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Top quark pair production cross section at the Tevatron

Description: Top quark pair production cross section has been measured at the Tevatron by CDF and D0 collaborations using different channels and methods, in order to test standard model predictions, and to search for new physics hints affecting the t{bar t} production mechanism or decay. Measurements are carried out with an integrated luminosity of 1.0 to 2.0 fb{sup -1}, and are found to be consistent with standard model expectations.
Date: April 1, 2008
Creator: Cortiana, Giorgio & /INFN, Padua /Padua U.
Partner: UNT Libraries Government Documents Department

Performance study of GPUs in real-time trigger applications for HEP experiments

Description: Graphical Processing Units (GPUs) have evolved into highly parallel, multi-threaded, multicore powerful processors with high memory bandwidth. GPUs are used in a variety of intensive computing applications. The combination of highly parallel architecture and high memory bandwidth makes GPUs a potentially promising technology for effective real-time processing for High Energy Physics (HEP) experiments. However, not much is known of their performance in real-time applications that require low latency, such as the trigger for HEP experiments. We describe an R and D project with the goal to study the performance of GPU technology for possible low latency applications, performing basic operations as well as some more advanced HEP lower-level trigger algorithms (such as fast tracking or jet finding). We present some preliminary results on timing measurements, comparing the performance of a CPU versus a GPU with NVIDIA's CUDA general-purpose parallel computing architecture, carried out at CDF's Level-2 trigger test stand. These studies will provide performance benchmarks for future studies to investigate the potential and limitations of GPUs for real-time applications in HEP experiments.
Date: June 1, 2011
Creator: Ketchum, W.; U., /Chicago; Amerio, S.; /INFN, Padua; Bastieri, D.; Bauce, M. et al.
Partner: UNT Libraries Government Documents Department

An Index for the Dirac Operator on D3 Brane withBackground Fluxes

Description: We study the problem of instanton generated superpotentials in Calabi-Yau orientifold compactifications directly in type IIB string theory. To this end, we derive the Dirac equation on a Euclidean D3 brane in the presence of background fluxes. We propose an index which governs whether the generation of a superpotential in the effective 4d theory by D3 brane instantons is possible. Applying the formalism to various classes of examples, including the K3 x T{sup 2}/Z{sub 2} orientifold, in the absence and presence of fluxes, we show that our results are consistent with conclusions attainable via duality from an M-theory analysis.
Date: August 3, 2005
Creator: Bergshoeff, Eric; U., /Groningen; Kallosh, Renata; /Stanford U., Phys. Dept. /Kyoto U., Yukawa Inst., Kyoto; Kashani-Poor, Amir-Kian; /Stanford U., Phys. Dept. /SLAC et al.
Partner: UNT Libraries Government Documents Department

Study of multi-muon events produced in p anti-p interactions at s**(1/2) = 1.96-TeV

Description: We report the results of a study of multi-muon events produced at the Fermilab Tevatron collider and acquired with the CDF II detector using a dedicated dimuon trigger. The production cross section and kinematics of events in which both muon candidates are produced inside the beam pipe of radius 1.5 cm are successfully modeled by known processes which include heavy flavor production. In contrast, we are presently unable to fully account for the number and properties of the remaining events, in which at least one muon candidate is produced outside of the beam pipe, in terms of the same understanding of the CDF II detector, trigger, and event reconstruction.
Date: June 12, 2010
Creator: Aaltonen, T.; Phys., /Helsinki Inst. of; Adelman, J.; /Chicago U., EFI; Alvarez Gonzalez, B.; Phys., /Cantabria Inst. of et al.
Partner: UNT Libraries Government Documents Department

