首页 | 本学科首页   官方微博 | 高级检索  
相似文献
 共查询到20条相似文献,搜索用时 500 毫秒
1.
Using the ARGUS detector at thee + e storage ring DORIS II, flavour-dependent kaon production inB meson decays has been studied. Using the leptons as flavour tags, it has been possible to separately measure the multiplicities ofK +,K andK s 0 in inclusiveB decays and in semileptonicB decays. The kaon production in semileptonicB decays was further used to estimate the ratio of charmed decays over all decays, and thus also the fraction of charmlessB decays.DESY, IfH Zeuthen  相似文献   

2.
A large CP-violating phase uncovered recently by CDF and DØ Collaborations in the time-dependent CP asymmetry (CPA) of the BsJ/Ψ decay clearly indicates that a non-Cabibbo–Kobayashi–Maskawa (CKM) phase has to be brought into the bs transition. We find that the model with SU(2)L singlet exotic quarks cannot only provide the new phase induced from the Z-mediated flavor changing neutral current (FCNC) at tree level, but also strongly relate the Bs mixing, BqVq+ (Vd[s]=K*[]) and Bsμ+μ together. In particular, we show that the new CP phase can be unambiguously exposed by the large statistical significances of T violating observables in BqVq+, while the branching ratio of Bsμ+μ can be enhanced to be O(10−8).  相似文献   

3.
Several years ago, it was pointed out that the U-spin-related decays Bd→π+π-, Bs→K+K- and Bd→πK±, Bs→π±K offer interesting strategies for the extraction of the angle γ of the unitarity triangle. Using the first results from the Tevatron on the Bs decays and the B-factory data on Bu,d modes, we compare the determinations of γ from both strategies, study the sensitivity on U-spin-breaking effects, discuss the resolution of discrete ambiguities, predict observables that were not yet measured but will be accessible at LHCb, explore the extraction of the width difference ΔΓs from untagged Bs→K+K- rates, and address the impact of new physics. The data for the Bd→π+π-, Bs→K+K- system favour the BaBar measurement of direct CP violation in Bd→π+π-, which will be used in the numerical analysis and result in a fortunate situation, yielding γ=(66.6+4.3+4.0 -5.0-3.0)°, where the latter errors correspond to a generous estimate of U-spin-breaking effects. On the other hand, the Bd→πK±, Bs→π±K analysis leaves us with 26°≤γ≤70°, and points to a value of the Bs→π±K branching ratio that is larger than the current Tevatron result. An important further step will be the measurement of mixing-induced CP violation in Bs→K+K-, which will also allow us to extract the B0 s–B̄0 s mixing phase unambiguously with the help of Bs→J/ψφ at the LHC. Finally, the measurement of direct CP violation in Bs→K+K- will make the full exploitation of the physics potential of the Bs,d→ππ,πK,KK modes possible.  相似文献   

4.
Flavor symmetry and symmetry breaking, K0– mixing and possible effects of new physics on CP violation in weak decay modes D±KS,L+X±, (KS,L0)K*+X± (for X=π,ρ,a1) and D±sKS,L+X±s, (KS,L0)K*+X±s (for Xs=K,K*) are analyzed. Relations between D± and D±s decay branching ratios are obtained from the ds subgroup of SU(3) and dominant symmetry-breaking mechanisms are investigated. A CP asymmetry of magnitude 3.3×10−3 is shown to result in the standard model from K0– mixing in the final-state. New physics affecting the doubly Cabibbo-suppressed channels might either cancel this asymmetry or enhance it up to the percent level. A comparison between the CP asymmetries in D±(s)KSX±(s) and D±(s)KLX±(s) can pin down effects of new physics.  相似文献   

