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1.
The ellipsoidal bag model is used to describe heavy quark systems such asQ ,Q g andQ 2 . Instead of two step model, these states are described by an uniform picture. The potential derived from the ellipsoidal bag forQ is almost equivalent to the Cornell potential. For aQ 2 system with large quark pair separation, an improvement of 70 MeV is obtained comparing with the spherical bag.  相似文献   

2.
3.
We calculate CP-odd correlations inZ decays to leptons, . These correlations are sensitive to the weak dipole moment of the . With 107 producedZ particles and with observation of the decay channels and v we estimate that can be determined with an accuracy of about (1 s.d.).  相似文献   

4.
A systematic study of possible deuteronlike twomeson bound states,deusons, is presented. Previous arguments that many such bound states may exist are elaborated with detailed arguments and numerical calculations including, in particular, the tensor potential. This tensor potential which is crucial for the deuteron binding is shown to be very important also in the mesonic case. Especially, in the pseudoscalar3 P 0 pseudoscalar-vector and vector-vector channels the important observation is made that the centrifugal barrier from theP-wave can be overcome by the 1/r 2 and 1/r 3 terms of the tensor potential. In the heavy meson sector one-pion exchange alone is strong enough to form at least deuteronlike and composites bound by approximately 50 MeV. Composites of and states bound by pion exchange alone are expected near the thresholds, while in the light meson sector one generally needs some additional short range attraction to form bound states. The quantum numbers of these states areI=0, andJ PC=0–+, 1++ for the states andI=0,J PC=0++, O–+, 1+– and 2++ for the composites. In the states: b (10545), b1(10562) are predicted and in , one finds the states: b (10590), bQ (10582),h b(10608), b2(10602). Near the threshold the states: c (3870), c0(3870) are predicted, and near the threshold one finds the states: b0(4015), c (4015),h c(4015), c2(4015). Within the light meson sector pion exchange gives strong attraction for and systems with quantum numbers where the best non- candidates exist, although pion exchange alone is not strong enough to support such bound states. Thus, although one cannot conclude with certainty it to be the case, this fact does favour the picture that the (1440) and thef 1 (1420) are mainly composites and thef 0(1710) mainly a bound state, while thef 0(1515) andf 2(1520) could be predominantly composites. If the predicted and states are found, these would support this interpretation of the light states. In channels with exotic flavour orCP quantum numbers pion exchange is generally repulsive or quite weak. Therefore one does not expect that such deuteronlike bound states exist, althoughB*B* may be an exception.  相似文献   

5.
We present a detailed study of and and the subsequent decays of , , and at the LHC . We explore the relevant supersymmetry parameter range. We calculate the cross sections as well as the rates for interesting signatures such as the production of one or two leptons on the lepton side.  相似文献   

6.
It is shown that one can fit the available data on thea o(980),f o(1300) andK o * (1430) mesons as a distorted 0++ nonet using very few (5–6) parameters and an improved version of the unitarized quark model. This includes all light two-pseudoscalar thresholds, constraints from Adler zeroes, flavour symmetric couplings, unitarity and physically acceptable analyticity. The parameters include a bare or mass, an over-all coupling constant, a cutoff and a strange quark mass of 100 MeV, which is in accord with expectations from the quark model. It is found that in particular for thea 0(980) andf 0(980) the component, in the wave function is large, i.e., for a large fraction of the time the state is transformed into a virtual pair. This component, together with a similar component of for thea 0(980), and , and components for thef 0(980), causes the substantial shift to a lower mass than what is naively expected from the component alone. Mass, width and mixing parameters, including sheet and pole positions, of the four resonances are given, with a detailed pedagogical discussion of their meaning.  相似文献   

7.
In the reactione + e W + W ( ) ( ) we expect that normally the colour singlet systems ( ) and ( ) hadronize independently into two hadron chains or strings. However also the pairs ( ) and ( ) form colour singlets with probability 1/N c 2 =1/9. This probability could be further enhanced by gluon exchange. We therefore expect that the hadronization can give recoupled colour strings between these quark-antiquark pairs with some small probability, and a study of this effect will give interesting information about the vacuum structure. In this paper we discuss a possible experimental signal for recoupled events and show that such events can be identified also when the effect of gluon emission before the recoupling is taken into account.  相似文献   

8.
The cross-section for the production of quarks ine + e annihilation, that proves to be at a level of for is calculated within the frames of the QCD perturbation theory. The cross sections for the associated production of 1S-and 2S-wave states ofB c-meson in the reaction were calculated in the nonrelativistic model of a heavy quarkonium. The number of bc -hyperons to be expected at LEP is estimated on the basis of the assumption on quark-hadron duality.  相似文献   

9.
Using the ARGUS detector at thee + e storage ring DORIS II, we have studied nine decay modes of theD 0 meson. In addition to a higher-precision determination of the branching ratios for these modes, several new channels, the decays , and , have been observed for the first time.Supported in part by the Institute of Physics, University of Lund, Sweden  相似文献   

10.
An analysis of secondary hadrons fromZ 0 (91) decays of the LEP experiments indicates that the scaling of distributions implies the same temperatureT=0.261 GeV for all the secondaries. The multiplicities ofZ 0,K 0, ,..., and computed with their quark contents and the sameT agree with the data. The ratio of to the phase-space covered by the rapidity distribution, depends only on the energy, , fore + e annihilations and collisions as well.  相似文献   