The On-Orbit Calibrations for the Fermi Large Area Telescope

Description: The Large Area Telescope (LAT) on-board the Fermi Gamma-ray Space Telescope began its on-orbit operations on June 23, 2008. Calibrations, defined in a generic sense, correspond to synchronization of trigger signals, optimization of delays for latching data, determination of detector thresholds, gains and responses, evaluation of the perimeter of the South Atlantic Anomaly (SAA), measurements of live time, of absolute time, and internal and spacecraft boresight alignments. Here we describe on-orbit calibration results obtained using known astrophysical sources, galactic cosmic rays, and charge injection into the front-end electronics of each detector. Instrument response functions will be described in a separate publication. This paper demonstrates the stability of calibrations and describes minor changes observed since launch. These results have been used to calibrate the LAT datasets to be publicly released in August 2009.
Date: November 17, 2011
Creator: Abdo, Aous A.; /Naval Research Lab, Wash., D.C.; Ackermann, M.; /Stanford U., HEPL /KIPAC, Menlo Park /Stanford U., Phys. Dept.; Ajello, M.; /Stanford U., HEPL /KIPAC, Menlo Park /Stanford U., Phys. Dept. et al.
Partner: UNT Libraries Government Documents Department

The Large Area Telescope on the Fermi Gamma-ray Space Telescope Mission

Description: The Large Area Telescope (Fermi/LAT, hereafter LAT), the primary instrument on the Fermi Gamma-ray Space Telescope (Fermi) mission, is an imaging, wide field-of-view (FoV), high-energy {gamma}-ray telescope, covering the energy range from below 20 MeV to more than 300 GeV. The LAT was built by an international collaboration with contributions from space agencies, high-energy particle physics institutes, and universities in France, Italy, Japan, Sweden, and the United States. This paper describes the LAT, its preflight expected performance, and summarizes the key science objectives that will be addressed. On-orbit performance will be presented in detail in a subsequent paper. The LAT is a pair-conversion telescope with a precision tracker and calorimeter, each consisting of a 4 x 4 array of 16 modules, a segmented anticoincidence detector that covers the tracker array, and a programmable trigger and data acquisition system. Each tracker module has a vertical stack of 18 (x, y) tracking planes, including two layers (x and y) of single-sided silicon strip detectors and high-Z converter material (tungsten) per tray. Every calorimeter module has 96 CsI(Tl) crystals, arranged in an eight-layer hodoscopic configuration with a total depth of 8.6 radiation lengths, giving both longitudinal and transverse information about the energy deposition pattern. The calorimeter's depth and segmentation enable the high-energy reach of the LAT and contribute significantly to background rejection. The aspect ratio of the tracker (height/width) is 0.4, allowing a large FoV (2.4 sr) and ensuring that most pair-conversion showers initiated in the tracker will pass into the calorimeter for energy measurement. Data obtained with the LAT are intended to (1) permit rapid notification of high-energy {gamma}-ray bursts and transients and facilitate monitoring of variable sources, (2) yield an extensive catalog of several thousand high-energy sources obtained from an all-sky survey, (3) measure spectra from 20 MeV to more than ...
Date: May 15, 2009
Creator: Atwood, W.B.; /UC, Santa Cruz; Abdo, Aous A.; /Naval Research Lab, Wash., D.C.; Ackermann, M.; /Stanford U., HEPL /KIPAC, Menlo Park /Stanford U., Phys. Dept. et al.
Partner: UNT Libraries Government Documents Department

Design and Initial Tests of the Tracker-Converter ofthe Gamma-ray Large Area Space Telescope

Description: The Tracker subsystem of the Large Area Telescope (LAT) science instrument of the Gamma-ray Large Area Space Telescope (GLAST) mission has been completed and tested. It is the central detector subsystem of the LAT and serves both to convert an incident gamma-ray into an electron-positron pair and to track the pair in order to measure the gamma-ray direction. It also provides the principal trigger for the LAT. The Tracker uses silicon strip detectors, read out by custom electronics, to detect charged particles. The detectors and electronics are packaged, along with tungsten converter foils, in 16 modular, high-precision carbon-composite structures. It is the largest silicon-strip detector system ever built for launch into space, and its aggressive design emphasizes very low power consumption, passive cooling, low noise, high efficiency, minimal dead area, and a structure that is highly transparent to charged particles. The test program has demonstrated that the system meets or surpasses all of its performance specifications as well as environmental requirements. It is now installed in the completed LAT, which is being prepared for launch in early 2008.
Date: April 16, 2007
Creator: Atwood, W.B.; Bagagli, R.; Baldini, L.; Bellazzini, R.; Barbiellini, G.; Belli, F. et al.
Partner: UNT Libraries Government Documents Department

