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CP violation and suppressed $B_s$ decays at CDF

Description: The study of heavy-quark decays continues to have wide interest as a possible avenue for the discovery of physics beyond the standard model. With data samples as large as 6 fb{sup -1}, the CDF collaboration is exploring new channels that will extend the reach of measurements in probing the CKM mechanism of CP violation. Several new measurements are presented.
Date: December 1, 2011
Creator: Lewis, J. D.
Partner: UNT Libraries Government Documents Department

Observation of the Semileptonic Decays B to D*taunu and Evidence for B to D tau nu

Description: We present measurements of the semileptonic decays B{sup -} {yields} D{sup 0}{tau}{sup -}{bar {nu}}{sub {tau}}, B{sup -} {yields} D{sup *0}{tau}{sup -}{bar {nu}}{sub {tau}}, B{sup -} {yields} D{sup +}{tau}{sup -}{bar {nu}}{sub {tau}}, and B{sup -} {yields} D{sup *+}{tau}{sup -}{bar {nu}}{sub {tau}}, which are potentially sensitive to non-Standard Model amplitudes, The data sample comprises 232 x 10{sup 6} {Upsilon}(4s) {yields} B{bar B} decays collected with the BABAR detector. From a combined fit to B{sup -} and {bar B}{sup 0} channels, we obtain the branching fractions {beta}(B {yields} D{sub {tau}}{sup -}{bar {nu}}{sub {tau}}) = (0:86 {+-} 0:24 {+-} 0:11 {+-} 0:06)% and {beta}(B {yields} D*{tau}{sup -}{bar {nu}}{sub {tau}}) = (1:62 {+-} 0:31 {+-} 0:10 {+-} 0:05)% (normalized for the {bar B}{sup 0}), , where the uncertainties are statistical, systematic, and normalization-mode-related.
Date: September 14, 2007
Creator: B., Aubert
Partner: UNT Libraries Government Documents Department

Direct CP, Lepton Flavor and Isospin Asymmetries in the Decays B->K(*)l+l-

Description: We measure rate asymmetries for the rare decays B {yields} K{sup (*)}{ell}{sup +}{ell}{sup -}, where {ell}{sup +}{ell}{sup -} is either e{sup +}e{sup -} or {mu}{sup +}{mu}{sup -}, using a sample of 384 million B{bar B} events collected with the BABAR detector at the PEP-II e{sup +}e{sup -} collider. We find no evidence for direct CP or lepton-flavor asymmetries. For dilepton masses below the J/{psi} resonance, we find evidence for unexpectedly large isospin asymmetries in both B {yields} K{ell}{sup +}{ell}{sup -} and B {yields} K*{ell}{sup +}{ell}{sup -} which differ respectively by 3.2{sigma} and 2.7{sigma}, including systematic uncertainties, from the Standard Model expectations.
Date: March 3, 2009
Creator: Aubert, B.; Bona, M.; Karyotakis, Y.; Lees, J.P.; Poireau, V.; Prencipe, E. et al.
Partner: UNT Libraries Government Documents Department

Diboson physics at CDF

Description: We have studied diboson events produced by p{bar p} collisions at {radical}s = 1.96 TeV using the CDF detector. Our observations of Z{gamma}, WZ, and ZZ production are consistent with Standard Model predictions, and we set limits on some anomalous couplings.
Date: July 1, 2008
Creator: Phillips, Thomas J.
Partner: UNT Libraries Government Documents Department

Measurement of the forward-backward charge asymmetry and extraction of $sin^2Theta^{eff}_W$ in $p\bar{p} \to Z/\gamma^{*}+X \to e^+e^-+X$ events produced at $\sqrt{s}=1.96$ TeV

Description: We present a measurement of the forward-backward charge asymmetry (A{sub FB}) in p{bar p} {yields} Z/{gamma}* + X {yields} e{sup +}e{sup -} + X events at a center-of-mass energy of 1.96 TeV using 1.1 fb{sup -1} of data collected with the D0 detector at the Fermilab Tevatron collider. A{sub FB} is measured as a function of the invariant mass of the electron-positron pair, and found to be consistent with the standard model prediction. We use the A{sub FB} measurement to extract the effective weak mixing angle sin{sup 2} {theta}{sub W}{sup eff} = 0.2327 {+-} 0.0018 (stat.) {+-} 0.0006 (syst.).
Date: April 1, 2008
Creator: Abazov, V.M.; /Dubna, JINR; Abbott, B.; U., /Oklahoma; Abolins, M.; U., /Michigan State et al.
Partner: UNT Libraries Government Documents Department

