摘要:

We report on a recent experiment searching for right-handed currents in the118Sbnuclear &bgr;-decay. The correlation between the spin polarization and the &bgr;-emission asymmetry of the positrons from the118Sbdecay is sensitive to the helicity structure of the weak interaction. A precision measurement of this correlation improves the limit on right-handed currents in &bgr;-decay. ©2000 American Institute of Physics.

ISSN:0094-243X    

DOI:10.1063/1.1345399

出版商:AIP    

年代:1900

数据来源: AIP

摘要:

The experiment described here will search for deviations from the V-A structure of the standard electroweak model. It is based on measuring the recoil energy spectrum in nuclear beta decay which is determined by the electron-neutrino angular correlation. For pure Fermi decays this is exactly known in the standard model and any deviation will point to additional scalar interaction. The experiment consists of a Penning trap coupled to a retardation spectrometer to measure the energy of the recoiling daughter nuclei. The current status will be presented. ©2000 American Institute of Physics.

ISSN:0094-243X    

DOI:10.1063/1.1345400

出版商:AIP    

年代:1900

数据来源: AIP

摘要:

Transition rates for coherent muon-electron conversion in the field of a nucleus (muonic atoms),&mgr;N→eN,are computed for various possible muon-number violating amplitudes. Attention is paid to relativistic atomic effects, Coulomb wave-function distortions, finite nuclear size, and nucleon distributions. ©2000 American Institute of Physics.

ISSN:0094-243X    

DOI:10.1063/1.1345401

出版商:AIP    

年代:1900

数据来源: AIP

摘要:

Many extensions of the standard model predict muon to electron conversion in the process&mgr;+Nucleus→e+Nucleusat ratios, R, of10−14to10−17muon captures. A long history of experiments which have improved upper limits on R, to the current value of<6.1×10−13set by SINDRUM II, have been limited by muon statistics rather than background. A new experiment, MECO, has been proposed to search for muon to electron conversion at levels below5×10−17.MECO takes advantage of a pulsed, high-flux muon beam produced when a proton beam at the Brookhaven AGS is incident on a target in a graded solenoidal field. The detector has 800 KeV momentum resolution and is designed to minimize the background from the beam and maximize efficiency for signal electrons. With1011stopped muons per second,R=10−16would give 5 detected events in a year of running with less than 0.5 background events expected. ©2000 American Institute of Physics.

ISSN:0094-243X    

DOI:10.1063/1.1345402

出版商:AIP    

年代:1900

数据来源: AIP

摘要:

Theoretical predictions and recent experimental searches for lepton flavor violating decays of &tgr; andB0are reviewed. So far, no evidence for such processes has been found. Up-to-date experimental upper limits on these branching fractions constrain the parameter space of some models. ©2000 American Institute of Physics.

ISSN:0094-243X    

DOI:10.1063/1.1345403

出版商:AIP    

年代:1900

数据来源: AIP

摘要:

The first measurement of direct CP violation parameterRe(&egr;′/&egr;)from the KTeV experiment is presented in this paper. Using a subset of data collected in 1996 and in 1997 we find thatRe(&egr;′/&egr;)=[28.0±3.0(stat)±2.8(syst)]×10−4.©2000 American Institute of Physics.

ISSN:0094-243X    

DOI:10.1063/1.1345404

出版商:AIP    

年代:1900

数据来源: AIP

摘要:

The NA48 experiment at CERN detects concurrently the four decay modes of the long and short lived neutral kaons. During 1998 data taking, statistics in each mode was increased by at least a factor two, with respect to the 1997 published data. A new measurement of the double ratio of the four modes has been obtained from these data. The new preliminary result on the direct CP violation parameterRe(&Vegr;′/&Vegr;)is(12.2±4.9)×10−4which, combined with the NA48 published result givesRe(&Vegr;′/&Vegr;)=(14.0±4.3)×10−4.©2000 American Institute of Physics.

ISSN:0094-243X    

DOI:10.1063/1.1345405

出版商:AIP    

年代:1900

数据来源: AIP

摘要:

Using its unique capability of strangeness tagging atK0production inpp¯→K∓&pgr;±K0(K¯0)and at decay with the lepton charge in semileptonic decays CPLEAR measured the semileptonic decay-rate asymmetryR(K¯0→e+&pgr;−&ngr;)−R(K0→e−&pgr;+&ngr;¯)R(K¯0→e+&pgr;−&ngr;)+R(K0→e−&pgr;+&ngr;¯).The asymmetry, fitted over the eigentime interval 1–20&tgr;S,yielded a non-zero result of(6.6±1.3stat±1.1syst)×10−3.A thorough phenomenological anaylsis identifies T violation inK0mixing and/or CPT violation in semileptonic decays as possible interpretations. A confrontation with world data on neutral kaon decays, however, excludes the latter with sufficient precision to establish the result as the first direct observation of time reversal non-invariance. ©2000 American Institute of Physics.

ISSN:0094-243X    

DOI:10.1063/1.1345406

出版商:AIP    

年代:1900

数据来源: AIP

摘要:

The experimental measurement ofK+→&pgr;+&ngr;&ngr;¯is reviewed. New results from experiment E787 at BNL are presented: with data from 1995–97 the branching ratio has been measured to beB(K+→&pgr;+&ngr;&ngr;¯)=(1.5−1.2+3.4)×10−10.The future prospects for additional data in this mode are examined. ©2000 American Institute of Physics.

ISSN:0094-243X    

DOI:10.1063/1.1345407

出版商:AIP    

年代:1900

数据来源: AIP

摘要:

In the standard model (SM) of electroweak interactions the positron from the decay of polarized positive muons is mainly longitudinal polarized. However the model also predicts a small transverse polarization componentPT1,which lies in the plane spanned by muon-spin and positron momentum. Interference with additional scalar couplings, as they appear in supersymmetric extensions of the SM, would result in substantial values forPT1as well as in a non zero value of the transverse componentPT2which is perpendicular to the above mentioned plane. A non zero componentPT2,proportional to the imaginary part of a possible scalar coupling, would be the first observation of time reversal violation in a purely leptonic decay. MeasuringPT1,which is proportional to the real part, amounts to a model independent determination of the Fermi coupling constant. The&mgr;PTexperiment at the Paul Scherrer Institute will improve the current experimental limitsPT1=(16±22)⋅10−3,PT2=(7±23)⋅10−3by almost one order of magnitude. Besides a description of the experiment detailed results from the last run in August 1999 will be given. ©2000 American Institute of Physics.

ISSN:0094-243X    

DOI:10.1063/1.1345408

出版商:AIP    

年代:1900

数据来源: AIP