Observation of the Baryonic B decay B0bar to Lambda_c^+ anti-Lambda K-

Description: The authors report the observation of the baryonic B decay {bar B}{sup 0} {yields} {Lambda}{sub c}{sup +} {bar {Lambda}}K{sup -} with a significance larger than 7 standard deviations based on 471 x 10{sup 6} B{bar B} pairs collected with the BABAR detector at the PEP-II storage ring at SLAC. They measure the branching fraction for the decay {bar B}{sup 0} {yields} {Lambda}{sub c}{sup +} {bar {Lambda}}K{sup -} to be (3.8 {+-} 0.8{sub stat} {+-} 0.2{sub sys} {+-} 1.0 {sub {Lambda}{sub c}{sup +}}) x 10{sup -5}. The uncertainties are statistical, systematic, and due to the uncertainty in the {Lambda}{sub c}{sup +} branching fraction. They find that the {Lambda}{sub c}{sup +} K{sup -} invariant mass distribution shows an enhancement above 3.5 GeV/c{sup 2}.
Date: November 8, 2011
Creator: Lees, J.P.; Poireau, V.; Tisserand, V.; /Annecy, LAPP; Garra Tico, J.; Grauges, E. et al.
Partner: UNT Libraries Government Documents Department

Fermi Large Area Telescope First Source Catalog

Description: Abstract Not Provided
Date: July 8, 2013
Creator: Abdo, A.A.; /Naval Research Lab, Wash., D.C. /Federal City Coll.; Ackermann, M.; /Stanford U., HEPL /KIPAC, Menlo Park /Stanford U., Phys. Dept.; Ajello, M.; /Stanford U., HEPL /KIPAC, Menlo Park /Stanford U., Phys. Dept. et al.
Partner: UNT Libraries Government Documents Department

Search for CP Violation in the Decay D+/- to Ks pi+/-

Description: We report on a search for CP violation in the decay D{sup {+-}} {yields} K{sub S}{sup 0}{pi}{sup {+-}} using a data set corresponding to an integrated luminosity of 469 fb{sup -1} collected with the BABAR detector at the PEP-II asymmetric energy e{sup +}e{sup -} storage rings. The CP-violating decay rate asymmetry A{sub CP} is determined to be (-0.44 {+-} 0.13(stat) {+-} 0.10(syst))%, consistent with zero at 2.7 {sigma} and with the standard model prediction of (-0.332 {+-} 0.006)%. This is currently the most precise measurement of this parameter.
Date: August 22, 2011
Creator: del Amo Sanchez, P.; Lees, J.P.; Poireau, V.; Prencipe, E.; Tisserand, V.; /Annecy, LAPP et al.
Partner: UNT Libraries Government Documents Department

B-meson decays to eta' rho, eta' f0, and eta' K*

Description: We present measurements of B-meson decays to the final states {eta}{prime} {rho}, {eta}{prime} f{sub 0}, and {eta}{prime} K*, where K* stands for a vector, scalar, or tensor strange meson. We observe a significant signal or evidence for {eta}{prime} {rho}{sup +} and all the {eta}{prime}K* channels. We also measure, where applicable, the charge asymmetries, finding results consistent with no direct CP violation in all cases. The measurements are performed on a data sample consisting of 467 x 10{sup 6} B{bar B} pairs, collected with the BABAR detector at the PEP-II e{sup +}e{sup -} collider at the SLAC National Accelerator Laboratory. Our results favor the theoretical predictions from perturbative QCD and QCD Factorization and we observe an enhancement of the tensor K*{sub 2} (1430) with respect to the vector K*(892) component.
Date: August 25, 2010
Creator: del Amo Sanchez, P.; Lees, J.P.; Poireau, V.; Prencipe, E.; Tisserand, V.; /Annecy, LAPP et al.
Partner: UNT Libraries Government Documents Department

Exclusive Production of Ds Ds-, Ds* Ds-, and Ds* Ds*- via e e- Annihilation with Initial-State-Radiation