Search for CP Violation in the Decays D0 to K- K+and D0 to pi- pi+

Description: We measure CP-violating asymmetries of neutral charmed mesons in the modes D{sup 0} {yields} K{sup -}K{sup +} and D{sup 0} {yields} {pi}{sup -}{pi}{sup +} with the highest precision to date by using D{sup 0} {yields} K{sup -}{pi}{sup +} decays to correct detector asymmetries. An analysis of 385.8 fb{sup -}1 of data collected with the BaBar detector yields values of a{sup KK}{sub CP} = (0.00 {+-} 0.34 (stat.) {+-} 0.13 (syst.))% and a{sup {pi}{pi}}{sub CP} = (-0.24 {+-} 0.52 (stat.) {+-} 0.22 (syst.))%, which agree with Standard Model predictions.
Date: September 24, 2007
Creator: Aubert, B.; Bona, M.; Boutigny, D.; Karyotakis, Y.; Lees, J.P.; Poireau, V. et al.
Partner: UNT Libraries Government Documents Department

Study of direct CP violation in B+- ---> J/psi K+- (pi+-) file decays

Description: The authors present a search for direct CP violation in B{sup {+-}} {yields} J/{psi}K{sup {+-}}{pi}{sup {+-}} decays. The event sample is selected from 2.8 fb{sup -1} of p{bar p} collisions recorded by D0 experiment in Run II of the Fermilab Tevatron Collider. The charge asymmetry A{sub CP}(B{sup +} {yields} J/{psi}K{sup +}) = +0.0075 {+-} 0.0061(stat.) {+-} 0.0027(syst.) is obtained using a sample of approximately 40 thousand B{sup {+-}} {yields} J/{psi}K{sup {+-}} decays. The achieved precision is of the same level as the expected deviation predicted by some extensions of the standard model. They also measured the charge asymmetry A{sub CP}(B{sup +} {yields} J/{psi}{pi}{sup +}) = -0.09 {+-} 0.08(stat.){+-}0.03(syst.).
Date: February 1, 2008
Creator: Abazov, V.M.; /Dubna, JINR; Abbott, B.; U., /Oklahoma; Abolins, M.; U., /Michigan State et al.
Partner: UNT Libraries Government Documents Department

A Search for B -> tau nu Recoiling Against B- -> D0 l- nu X

Description: The authors present a search for the decay B{sup +} {yields} {ell}{sup +}{nu}{sub {ell}} ({ell} = {tau}, {mu}, or e) in (458.9 {+-} 5.1) x 10{sup 6} B{bar B} pairs recorded with the BABAR detector at the PEP-II B-Factory. They search for these B decays in a sample of B{sup +}B{sup -} events where one B-meson is reconstructed as B{sup -} {yields} D{sup 0}{ell}{sup -}{bar {nu}}X. Using the method of Feldman and Cousins, they obtain {Beta}(B{sup +} {yields} {tau}{sup +}{nu}{sub {tau}}) = (1.7 {+-} 0.8 {+-} 0.2) x 10{sup -4}, which excludes zero at 2.3{sigma}. They interpret the central value in the context of the Standard Model and find the B meson decay constant to be f{sub B}{sup 2} = (62 {+-} 31) x 10{sup 3} MeV{sup 2}. They find no evidence for B{sup +} {yields} e{sup +}{nu}{sub e} and B{sup +} {yields} {mu}{sup +}{nu}{sub {mu}} and set upper limits at the 90% C.L. {Beta}(B{sup +} {yields} e{sup +}{nu}{sub e}) < 0.8 x 10{sup -5} and {Beta}(B{sup +} {yields} {mu}{sup +}{nu}{sub {mu}}) < 1.1 x 10{sup -5}.
Date: December 17, 2009
Creator: Aubert, B.
Partner: UNT Libraries Government Documents Department

Search for High-Mass Resonances Decaying into Leptons of Different Flavor (e mu, e tau, mu tau) in p anti-p Collisions at sqrt(s) = 1.96 TeV

