42 research outputs found
Measurements of Direct CP Violation, CPT Symmetry, and Other Parameters in the Neutral Kaon System
We present a series of measurements based on K -> pi+pi- and K -> pi0pi0
decays collected in 1996-1997 by the KTeV experiment (E832) at Fermilab. We
compare these four K -> pipi decay rates to measure the direct CP violation
parameter Re(e'/e) = (20.7 +- 2.8) x 10^-4. We also test CPT symmetry by
measuring the relative phase between the CP violating and CP conserving decay
amplitudes for K->pi+pi- (phi+-) and for K -> pi0pi0 (phi00). We find the
difference between the relative phases to be Delta-phi = phi00 - phi+- = (+0.39
+- 0.50) degrees and the deviation of phi+- from the superweak phase to be
phi+- - phi_SW =(+0.61 +- 1.19) degrees; both results are consistent with CPT
symmetry. In addition, we present new measurements of the KL-KS mass difference
and KS lifetime: Delta-m = (5261 +- 15) x 10^6 hbar/s and tauS = (89.65 +-
0.07) x 10^-12 s.Comment: Submitted to Phys. Rev. D, August 6, 2002; 37 pages, 32 figure
Proton irradiation of CVD diamond detectors for high-luminosity experiments at the LHC
CVD diamond shows promising properties for use as a position sensitive detector for experiments in the highest radiation areas at the Large Hadron Collider. In order to study the radiation hardn ess of diamond we exposed CVD diamond detector samples to 24~GeV/ and 500~MeV protons up to a fluence of . We measured the charge collection distance, the ave rage distance electron hole pairs move apart in an external electric field, and leakage currents before, during, and after irradiation. The charge collection distance remains unchanged up to and decreases by 40~\% at . Leakage currents of diamond samples were below 1~pA before and after irradiation. The particle indu ced currents during irradiation correlate well with the proton flux. In contrast to diamond, a silicon diode, which was irradiated for comparison, shows the known large increase in leakage curren t. We conclude that CVD diamond detectors are radiation hard to 24~GeV/ and 500~MeV protons up to at least without signal loss
Measurements Of The Decay Kl → E+e-μ+μ-
Several 132 KL → e+e- μ+ μ- events were observed from the 1997 and 1999 runs of the KTeV experiments, with an estimated background of 0.8 events. In the first measurement of the parameter α using this decay mode, it was found that α=-1.59±0.37. No evidence was found for CP-violating contributions to the KLγ*γ* interaction.9014141801/1141801/5Wolfenstein, L., (1983) Phys. Rev. Lett., 51, p. 1945Belanger, G., Geng, C.Q., (1991) Phys. Rev. D, 43, p. 140Buras, A.J., Fleischer, R., (1998) Advanced Ser. Direct. High Energy Phys., 15, p. 65Uy, Z.E.S., (1991) Phys. Rev. D, 43, p. 802D'Ambrosio, G., Isidori, G., Portolès, J., (1998) Phys. Lett. B, 423, p. 385Alavi-Harati, A., (2001) Phys. Rev. Lett., 87, p. 71801. , KTeV CollaborationAlavi-Harati, A., (2001) Phys. Rev. Lett., 86, p. 5425. , KTeV CollaborationUy, Z.E.S., (2002) Eur. Phys. J. C, 23, p. 113Alavi-Harati, A., (2001) Phys. Rev. Lett., 87, p. 111802. , KTeV CollaborationHamm, J.C., (2002), Ph.D. thesis, The University of Arizona(Fermilab Report No. fERMILAB-THESIS-2002-09)Alavi-Harati, A., (1999) Phys. Rev. Lett., 83, p. 922. , KTeV CollaborationAlavi-Harati, A., (2000) Phys. Rev. D, 61, p. 072006. , KTeV CollaborationBrown, C., (1996) Nucl. Instrum. Methods Phys. Res., Sect. A, 369, p. 248Quinn, G.B., (2000), Ph.D. thesis, The University of ChicagoBarker, A.R., Huang, H., Toale, P.A., Engle, J., hep-ph/0210174Bergström, L., Massó, E., Singer, P., (1983) Phys. Lett., 131 B, p. 229Fanti, V., (1999) Phys. Lett. B, 458, p. 553. , NA48 Collaboratio
Search for chargino-neutralino production in ppbar collisions at sqrt(s) = 1.96 TeV
We present the results of a search for associated production of the chargino
and neutralino supersymmetric particles using up to 1.1 fb-1 of integrated
luminosity collected by the CDF II experiment at the Tevatron ppbar collider at
a center-of-mass energy of 1.96 TeV. The search is conducted by analyzing
events with a large transverse momentum imbalance and either three charged
leptons or two charged leptons of the same electric charge. The numbers of
observed events are found to be consistent with standard model expectations.
Upper limits on the production cross section are derived in different
theoretical models. In one of these models a lower limit on the mass of the
chargino is set at 129 GeV/c^2 at the 95% confidence level.Comment: To be submitted to Phys.Rev.Let
Measurement of the W+W- Production Cross Section in ppbar Collisions at sqrt(s)=1.96 TeV using Dilepton Events
We present a measurement of the W+W- production cross section using 184/pb of
ppbar collisions at a center-of-mass energy of 1.96 TeV collected with the
Collider Detector at Fermilab. Using the dilepton decay channel W+W- ->
l+l-vvbar, where the charged leptons can be either electrons or muons, we find
17 candidate events compared to an expected background of 5.0+2.2-0.8 events.
The resulting W+W- production cross section measurement of sigma(ppbar -> W+W-)
= 14.6 +5.8 -5.1 (stat) +1.8 -3.0 (syst) +-0.9 (lum) pb agrees well with the
Standard Model expectation.Comment: 8 pages, 2 figures, 2 tables. To be submitted to Physical Review
Letter
Crystal collimation studies at the Tevatron (T-980)
Bent-crystal channeling is a technique with a potential to increase beam-halo collimation efficiency in high-energy colliders. First measurements at the Tevatron in 2005 have shown that using a thin silicon crystal to deflect the 1-TeV proton beam halo onto a secondary collimator improves the system performance by reducing the machine impedance, beam losses in the collider detectors and irradiation of the superconducting magnets, all in agreement with simulations. Recent results, obtained with an improved goniometer and enhanced beam diagnostics, are reported here for dedicated beam studies and first full collider stores along with simulation results and plans for substantial enhancement of the T-980 experimental setup