5.
It is well known that the study of flavour physics and CP violation is very important to critically test the Standard Model and to look for possible signature of new physics beyond it. The observation of CP violation in kaon system in 1964 has ignited a lot of experimental and theoretical efforts to understand its origin and to look for CP violation effects in other systems besides the neutral kaons. The two B-factories BABAR and BELLE, along with other experiments, in the last decade or so made studies in flavour physics and CP violation a very interesting one. In this article we discuss the status and prospectives of the flavour physics associated with the strange, charm and bottom sectors of the Standard Model. The important results in kaon sector will be briefly discussed. Recently, mixing in the charm system has been observed, which was being pursued for quite some time without any success. The smallness of the mixing parameters in the charm system is due to the hierarchical structure of the CKM matrix. Interestingly, so far we have not found CP violation in the charm system but in the future, with more dedicated experiments at charm threshold, the situation could change. Many interesting observations have been made in the case of bottom mesons and some of them show some kind of deviations from that of the Standard Model expectations which are mainly associated with the bs flavour changing neutral current transitions. It is long believed that the B s system could be the harbinger of new physics since it is a system in which both bottom and strange quarks are the constituents. Recently, D0 and CDF announced their result for the B s mixing which is claimed to be the first possible new physics signature in the flavour sector. We plan to touch upon all important issues pointing out both theoretical and experimental developments and future prospects in this review article.  相似文献   

6.
Based on the quark-diagram scheme and the recent measurement of D0→π0π0, we analyze the decays D0→π+π, π0π0, K+K, and . To fit the data, we find that there must be both final-state-interaction and SU(3)-breaking effects: of the former, nonzero elastic phase shifts in both π and are determined and no inelasticity in phase shifts is required; the SU(3) breaking effects are at the maximal level of 30% and of particular interest are those in the spectator W-emission and the non-spectator W-exchange diagrams.  相似文献   

7.
The CHORUS experiment is designed to search for νμ → ντ oscillation with a hybrid detector system containing 800 kg nuclear emulsions as target and vertex detector. Run I (320 000 recorded νμCC in 1994/5) and more than half of the run II (460 000 νμCC in 1996/7) data taking have been successfully completed. Approximately 80 000 events have been analyzed so far, searching for and τh (nπ0) ντ decays. No candidate has been found, leading to a limit sin2μτ ≤ 4.5 10−3 for large Δm2.  相似文献   

8.
9.
Data on at rest show two resonant processes: (a) f0(1370)η,f0(1370)→σσ and ρρ, (b) η(1440)σ, η(1440)→ηπ+π. The branching ratio BR[f0(1370)→ρρ]/BR[f0(1370)→σσ]=0.98±0.25 in the mass range available here. Using data on , the ratio Γ5 for f0(1370). The effects of the strongly s-dependent width of f0(1370) are discussed in some detail.The η(1440) is observed decaying to ησ and a0(980)π, with strong destructive interference between them. In its decay to a0(980)π, a narrow peak appears in the ηπ mass spectrum, but 30–50 MeV above that usually attributed to a0(980) and significantly above the KK threshold. This effect is explained naturally by a two-step process: η(1440)→K*(890)K followed by rescattering of the two kaons through a0(980) to ηπ above the KK threshold.  相似文献   

10.
Usually, B0π+π decays are expressed in terms of weak amplitudes explicitly dependent on the CKM weak phase α or γ. In this Letter, we show that the weak amplitudes can be rewritten such that a manifest dependence on β emerges instead. Based on this, we constrain new-physics contributions to the CP-violating phase d in mixing. Further, we apply reparametrization invariance and use QCD factorization predictions to investigate the bounds on an additional new-physics amplitude in B0π+π.  相似文献   

11.
The change asymmetry in semi-leptonic kaon decays has been measured as a function of the kaon lifetime. High statistics data of Ke30 and Kμ30 decay modes agree with each other and with the general expectation of the CP violation phenomenology together with the ΔS?ΔQ rule. The KL-KS mass difference obtained is Δm = (0.533 ± 0.004) × 1010 s?1.  相似文献   