Description: We present a search for high-mass resonances decaying into two leptons of different flavor: e{mu}, e{tau}, and {mu}{tau}. These resonances are predicted by several models beyond the standard model, such as the R-parity-violating MSSM. The search is based on 1 fb{sup -1} of data collected at the Collider Detector at Fermilab (CDF II) in proton anti-proton collisions. Our observations are consistent with the standard model expectations. The results are interpreted to set 95% C.L. upper limits on {sigma} x BR of {tilde {nu}}{sub {tau}} {yields} e{mu}, e{tau}, {mu}{tau}.
Date: October 1, 2008
Creator: Tu, Yanjun & U., /Pennsylvania
Partner: UNT Libraries Government Documents Department

Study of the k+ to pi+, neutrino, anti-neutrino decay in the momentum region p(pi+) < 199 MeV/C

Description: Experiment E949 at Brookhaven National Laboratory has observed three candidate events for the decay K{sup +} {yields} {pi}{sup +}{nu}{bar {nu}} in the pion momentum region 140 &lt; P{sub {pi}} &lt; 199 MeV/c in a exposure of 1.71 x 10{sup 12} stopped kaons with an estimated total background of 0.93 {+-} 0.17(stat.){sub -0.24}{sup +0.32}(syst.) events. Combination of this observation with previous results, assuming a pion spectrum as predicted by the standard model, produces a branching fraction of {beta} = (1.73{sub -1.05}{sup +1.15}) x 10{sup -10}. We also give the interpretation of the combined results for alternative model of the decay K{sup +} {yields} {pi}{sup +} + nothing.
Date: January 1, 2009
Creator: Artamonov, A.V.; Bassalleck, B.; Bhuyan, B.; Blackmore, E.W.; Bryman, D.A.; Chen, S. et al.
Partner: UNT Libraries Government Documents Department

A Search for the Rare Decay B0 to tau+tau- atBaBar

Description: We present the results of a search for the decay B{sup 0} {yields} {tau}{sup +}{tau}{sup -} in a data sample of (232 {+-} 3) x 10{sup 6} {Upsilon}(4S) {yields} B{bar B} decays using the BABAR detector. Certain extensions of the Standard Model predict measurable levels of this otherwise rare decay. We reconstruct fully one neutral B meson and seek evidence for the signal decay in the rest of the event. We find no evidence for signal events and obtain {Beta}(B{sup 0} {yields} {tau}{sup +}{tau}{sup -}) &lt; 3.2 x 10{sup -3} at the 90% confidence level.
Date: November 9, 2005
Creator: Aubert, B.; Barate, R.; Boutigny, D.; Couderc, F.; Karyotakis, Y.; Lees, J. P. et al.
Partner: UNT Libraries Government Documents Department

Measurement of Time-Dependent CP Asymmetries and the CP-Odd Fraction in the Decay B0->D*+D*-

Description: We present an updated measurement of time-dependent CP asymmetries and the CP-odd fraction in the decay B{sup 0} D*{sup +}D*{sup -} using 232 x 10{sup 6} B{bar B} pairs collected by the BABAR detector at the PEP-II B factory. We determine the CP-odd fraction to be 0.125 {+-} 0.044(stat) {+-} 0.007(syst). The time-dependent CP asymmetry parameters C{sub +} and S{sub +} are determined to be 0.06 {+-} 0.17(stat) {+-} 0.03(syst) and -0.75 {+-} 0.25(stat) {+-} 0.03(syst), respectively. The Standard Model predicts these parameters to be 0 and -sin2{beta}, respectively, in the absence of penguin amplitude contributions.
Date: July 6, 2005
Creator: Aubert, B.; Barate, R.; Boutigny, D.; Couderc, F.; Karyotakis, Y.; Lees, J. P. et al.
Partner: UNT Libraries Government Documents Department

Search for signatures of extra dimensions in the diphoton mass spectrum at the Large Hadron Collider

Description: A search for signatures of extra dimensions in the diphoton invariant-mass spectrum has been performed with the CMS detector at the LHC. No excess of events above the standard model expectation is observed using a data sample collected in proton-proton collisions at {radical}s = 7 TeV corresponding to an integrated luminosity of 2.2 fb{sup -1}. In the context of the large-extra-dimensions model, lower limits are set on the effective Planck scale in the range of 2.3-3.8 TeV at the 95% confidence level. These limits are the most restrictive bounds on virtual-graviton exchange to date. The most restrictive lower limits to date are also set on the mass of the first graviton excitation in the Randall-Sundrum model in the range of 0.86-1.84 TeV, for values of the associated coupling parameter between 0.01 and 0.10.
Date: December 1, 2011
Creator: Chatrchyan, Serguei; Khachatryan, Vardan; Sirunyan, Albert M.; Tumasyan, Armen; Adam, Wolfgang; Bergauer, Thomas et al.
Partner: UNT Libraries Government Documents Department