Description: The authors perform a study of exclusive production of D{sub s}{sup +}D{sub s}{sup -}, D*{sub s}{sup +}D{sub s}{sup -}, and D*{sub s}{sup +}D*{sub s}{sup -} final states in initial-state-radiation events from e{sup +}e{sup -} annihilations at a center-of-mass energy near 10.58 GeV, to search for charmonium 1{sup --} states. The data sample corresponds to an integrated luminosity of 525 fb{sup -1} and was recorded by the BABAR experiment at the PEP-II storage ring. The D{sub s}{sup +} D{sub s}{sup -}, D*{sub s}{sup +}D{sub s}{sup -}, and D*{sub s}{sup +}D*{sub s}{sup -} mass spectra show evidence of the known {psi} resonances. Limits are extracted for the branching ratios of the decays X(4260) {yields} D{sub s}{sup (*)+}D{sub s}{sup (*)-}.
Date: October 27, 2010
Creator: del Amo Sanchez, P.; Lees, J.P.; Poireau, V.; Prencipe, E.; Tisserand, V.; /Annecy, LAPP et al.
Partner: UNT Libraries Government Documents Department

Measurement of CP violation observables and parameters for the decays $B^{\pm}\to DK^{*\pm}$

Description: We study the decay B{sup -} {yields} DK*{sup -} using a sample of 379 x 10{sup 6} {Upsilon}(4S) {yields} B{bar B} events collected with the BABAR detector at the PEP-II B-factory. We perform a 'GLW' analysis where the D meson decays into either a CP-even (CP+) eigenstate (K{sup +}K{sup -}, {pi}{sup +}{pi}{sup -}), CP-odd (CP-) eigenstate (K{sub S}{sup 0}{pi}{sup 0}, K{sub S}{sup 0}{phi}, K{sub S}{sup 0}{omega}) or a non-CP state (K{sup -}{pi}{sup +}). We also analyze D meson decays into K{sup +}{pi}{sup -} from a Cabibbo-favored {bar D}{sup 0} decay or doubly suppressed D{sup 0} decay ('ADS' analysis). We measure observables that are sensitive to the CKM angle {gamma}: the partial-rate charge asymmetries A{sub CP{+-}}, the ratios R{sub CP{+-}} of the B-decay branching fractions in CP{+-} and non-CP decay, the ratio R{sub ADS} of the charge-averaged branching fractions, and the charge asymmetry A{sub ADS} of the ADS decays: A{sub CP+} = 0.09 {+-} 0.13 {+-} 0.06, A{sub CP-} = -0.23 {+-} 0.21 {+-} 0.07, R{sub CP+} = 2.17 {+-} 0.35 {+-} 0.09, R{sub CP-} = 1.03 {+-} 0.27 {+-} 0.13, R{sub ADS} = 0.066 {+-} 0.031 {+-} 0.010, and A{sub ADS} = -0.34 {+-} 0.43 {+-} 0.16, where the first uncertainty is statistical and the second is systematic. Combining all the measurements and using a frequentist approach yields the magnitude of the ratio between the Cabibbo-suppressed and favored amplitudes, r{sub B} = 0.31 with a one (two) sigma confidence level interval of [0.24, 0.38] ([0.17, 0.43]). The value r{sub B} = 0 is excluded at the 3.3 sigma level. A similar analysis excludes values of {gamma} in the intervals [0, 7]{sup o}, [55, 111]{sup o}, and [175, 180]{sup o} ([85, 99]{sup o}) at the one (two) sigma confidence level.
Date: August 26, 2010
Creator: Aubert, Bernard; Karyotakis, Y.; Lees, J.P.; Poireau, V.; Prencipe, E.; Prudent, X. et al.
Partner: UNT Libraries Government Documents Department

Measurement of the Branching Fraction for D8+ rarr tau+nu_tau and Extraction of the Decay Constant f_D_s