12.
The dependence of the strangeness production on the number of nucleons involved in the annihilation process is investigated experimentally in and 4He annihilation at rest. In He, annihilations with the involvement of one and several nucleons (B=0 and B1 baryonic number, respectively) are identified. Strangeness enhancement factors, i.e., ratios of K±, , K0* and ϕ meson yields in 4He to the same yields in H, are derived for final states containing 4 charged mesons (2π+2π, π+ππK±, π+πK+K). This work completes a previous investigation concerning charged kaon production in meson final states without neutral mesons. The results are compared with our previous ones and with results found in experiments on heavy-ion collisions. It is put in evidence that the strangeness content in the energy blob created by the annihilation has a lower or higher intensity depending on the reaction channel: for instance, π+ππK± production increases with B and π+πK+K production decreases. The maximum enhancement factor (about 22) is found for π+ππK+ without neutral mesons. This value (as well as that concerning π+π+πK) is definitely higher than the values predicted by theoretical investigations based on the formation of a highly excited hadronic gas in the annihilation on few nucleons and values found in heavy-ion collisions. Is it the signature of the formation of quark–gluon plasma?  相似文献   

13.
We study CP asymmetries in rare B decays within supersymmetry with a U(2)3 flavour symmetry, motivated by the SUSY flavour and CP problems, the hierarchies in the Yukawa couplings and the absence so far of any direct evidence for SUSY. Even in the absence of flavour-blind phases, we find potentially sizable CP violating contributions to bs decay amplitudes. The effects in the mixing-induced CP asymmetries in BϕK S and BηK S , angular CP asymmetries in BK μ + μ and the direct CP asymmetry in BX s γ can be in the region to be probed by LHCb and next generation B factories. At the same time, these effects in B decays are compatible with CP violating contributions to meson mixing, including a non-standard B s mixing phase hinted by current tensions in the CKM fit mostly between SyKS, eKS_{\psi K_{S}}, \epsilon_{K} and DMBs/DMBd\Delta M_{B_{s}}/\Delta M_{B_{d}}.  相似文献   

14.
Oxalyl chloridefluoride (COCl)(COF) exhibits moderately strong discrete absorption in the 3050–3540Å region. The band spectrum has been analyzed as an allowed electronic transition of the planar trans molecule. The most active vibrations are the carbonyl stretching modes ν1′ and ν2′ and the in-plane bending mode ν9. Various other fundamental frequencies in the combining electronic states have been identified. The 000 band is at 28 724.5 cm−1; partial rotational analysis confirms that this band is type C. The appearance of “line” structure in the wings of the band is discussed and an explanation offered. The vibrational and rotational analyses confirm that the transition is under the Cs point group, as expected for a singlet-singlet n → π* type of excitation.  相似文献   

15.
In a data sample of four million hadronic Z decays collected with the ALEPH detector at LEP, four Λb baryon candidates are exclusively reconstructed in the Λb → Λc+π channel, with the Λc+ decaying into pKπ+, , or Λπ+π+π. The probability of the observed signal to be due to a background fluctuation is estimated to be 4.2 × 10−4. The mass of the Λb is measured to be 5614±21 (stat.) ± 4 (syst.) MeV/c2.  相似文献   

16.
The ultraviolet emission systems of HgI—CX, DX, F3X, GX, and HX—are photographed and analyzed using tesla-discharge sources containing isotopically pure 200Hg. The previous assignment for F3X is revised, the main change being a decrease by 3 units in the v″ numbering. Results for the other systems corroborate the existing interpretations, except that for CX there are prominent intensity gaps in the unresolved rotational structure of the bands, not reported previously for “natural” HgI spectra. These gaps are attributed to perturbations of the C state by high levels (v ≈ 90) of the B state. The data for these systems are combined with existing BX data for 200Hg127I and 200Hg129I and fitted simultaneously to yield optimal vibrational parameters for all states. In this analysis the X state is fitted to a mixed representation—a polynomial in ( ) for v ≤ 20 and a near-dissociation expansion for v ≥ 20, with Gv and its first derivative constrained to be continuous at v = 20. The revised estimate of e for X is 2800 ± 40 cm−1. The recommended vibrational parameters (cm−1) for v ≤ 20 are ωe = 125.41, ωexe = 1.009, ωeye = −0.0159.  相似文献   

17.
We study the decays Kππ in one-loop two-flavour Chiral Perturbation Theory. We provide arguments why the calculation of the coefficient of the pionic chiral logarithm M=M2logM2 is unique and then perform the calculation. As a check we perform the reduction of the known three-flavour result. Our result can be used to perform the extrapolation to the physical pion mass of direct lattice QCD calculations of Kππ at fixed ms or . The underlying arguments are expected to be valid for heavier particles and other processes as well.  相似文献   