Measurement of the K+ --> pi+ nu nu branching ratio

Description: Experiment E949 at Brookhaven National Laboratory studied the rare decay K{sup +}--&gt;pi{sup +} nu{ovr {nu}} and other processes with an exposure of 1.77 x 10{sup 12} k{sup +}'s. The data were analyzed using a blind analysis technique yielding one candidate event with an estimated background of 0.30 {+-} 0.03 events. Combining this result with the observation of two candidate events by the predecessor experiment E787 gave the branching ratio B(K{sup +}--&gt;pi{sup +} nu{ovr {nu}}) = (1.47{sub -0.89}{sup +1.30}) x 10{sup -10}, consistent with the standard model prediction of (0.74 {+-} 0.20) x 10{sup -10}. This is a more detailed report of results previously published [V.V. Anisimovsky et al., Phys. Rev. Lett. 93, 031801 (2004)].
Date: March 1, 2008
Creator: Adler, S.; Anisimovsky, V. V.; Aoki, M.; Ardebili, M.; Artamonov, A. V.; Atiya, M. et al.
Partner: UNT Libraries Government Documents Department

Search for associated Higgs boson production WH ---> WWW* ---> l+- nu l-prime+- nu-prime + X in p anti-p collisions at s**(1/2) = 1.96-TeV

Description: The authors present a search for associated Higgs boson production in the process p{bar p} {yields} WH {yields} WWW* {yields} {ell}{sup {+-}}{nu} {ell}{prime}{sup {+-}} {nu}{prime} + X in final states containing two like-sign isolated electrons or muons (e{sup {+-}}e{sup {+-}}, e{sup {+-}} {mu}{sup {+-}}, or {mu}{sup {+-}} {mu}{sup {+-}}). The search is based on D0 Run II data samples corresponding to integrated luminosities of 360-380 pb{sup -1}. No excess is observed over the predicted standard model background. They set 95% C.L. upper limits on {sigma}(p{bar p} {yields} WH) x Br(H {yields} WW*) between 3.2 and 2.8 pb for Higgs masses from 115 to 175 GeV.
Date: July 1, 2006
Creator: Abazov, V. M.; Abbott, B.; Abolins, M.; Acharya, B. S.; Adams, M.; Adams, T. et al.
Partner: UNT Libraries Government Documents Department

Non-susy exotics searches at the Tevatron

Description: The authors present results of searches for signs of physics beyond the Standard Model. The focus of this paper is on analyses not driven by SUSY models. Most of the presented results are based on {approx} 2 fb{sup -1} of data and obtained since summer of 2007. No significant excess of data over predicted background is observed. They report kinematic distributions, data and background counts, as well as limits on some parameters of selected models of new physics.
Date: May 1, 2008
Creator: Pronko, Alexandre
Partner: UNT Libraries Government Documents Department

Radiative b to d Penguins

Description: This article gives an overview of the recent searches and measurements of b {yields} d penguin transitions with the BaBar experiment. The branching fraction of these decays in the Standard Model (SM) is expected to be a factor of 10 or more lower than the corresponding b {yields} s penguin transitions, but a deviation from the SM prediction would be an equally striking sign of new physics. The exclusive decay B {yields} {pi}{ell}{ell} is searched by BaBar with no excess over the background found. The BaBar measurement of B {yields} ({rho}, {omega}){gamma} provides the first evidence of B{sup +} {yields} {rho}{sup +}{gamma}, {sup c} is in good agreement with the previous Belle results and provides a measurement of |V{sub td}/V{sub ts}| independent of the one from Bs mixing. No deviation from the SM is found.
Date: June 13, 2007
Creator: Bechtle, P.
Partner: UNT Libraries Government Documents Department