Description: The branching fraction for the decay D{sub s}{sup +} {yields} {tau}{sup +}{nu}{sub {tau}} with {tau}{sup +} {yields} e{sup +}{bar {nu}}{sub {tau}}, is measured using a data sample corresponding to an integrated luminosity of 427 fb{sup -1} collected at center of mass energies near 10.58 GeV with the BABAR detector at the PEP-II asymmetric-energy e{sup +}e{sup -} collider at SLAC. In the process e{sup +}e{sup -} {yields} c{bar c} {yields} D*{sub s}{sup +} {bar D}{sub TAG}{bar K}X, the D*{sub s}{sup +} meson is reconstructed as a missing particle, and the subsequent decay D*{sub s}{sup +} {yields} D{sub s}{sup +}{gamma} yields an inclusive D{sub s}{sup +} data sample. Here {bar D}{sub TAG} refers to a fully reconstructed hadronic {bar D} decay, {bar K} is a K{sup -} or {bar K}{sup 0}, and X stands for any number of charged or neutral pions. The decay D{sub s}{sup +} {yields} K{sub S}{sup 0}K{sup +} is isolated also, and from ratio of event yields and known branching fractions, {Beta}(D{sub s}{sup +} {yields} {tau}{sup +}{nu}{sub {tau}}) = (4.5 {+-} 0.5 {+-} 0.4 {+-} 0.3)% is determined. The pseudoscalar decay constant is extracted to be f{sub D{sub s}} = (233 {+-} 13 {+-} 10 {+-} 7) MeV, where the first uncertainty is statistical, the second is systematic, and the third results from the uncertainties on the external measurements used as input to the calculation.
Date: June 4, 2010
Creator: Lees, J.P.; Poireau, V.; Prencipe, E.; Tisserand, V.; /Annecy, LAPP; Garra Tico, J. et al.
Partner: UNT Libraries Government Documents Department

Observation of the Upsilon(13DJ ) Bottomonium State through Decays to pi+pi-Upsilon(1S)

Description: Based on 122X10{sup 6} {upsilon}(3S) events collected with the BABAR detector, we have observed the {upsilon}(1{sup 3}D{sub J}) bottomonium state through the {upsilon}(3S){yields}{gamma}{gamma}{upsilon}(1{sup 3}D{sub J}){yields}{gamma}{gamma}{pi}{sub +}{pi}{sub -}{upsilon}(1S) decay chain. The significance is 6.2 standard deviations including systematic uncertainties. The mass of the J = 2 member of the {upsilon}(1{sup 3}D{sub J}) triplet is determined to be 10164.5{-+}0.8 (stat.) {-+} 0.5 (syst.) MeV/c{sup 2}. We use the {pi}{sup +}{pi}{sup -} invariant mass and decay angular distributions to confirm the consistency of the observed state with the orbital angular momentum and parity assignments of the {upsilon}(1{sup 3}D{sub J}).
Date: June 2, 2010
Creator: del Amo Sanchez, P.; Lees, J.P.; Poireau, V.; Prencipe, E.; Tisserand, V.; /Annecy, LAPP et al.
Partner: UNT Libraries Government Documents Department

Search for Production of Invisible Final States in Single-Photon Decays of Upsilon(1S)

Description: We search for single-photon decays of the {Upsilon}(1S) resonance, {Upsilon} {yields} {gamma} + invisible, where the invisible state is either a particle of definite mass, such as a light Higgs boson A{sup 0}, or a pair of dark matter particles, {chi}{bar {chi}}. Both A{sup 0} and {chi} are assumed to have zero spin. We tag {Upsilon}(1S) decays with a dipion transition {Upsilon}(2S) {yields} {pi}{sup +}{pi}{sup -}{Upsilon}(1S) and look for events with a single energetic photon and significant missing energy. We find no evidence for such processes in the mass range m{sub A{sup o}} {le} 9.2GeV and m{sub {chi}} {le} 4.5GeV in the sample of 98 x 10{sup 6} {Upsilon}(2S) decays collected with the BABAR detector and set stringent limits on new physics models that contain light dark matter states.
Date: August 25, 2010
Creator: del Amo Sanchez, P.; Lees, J.P.; Poireau, V.; Prencipe, E.; Tisserand, V.; /Annecy, LAPP et al.
Partner: UNT Libraries Government Documents Department