11.
An extension of the Supersymmetric Standard Model to the supersymmetricSU(2) L×SU(2) R×U(1) B–L model is considered. The gauge group contains a bidoublet and triplet Higgs field. We investigate the possibility of detecting chargino and neutralino production in -collisions atCDF, namely . A numerical analysis is performed for , tan 1 and a lower bound on the lightest supersymmetric particle (LSP) mass, GeV. Using conservative assumptions ofM WR300 GeV andgg Lg R, we find the cross sections are: , and pb, and thus L 24 L at TeV. Cross sections are also given for larger values of the center of mass energy up to those available at the SSC. The results are compared with the prompt-lepton background of theW L, R decays from . Both decays for bosons show Jacobian peaks for (p T150 GeV forM WR) at =90°. Furthermore the chargino signature unlike the promptlepton background is symmetric under the Jacobian peak. We also exhibit the dependence of the angular distribution of the chargino on the c.m. angle forp T40 GeV, 150 GeV at TeV.  相似文献   

12.
There is an intriguing discrepancy between values measured directly at the CERNZ 0-factory and low-energy (at few GeV) measurements transformed toQ=M z0 by a massless QCD evolution relation. There exists and attempt to reconcile this discrepancy by introducing a light gluinog in the MSSM. We study in detail the influence of heavy thresholds on evolution. First, we construct the exact explicit solution to the mass-dependent two-loop RG equation for the running . This solution describes heavy thresholds smoothly. Second, we use this solution to recalculate a new values corresponding to low-energy input data. Our analysis demonstrates that usingmass-dependent RG procedure generally produces corrections of two types: Asymptotic correction due to effective shift of threshold position; Local threshold correction only for the case when input experiment lies in the close vicinity of heavy particle threshold:Q expt -M h . Both effects result in the effective shift of the values of the order of 10–3. However, the second one could be enhanced when the gluino mass is close to a heavy quark mass. For such a case the sum effect could be important for the discussion of the light gluino existence as it further changes theg mass.Work supported in part by INTAS-93-1180  相似文献   

13.
The forward-backward asymmetry of has been measured using approximately 2.15 million hadronicZ 0 decays collected at the LEP e+e collider with the OPAL detector. A lifetime tag technique was used to select an enriched event sample. The measurement of the asymmetry was then performed using a jet charge algorithm to determine the direction of the primary quark. Values of:
  相似文献   

14.
Within the framework of ellipsoidal bag model, the state at finite temperature is investigated, and the dependence of the energy of the system on the interquark separation is obtained. We calculate the spectrums of and statesat different temperature for TM and TE mode respectively.  相似文献   

15.
A comparative investigation of various pomeron models is carried out through the study of their predicted values of tot,B, and in high energypp and scattering. Our results strongly support a picture of the pomeron in which we have both moderate blackening and expansion of the amplitude in impact parameter space as a function of energy in the ISR-SSC domain. Our analysis shows the data is compatible with a hybrid eikonal model which combines the hard Lipatovlike QCD pomeron with the old fashioned soft pomeron and Regge terms. We show that the additive quark model, at least in the naive form, is not compatible with the data.Work supported in part by Israel Academy of Sciences and Humanities  相似文献   

16.
An analysis of the single-particle distribution of inclusive at in terms of the covariant Boltzmann factor indicates that the Feynman-Yang scaling holds, the temperature ofW being 0.188 GeV. The specific central particle density ofW is found to be the same as andK 0 production at the same energy.  相似文献   

17.
The spectrum of , Jp=0+, 2+ mesons is discussed. We have shown that due to instanton-induced forces the physical states are strong mixtures of theSU f (3) group basis states. The cross-sections for annihilation of the system into mesons are obtained. Thea 0(980) meson is considered as meson consisting of 9 f and 36 f plets. The branchings are also predicted for the cross-sections for production of thea 0(980) and tensor mesons in annihilation.  相似文献   

18.
A search for e and oscillations has been carried out with the CHARM II detector exposed to the CERN wide band neutrino beam. The data were collected over five years, alternating beams mainly composed of muon-neutrinos and muon-antineutrinos. The number of interactions of e and observed is comparable with the number of events expected from flux calculations. For large squared mass differences the upper limits obtained on the mixing angle aresin 22 < 9.4=" ·=">–3 for oscillating to e andsin 22 < 4.8=" ·=">–3 for to , at the 90% confidence level. Combining neutrino and antineutrino data the upper limit is 5.6 · 10–3.On leave of absence from ITEP (Moscow)  相似文献   

19.
In the framework of the heavy-quark effective theory, theO ( O(QCD)) corrections are estimated in the test of factorization hypothesis forB-meson nonleptonic decays proposed by Bjorken. Similar calculations are also carried out for b nonleptonic decays. The effects of these corrections on the estimate of theD s -meson decay constant are discussed.  相似文献   

20.
annihilation at rest into five pions was studied in the ASTERIX spectrometer by stopping antiprotrons from LEAR in a H2 or D2 gas target. In annihilations in H2 leading to the ++0 final state, the invariant mass spectra of two, three, and four pions show no evidence for any new narrow states. In the difference of the four pion mass spectra recoiling against a and those recoiling against a + shows a resonance-like structure ( (1480)), confirming a previous analysis with a smaller event sample. The (1480) mass is shown to depend strongly on the momentum of the spectator proton. In H2, we searched for the (1480) in the reaction (1480), (1480) ++ to clarify whether the (1480) is identical to the 4-mode of thef 2 (1520). No evidence for this decay mode was found. A prominent resonance in innihilation into five pions is the meson. We find two quasi-two-body intermediate states: and (1235). The mass and width of theb 1 (1235) are determined to be:
  相似文献   

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