Seach for second - generation leptoquarks in proton - anti-proton collisions

Description: This document describes the search for second-generation leptoquarks (LQ{sub 2}) in around 114pb{sup -1} of p{bar p} collisions, recorded with the D0 detector between September 2002 and June 2003 at a centre-of-mass energy of {radical}s = 1.96TeV. The predictions of the Standard Model and models including scalar leptoquark production are compared to the data for various kinematic distributions. Since no excess of data over the Standard Model prediction has been observed, a lower limit on the leptoquark mass of M{sub LQ{sub 2}}{sup {beta}=1} &gt; 200GeV has been calculated at 95% confidence level (C.L.), assuming a branching fraction of {beta} = BF(LQ{sub 2} {yields} {mu}j) = 100% into a charged lepton and a quark. The corresponding limit for {beta} = 1/2 is M{sub LQ{sub 2}}{sup {beta}=1/2} &gt; 152 GeV. Finally, the results were combined with those from the search in the same channel at D0 Run I. This combination yields the exclusion limit of M{sub LQ{sub 2}}{sup {beta}=1} &gt; 222 GeV (177GeV) for (beta) = 1 (1/2) at 95% C.L., which is the best exclusion limit for scalar second-generation leptoquarks (for {beta} = 1) from a single experiment to date.
Date: December 1, 2003
Creator: Christiansen, Tim U. & U., /Munich
Partner: UNT Libraries Government Documents Department

Search for compositeness in dilepton final states at D0

Description: We report preliminary results of a search for substructure in quarks and leptons assuming a four-fermion contact interaction for dielectron pairs of large invariant mass. The search is based on dielectron data collected by the D0 detector in p{bar p} collisions a {radical}s = 1.96 TeV. The results agree well with predictions of the standard model and we obtain model-dependent lower limits at 95% confidence level on the compositeness scale of 3.6 to 9.1 TeV for different chiral models of the composite structure of quarks and electrons.
Date: December 1, 2004
Creator: Chakrabarti, Subhendu & Inst., /Tata
Partner: UNT Libraries Government Documents Department

Measurement of the Drell-Yan Differential Cross Section and Forward - Backward Asymmetry in proton anti-proton --> e+ e- Events using the D0 Detector

Description: We present measurements of the inclusive Drell-Yan e{sup +}e{sup -} differential cross section (d{sigma}/dM{sub e{sup +}e{sup -}}) and forward-backward asymmetry (A{sub FB}) as a function of the dielectron invariant mass over the range 70-400 GeV/c{sup 2}. The data sample consists of 177.3 pb{sup -1} of p{bar p} collisions at {radical}s = 1.96 TeV collected by the D0 detector. The results are consistent with the predictions of the standard model.
Date: August 1, 2005
Creator: Gelhaus, Raymond & /UC, Riverside
Partner: UNT Libraries Government Documents Department

Measurement of the t anti-t production cross-section at s**(1/2) = 1.96-TeV using lifetime tagging

Description: A measurement of the t{bar t} production cross section in the lepton+jets channels with the D0 detector at {radical}s = 1.96 TeV using the lifetime-tagging techniques is presented. The t{bar t} cross section is estimated from the combination of the e+jets and {mu}+jets channels. The obtained result {sigma}{sub t{bar t}} = 7.47{sub -1.14}{sup +1.22}(stat){sub -1.03}{sup +1.65}(syst) {+-} 0.49(lumi) pb is consistent with the Standard Model expectation.
Date: July 1, 2004
Creator: Khanov, Alexander & U., /Rochester
Partner: UNT Libraries Government Documents Department

First Flavor-Tagged Determination of Bounds on Mixing-Induced CP Violation in B^0_s --> j/psi phi Decays

Description: This Letter describes the first determination 1 of bounds on the CP-violation parameter 2{beta}{sub s} using B{sub s}{sup 0} decays in which the flavor of the bottom meson at production is identified. The result is based on approximately 2, 000 B{sub s}{sup 0} {yields} J/{psi}{phi} decays reconstructed in a 1.35 fb{sup -1} data sample collected with the CDFII detector using p{bar p} collisions produced at the Fermilab Tevatron. We report confidence regions in the two-dimensional space of 2{beta}{sub s} and the decay-width difference {Delta}{Lambda}. Assuming the standard model predictions of 2{beta}{sub s} and {Delta}{Lambda}, the probability of a deviation as large as the level of the observed data is 15%, corresponding to 1.5 Gaussian standard deviations.
Date: December 1, 2007
Creator: CDF Collaboration
Partner: UNT Libraries Government Documents Department