Measurement of the gamma gamma* to eta_c transition form factor

Description: The authors study the reaction e{sup +}e{sup -} {yields} e{sup +}e{sup -} {eta}{sub c}, {eta}{sub c} {yields} K{sub S}K{sup {+-}}{pi}{sup {-+}} and obtain {eta}{sub c} mass and width values 2982.2 {+-} 0.4 {+-} 1.6 MeV/c{sup 2} and 31.7 {+-} 1.2 {+-} 0.8 MeV, respectively. They find {Lambda}({eta}{sub c} {yields} {gamma}{gamma}){Beta}({eta}{sub c} {yields} K{bar K}{pi}) = 0.374 {+-} 0.009 {+-} 0.031 keV, and measure the {gamma}{gamma}* {yields} {eta}{sub c} transition form factor in the momentum transfer range from 2 to 50 GeV{sup 2}. The analysis is based on 469 fb{sup -1} of integrated luminosity collected at PEP-II with the BABAR detector at e{sup +}e{sup -} center-of-mass energies near 10.6 GeV.
Date: April 28, 2010
Creator: Lees, J.P.; Poireau, V.; Prencipe, E.; Tisserand, V.; /Annecy, LAPP; Garra Tico, J. et al.
Partner: UNT Libraries Government Documents Department

Observation of the Rare Decay B+ \to K+pi0pi0 and Measurement of the Quasi-two Body Contributions B+ \to K*(892)+pi0, B+ \to f0(980)K+ and B+ \to chic0K+

Description: We report an analysis of charmless hadronic decays of charged B mesons to the final state K{sup +}{pi}{sup 0}{pi}{sup 0}, using a data sample of (470.9 {+-} 2.8) x 10{sup 6} B{bar B} events collected with the BABAR detector at the {Gamma}(4S) resonance. We observe an excess of signal events, with a significance above 10 standard deviations including systematic uncertainties, and measure the branching fraction and CP asymmetry to be {Beta}(B{sup +} {yields} K{sup +}{pi}{sup 0}{pi}{sup 0}) = (16.2 {+-} 1.2 {+-} 1.5) x 10{sup -6} and A{sub CP}(B{sup +} {yields} K{sup +}{pi}{sup 0}{pi}{sup 0}) = -0.06 {+-} 0.06 {+-} 0.04, where the uncertainties are statistical and systematic, respectively. Additionally, we study the contributions of the B{sup +} {yields} K{sup +}(892){sup +}{pi}{sup 0}, B{sup +} {yields} f{sub 0}(980)K{sup +}, and B{sup +} {yields} {chi}{sub c0}K{sup +} quasi-two-body decays. We report the world's best measurements of the branching fraction and CP asymmetry of the B{sup +} {yields} K{sup +}{pi}{sup 0}{pi}{sup 0} and B{sup +} {yields} K{sup +}(892){sup +}{pi}{sup 0} channels.
Date: December 13, 2011
Creator: Lees, J.P.; Poireau, V.; Tisserand, V.; /Annecy, LAPP; Garra Tico, J.; Grauges, E. et al.
Partner: UNT Libraries Government Documents Department

Evidence for Direct CP Violation in the Measurement of the Cabibbo-Kobayashi-Maskawa Angle gamma with B-+ to D(*) K(*)-+ Decays

Description: We report the measurement of the Cabibbo-Kobayashi-Maskawa CP-violating angle {gamma} through a Dalitz plot analysis of neutral D meson decays to K{sub S}{sup 0}{pi}{sup +}{pi}{sup -} and K{sub S}{sup 0} K{sup +}K{sup -} produced in the processes B{sup {-+}} {yields} DK{sup {-+}}, B{sup {-+}} {yields} D* K{sup {-+}} with D* {yields} D{pi}{sup 0}, D{gamma}, and B{sup {-+}} {yields} DK*{sup {-+}} with K*{sup {-+}} {yields} K{sub S}{sup 0}{pi}{sup {-+}}, using 468 million B{bar B} pairs collected by the BABAR detector at the PEP-II asymmetric-energy e{sup +}e{sup -} collider at SLAC. We measure {gamma} = (68 {+-} 14 {+-} 4 {+-} 3){sup o} (modulo 180{sup o}), where the first error is statistical, the second is the experimental systematic uncertainty and the third reflects the uncertainty in the description of the neutral D decay amplitudes. This result is inconsistent with {gamma} = 0 (no direct CP violation) with a significance of 3.5 standard deviations.
Date: August 19, 2011
Creator: del Amo Sanchez, P.; Lees, J.P.; Poireau, V.; Prencipe, E.; Tisserand, V.; /Annecy, LAPP et al.
Partner: UNT Libraries Government Documents Department