18.
George W S Hou 《Pramana》2006,67(5):773-782
There are currently two hints for new physics involving CP violation in bs transitions: ΔSS f − S J ϕK ≠ 0, and difference in direct CP asymmetry ΔA A K+π 0A K+π ≠ 0. We explore the two scenarios with a large and unique new CP phase in bs transitions. Motivated by ΔS ≠ 0, we update on the right-handed strange-beauty squark sb 1R at TeV scale. Motivated by ΔA ≠ 0, we explore sequential fourth generation t′ and b′ quarks. Both scenarios can survive constraints such as SM level bsγ, sll and B s mixing, and predict sizable CP violation in B s mixing. The fourth generation picture predicts sizable K Lπ 0 vv. Direct search for sb R, b′ and t′ at hadronic colliders, such as Tevatron Run II and LHC, can complement further CP violation studies at these machines, as well as at the future Super B factory.  相似文献   

19.
A modified INDO (intermediate neglect of differential overlap) method is used to calculate the electronic spectra of naphthalene and some mono-, di-, and tetraazanaphthalenes. The technique is capable of reproducing the better classified bands of this series within a rms error of 1000 cm−1.The four lowest π-π* bands of naphthalene are well represented; a fifth band reported at 52,600 cm−1, and generally assigned 1B2u(π-π*), may be 1B3g(π-π*) borrowing intensity. The lowest excited singlet state calculated for quinoline is n → π*, estimated nearly degenerate with the lowest π-π*, while that for isoquinoline is calculated π-π*; experimental evidence supports the π-π* assignment in both cases, but the corresponding absorption in quinoline appears complex. Of the diazanaphthalenes examined (with two nitrogens in one benzenoid ring) all are calculated to have one n* transition before the first π-π* except phthalazine, in which two n* transitions are calculated to be the lowest lying. This is in accord with experimental evidence to date, although the nature of the observation in phthalazine is reinterpreted as one 1B2(n-π). 1,4,5,8-tetrazanaphthalene is predicted to have a group theoretically forbidden n* excited state as low as 21,000 cm−1, and should prove interesting experimentally. Even though n* excited states are often calculated to be the lowest lying, none of these compounds are predicted to have an “n” orbital as homo.Further interpretations of the spectra of the azanaphthalenes are made in view of the calculations. Theoretical limitations of the method employed for this study are discussed.  相似文献   

20.
Recently, we have seen interesting progress in the exploration of CP violation in B0 d→π+π-: the measurements of mixing-induced CP violation by the BaBar and Belle collaborations are now in good agreement with each other, whereas the picture of direct CP violation is still unclear. Using the branching ratio and direct CP asymmetry of B0 d→π-K+, this situation can be clarified. We predict , which favours the BaBar result, and we extract γ=(70.0+3.8 -4.3)°, which agrees with the unitarity triangle fits. Extending our analysis to other B→πK modes and B0 s→K+K- with the help of the SU(3) flavour symmetry and plausible dynamical assumptions, we find that all observables with colour-suppressed electroweak penguin contributions are measured to be in excellent agreement with the standard model. As far as the ratios Rc,n of the charged and neutral B→πK branching ratios are concerned, which are sizeably affected by electroweak penguin contributions, our standard-model predictions have almost unchanged central values but significantly reduced errors. Since the new data have moved quite a bit towards these results, the “B→πK puzzle” for the CP conserving quantities has been significantly reduced. However, the mixing-induced CP violation of B0 d→π0KS does look puzzling; if confirmed by future measurements, this effect could be accommodated through a modified electroweak penguin sector with a large CP violating new-physics phase. Finally, we point out that the established difference between the direct CP asymmetries of B±→π0K± and Bd→πK± appears to be generated by hadronic and not by new physics.  相似文献   

设为首页 | 免责声明 | 关于勤云 | 加入收藏

Copyright©北京勤云科技发展有限公司  京ICP备09084417号