摘要:

We present a brief theoretical overview of rare kaon decays both in and beyond the Standard Model. The Standard Model contributions to K+ → &pgr;+&ngr;&ngr;, KL → &pgr;0&ngr;&ngr;, and KL → &pgr;0ee are analyzed in detail, followed by a discussion of alternative theoretical frameworks that could modify the Standard Model predictions. Special attention is paid to ‘‘direct’’ supersymmetric flavor‐changing neutral currents induced by renormalization‐group scaling in minimal and in non‐minimal supersymmetry. We emphasize the importance of rare decays as a sensitive probe of physics beyond the Standard Model.

ISSN:0094-243X    

DOI:10.1063/1.42630

出版商:AIP    

年代:1992

数据来源: AIP

摘要:

We have developed some general ways of studying nonleptonic decays and CP‐nonvariance: the Quark Diagram Scheme, which has been very useful in making predictions, and in analyzing data and model‐calculations. For the quark‐mixing matrix of Cabibbo‐Kobayashi‐Maskawa (CKM), we have constructed, inspired by the Wolfenstein parametrization and taking full advantage of the theoretical and experimental situation, a suitable parametrization which (partly coincides with Maiani’s) is now adopted by the Particle Data Book; we also found the universal decay‐amplitude CP‐noninvariance factorXCPand introduced the use of the unitary triangles of the CKM matrix, which are now the standard language in analyzing CP‐noninvariance and nonleptonic weak decays.

ISSN:0094-243X    

DOI:10.1063/1.42629

出版商:AIP    

年代:1992

数据来源: AIP

摘要:

A discussion of the inclusive decaysB → Xs&ggr; andB → Xse+e−is given (Xsis a strange hadron), along with possible exclusive decay results from application of the Isgur‐Wise symmetry. The leading logarithmic strong interaction corrections are included. Decay rates forB → Xs&ggr; include those predictions from the minimal standard model, the standard model with two Higgs doublets, and the minimal supersymmetric model. Decay rates forB → Xse+e−are reviewed in the standard model and the two Higgs doublet model.

ISSN:0094-243X    

DOI:10.1063/1.42631

出版商:AIP    

年代:1992

数据来源: AIP

摘要:

The resonance &Ugr;(4S) decays mainly intoBmesons. However, CLEO and ARGUS have observedJ/&psgr; events from the &Ugr;(4S) with momenta greater than are allowed kinematically fromBdecay. Also, CUSB has ruled out the presence of monoenergetic photons predicted in two recent theoretical models which tried to explain this anomaly. I review the present status and propose a new scenario concerning the cause of this anomaly.

ISSN:0094-243X    

DOI:10.1063/1.42632

出版商:AIP    

年代:1992

数据来源: AIP

摘要:

We discuss recent QCD estimates of the leptonic decay constants of heavy pseudoscalar mesons. We compare the results obtained from different nonperturbative approaches, and emphasize their relevance to the physics at charm and beauty factories.

ISSN:0094-243X    

DOI:10.1063/1.42633

出版商:AIP    

年代:1992

数据来源: AIP

摘要:

We have performed a search for the rare kaon decayKL → &mgr;eat Brookhaven. Finding no events, we set a limit ofB(KL → &mgr;e)<8.4×10−11(90% confidence level) with a 5% systematic uncertainty. This is a significant improvement over previous results. In addition, we measured the branching ratio ofKL → &mgr;&mgr;; after finding 284 of these events, we calculate a branching ratio ofB(KL → &mgr;&mgr;)=(7.6±0.5±0.4)×10−9.

ISSN:0094-243X    

DOI:10.1063/1.42634

出版商:AIP    

年代:1992

数据来源: AIP

摘要:

E771 is a Fermilab fixed target open geometry high acceptance spectrometer experiment to study production of beauty states in 0.8 TeV proton‐nucleus interactions, and beauty decay particularly to final states containing a J/&PSgr; (detected via its decay to &mgr;+&mgr;−). The spectrometer consists of a silicon microstrip vertex detector (final configuration, 24 planes; x, y, u, v; of 25 and 50 micron pitch), upstream of which are beam‐defining planes of silicon microstrip detectors and target foils of various materials and thicknesses; the SVD is followed by tracking planes of drift‐ and proportional‐wire‐chambers, a momentum‐analysing bending magnet, further planes of DC’s, PWC’s and pad chambers, a &ggr;‐ and electron‐detecting lead glass wall, and finally several meters of iron interspersed with muon‐detecting resistive pad chambers and scintillators. Progress is reviewed in building, installing and tuning the equipment for the next Fermilab fixed target run beginning in mid‐1991, and expected to continue for 5 months. An extensive data run is anticipated for the 1993–4 fixed target period. In the 1991 run several dozen fully‐ reconstructed B to J/&PSgr; to &mgr;=&mgr;−events should be obtained per month of good running at an interaction rate of 2 MHz. For future runs the goal is to operate at 10 MHz and to reconstruct several thousand B decays per year to measure B decay branching ratios, study B0B¯0mixing, and search for CP violation effects.

ISSN:0094-243X    

DOI:10.1063/1.42635

出版商:AIP    

年代:1992

数据来源: AIP

摘要:

We impose new limits on flavor changing neutral currents (fcnc) applied to the 4×4 mixing matrix of the next heaviest down quark in a model with extraSU(2)Lsinglet down quarks, such as inE6. We find the new bounds still allow tree levelZexchange to dominateBd0−B¯d0mixing, but notBs0−B¯s0mixing. The unitarity ‘‘triangle’’ may still have added a detectable fourth side. TheCPasymmetries fromBd0may show a newCPviolating phase or the usual CKM phase.

ISSN:0094-243X    

DOI:10.1063/1.42636

出版商:AIP    

年代:1992

数据来源: AIP

摘要:

We give an update on the current search for tree level Flavor Changing Weak Neutral Current (FCWNC) processes, emphasizing the recent search for B→&mgr;+&mgr;−X in the UA1 experiment. We discuss techniques to extend the search for FCWNC. We also report on the current states of B0−B¯0(Bd0, Bs0) mixing. Using the world data it can now be shown that &khgr;s=0.5±0.2. We show that the dominant component of the B−B¯ mixing may not be due to tree level FCWNC.

ISSN:0094-243X    

DOI:10.1063/1.42637

出版商:AIP    

年代:1992

数据来源: AIP

摘要:

We review recent theoretical estimates, relevant to the branching ratio of theb→sexclusive transitionB→K*&ggr;. These include the hadronic couplings of the short‐distance effective Hamiltonian, the long‐distance effects and some backgrounds in the search for this decay in high energy experiments, such as at LEP.

ISSN:0094-243X    

DOI:10.1063/1.42638

出版商:AIP    

年代:1992

数据来源: AIP