“B”、“C”等后面应用齐线墨点（“.”），而不用顿号（“、”）或其它。 （四）序号如加括号，如（一）（二）（三），（1）（2）（3）等后面不加标点符号。 三、年份的正确书写 年份如用“二○○八年四月五日”的方式表述，则中间的“○”不能写成阿拉伯数字“O”或英语全角字符“o”。 四、汉语拼音的正确使用 （一）大小写：句子的首字母大写；诗行的首字母大写；专有名词每个词首字母大字；标题可以全部大写。 （二）分连写：词内连写，词间分写。 五、正确区分连接号和破折号 （一）凡文中使用连接号的应使用“～”，而不使用“——”或者“―”。 如：2008年3月～4月中的“～”，而不使用“——”或者“―”。 （二）凡文中使用破折号的应使用占两个空格的“——”而不用“～”或只占一个空格的“―”。如：再接再厉，推进语言文字规范化工作——2004年语言文字工作总结。 常用标点符号用法简表 一、基本定义 句子，前后都有停顿，并带有一定的句调，表示相对完整的意义。句子前后或中间的停顿，在口头语言中，表现出来就是时间间隔，在书面语言中，就用标点符号来表示。一般来说，汉语中的句子分以下几种： 陈述句：用来说明事实的句子。 祈使句：用来要求听话人做某件事情的句子。 疑问句：用来提出问题的句子。 感叹句：用来抒发某种强烈感情的句子。 复句、分句：意思上有密切联系的小句子组织在一起构成一个大句子。这样的大句子叫复句，复句中的每个小句子叫分句。 构成句子的语言单位是词语，即词和短语（词组）。词即最小的能独立运用的语言单位。短语，即由两个或两个以上的词按一定的语法规则组成的表达一定意义的语言单位，也叫词组。 标点符号是书面语言的有机组成部分，是书面语言不可缺少的辅助工具。它帮助人们确切地表达思想感情和理解书面语言。 二、用法简表 名称
时间前面in,on at的区别
时间前面加的介词in，at，on的区别 【in】我是“大姐”，因为我后面所接的都是较长时间。 具体用法有：1．表示在较长的时间里（如周／月份／季节／年份／世纪等）。如：in a week；in May；in spring／summer／autumn／winter；in 2008；in the 1990’s等。 2．表示在上午、下午或晚上。如：in the morning／afternoon／evening。 3．in the daytime（在白天）属于固定搭配，指从日出到日落这一段时间4．“in ＋一段时间”表示“多久以后／以内”，常与将来时连用。如：in half an hour；in ten minutes；in a few days等。 【on】我是“二姐”，我后面所接的时间多与日期有关。 具体用法有：1．表示在具体的某一天（如日期、生日、节日或星期几）。如：on May 4th，1919；on Monday；on Teachers’ Day；on my birthday；on that day等。 2．表示某一天的上午、下午或晚上。如：on the morning of July 2；on Sunday afternoon；on a cold winter evening等。 【at】我是“小妹”，因为接在我后面的时间最短。 具体用法有：1．表示在某一具体时刻，即几点几分。如：at six o’clock；at half past nine；at a quarter to six；at this time等。 2．表示在某一短暂的时间。可指某个节日或被认为是一年中标志大事的日子如：at noon；at this moment；at the end of a year；at the start of the concert，at New Year, at Christmas等。 练习： ( ) 1. Children get gifts ____ Christmas and ____ their birthdays. A. on; on B. at; on C. in; in D. in; on ( ) is nothing ____tomorrow afternoon, is there -----No. We can have a game of table tennis.
时间介词_at_in_on_用法及练习
时间介词(at, in ,on) 的用法与练习 【时间介词记法口诀】: at用在时刻前，亦与正午、午夜连， 黎明、终止和开端，at与之紧接着相伴。 周月季年长时间，in须放在其前面， 泛指一晌和傍晚，也要放在in后边。 on指特定某一天，日期、星期和节日前 某天上下和夜晚，依然要在on后站。 今明昨天前后天，上下这那每之前， at、in、on都不用，此乃习惯记心间。 1. at+night/noon/dawn/daybreak/点钟（所指的时间小于天）： at night( ) at noon( ) at down( ) at daybreak( ) at7:30( ) at 7o’clock ( ) 2. in+年/月/季节/泛指某一天的上morning，下afternoon，晚evening（所指时间大于天）： in 2004（）in March（）in spring（） in the morning（）in the evening （）in the afternoon（） 扩展：在一段时间之后。一般情况下，用于将来时，意为“在……以后”。如：He will come in two hours. 3. on+星期/日期/节日/特指某一天的上，下，晚（所指时间是天）： on Sunday（）on May 4th( )on Sunday morning( ) on Christmas Day( )/on Teachers’ Day( ) on the morning of Sunday( ) on a cold winter morning( ) 扩展：准时，按时。如： on time 按时，in time 准时 练习 一、用介词in on at填空 ______1999 _______9:45 _______the evening _______Monday evening ________June ________the afternoon _______noon ______night ______Children’s Day