Evidence for B+ --> tau+ nu_tau Decays using Hadronic B Tags

Description: We present a search for the decay B{sup +} --> {tau}{sup +} {nu}{sub {tau}} using 467.8 x 10{sup 6} B{anti B} pairs collected at the {Upsilon}(4S) resonance with the BABAR detector at the SLAC PEP-II B-Factory. We select a sample of events with on completely reconstructed B{sup -} in an hadronic decay mode (B{sup -} --> D{sup (*)0}X{sup -} and B{sup -} --> J/{psi} X{sup -}). We examine the rest of the event to search for a B{sup +} --> {tau}{sup +} {nu}{sub {tau}} decay. We identify the {tau}{sup +} lepton in the following modes: {tau}{sup +} --> e{sup +} {nu}{sub e}{anti {nu}}{sub {tau}}, {tau}{sup +} --> {mu}{sup +} {nu}{sub {mu}}{anti {nu}}{sub {tau}}, {tau}{sup +} --> {pi}{sup +}{anti {nu}}{sub {tau}} and {tau}{sup +} --> {rho}{anti {nu}}{sub {tau}}. We find an excess of events with respect to expected background, which excludes the null signal hypothesis at the level of 3.3 {sigma} and can be converted to a branching fraction central value of B(B{sup +} --> {tau}{sup +} {nu}{sub {tau}})= (1.80{sup + 0.57}{sub - 0.54}(stat.) {+-} 0.26 (syst.)) x 10{sup -4}.
Date: August 11, 2011
Creator: del Amo Sanchez, P.; Lees, J.P.; Poireau, V.; Prencipe, E.; Tisserand, V.; /Annecy, LAPP et al.
Partner: UNT Libraries Government Documents Department

Measurement of the B0 ->&#960&#8722&#8467&#957and B ->&#951(&#8242)&#8467&#957Branching Fractions, the B0 ->&#960&#8722&#8467&#957and B ->&#951&#8467&#957Form-Factor Shapes, and Determination of |Vub|

Description: We report the results of a study of the exclusive charmless semileptonic decays, B{sup +} {yields} {eta}{sup {prime}}{ell}{sup +}{nu} and B{sup 0} {yields} {pi}{sup -}{ell}{sup +}{nu}, undertaken with approximately 464 million B{bar B} pairs collected at the {Upsilon}(4S) resonance with the BABAR detector. The analysis uses events in which the signal B decays are reconstructed with a loose neutrino reconstruction technique. We obtain partial branching fractions for B{sup +} {yields} {eta}{ell}{sup +}{nu} and B{sup 0} {yields} {pi}{sup -}{ell}{sup +}{nu} decays in three and 12 bins of q{sup 2}, respectively, from which we extract the f{sub +}(q{sup 2}) form-factor shapes and the total branching fractions {Beta}(B{sup +} {yields} {eta}{ell}{sup +}{nu}) = (0.36 {+-} 0.05{sub stat} {+-} 0.04{sub syst}) x 10{sup -4} and {Beta}(B{sup 0} {yields} {pi}{sup -}{ell}{sup +}{nu}) = (1.42 {+-} 0.05{sub stat} {+-} 0.07{sub syst}) x 10{sup -4}. We also measure {Beta}(B{sup +} {yields} {eta}{sup {prime}}{ell}{sup +}{nu}) = (0.24 {+-} 0.08{sub stat} {+-} 0.03{sub syst}) x 10{sup -4}. We obtain values for the magnitude of the CKM matrix element |V{sub ub}| using three different QCD calculations.
Date: August 12, 2011
Creator: del Amo Sanchez, P.; Lees, J.P.; Poireau, V.; Prencipe, E.; Tisserand, V.; /Annecy, LAPP et al.
Partner: UNT Libraries Government Documents Department