-
[show abstract]
[hide abstract]
ABSTRACT: AlGaN/GaN heterostructure Schottky barrier pho-todetector (PD) with multi-Mg x N y /GaN buffer was proposed and fabricated. Compared with AlGaN/GaN heterostructure PD prepared on conventional low-temperature GaN buffer, it was found that we can reduce dark leakage current by more than three orders of magnitude. It was also found that we can use the multi-Mg x N y /GaN buffer to suppress photoconductance gain, enhance UV-to-visible rejection ratio, reduce noise level and enhance the detectivity. Index Terms—AlGaN/GaN heterostructure, multi-Mg x N y /GaN buffer, Schottky barrier photodetector.
IEEE Sensors Journal ; 9. · 1.52 Impact Factor
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[show abstract]
[hide abstract]
ABSTRACT: AlGaN/GaN heterostructure Schottky barrier pho-todetector (PD) with multi-Mg x N y /GaN buffer was proposed and fabricated. Compared with AlGaN/GaN heterostructure PD prepared on conventional low-temperature GaN buffer, it was found that we can reduce dark leakage current by more than three orders of magnitude. It was also found that we can use the multi-Mg x N y /GaN buffer to suppress photoconductance gain, enhance UV-to-visible rejection ratio, reduce noise level and enhance the detectivity. Index Terms—AlGaN/GaN heterostructure, multi-Mg x N y /GaN buffer, Schottky barrier photodetector.
IEEE Sensors Journal ; 9. · 1.52 Impact Factor
-
B. Aubert,
D. Boutigny,
J.-M. Gaillard,
A. Hicheur,
Y. Karyotakis,
J. P. Lees,
P. Robbe,
V. Tisserand,
A. Palano,
A. Pompili, [......],
F. Di Lodovico,
Y. Pan,
R. Prepost,
I. J. Scott,
S. J. Sekula,
J. H. von Wimmersperg-Toeller, S. L. Wu,
Z. Yu,
T. M. B. Kordich,
H. Neal
[show abstract]
[hide abstract]
ABSTRACT: We present a measurement of time-dependent CP-violating asymmetries in neutral B meson decays collected with the BABAR detector at the PEP-II asymmetric-energy e+e- collider at the Stanford Linear Accelerator Center. The data sample consists of 29.7 fb-1 recorded at the Υ(4S) resonance and 3.9 fb-1 off resonance. One of the neutral B mesons, which are produced in pairs at the Υ(4S), is fully reconstructed in the CP decay modes J/ψKS0, ψ(2S)KS0, χc1KS0, J/ψK*0 (K*0→KS0π0) and J/ψKL0, or in flavor-eigenstate modes involving D(*)π/ρ/a1 and J/ψK*0 (K*0→K+π-). The flavor of the other neutral B meson is tagged at the time of its decay, mainly with the charge of identified leptons and kaons. A neural network tagging algorithm is used to recover events without a clear lepton or kaon tag. The proper time elapsed between the decays is determined by measuring the distance between the decay vertices. Wrong-tag probabilities, the time-difference resolution function, and the B0-B0 oscillation frequency Δmd are measured with a sample of about 6350 fully-reconstructed B0 decays in hadronic flavor-eigenstate modes. A maximum-likelihood fit to this flavor eigenstate sample finds Δmd=0.516±0.016(stat)±0.010(syst)ps-1. The value of the asymmetry amplitude sin2β is determined from a simultaneous maximum-likelihood fit to the time-difference distribution of the flavor-eigenstate sample and about 642 tagged B0 decays in the CP-eigenstate modes. We find sin2β=0.59±0.14(stat)±0.05(syst), demonstrating that CP violation exists in the neutral B meson system. We also determine the value of the CP violation parameter |λ|=0.93±0.09(stat)±0.03(syst), which is consistent with the expectation of |λ|=1 for no direct CP violation.
Physical Review D 02/2013; 66(3). · 4.56 Impact Factor
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BABAR Collaboration,
B Aubert,
D Boutigny,
JM Gaillard,
A Hicheur,
Y Karyotakis,
JP Lees,
P Robbe,
V Tisserand,
A Palano, [......],
F Di Lodovico,
Y Pan,
R Prepost,
IJ Scott,
SJ Sekula,
JH von Wimmersperg-Toeller, S L Wu,
Z Yu,
TMB Kordich,
H Neal
[show abstract]
[hide abstract]
ABSTRACT: We search for direct CP violation in charmless hadronic B decays observed in a sample of about 22.7 million BB̅ pairs collected with the BABAR detector at the SLAC PEP-II asymmetric-energy e+e- collider. We measure the following charge asymmetries: ACP(B±→η′K±)=-0.11±0.11±0.02, ACP(B±→ωπ±)=-0.01 - 0.31 + 0.29±0.03, ACP(B±→φK±)=-0.05±0.20±0.03, ACP(B±→φK*±)=-0.43 - 0.30 + 0.36±0.06, and ACP(B0→φK*0)=0.00±0.27±0.03.
Physical Review D 02/2013; 65(5):051101. · 4.56 Impact Factor
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The Babar Collaboration,
J. P. Lees,
V. Poireau,
V. Tisserand,
E. Grauges,
A. Palano,
G. Eigen,
B. Stugu,
D. N. Brown,
L. T. Kerth, [......],
R. J. Sobie,
N. Tasneem,
T. J. Gershon,
P. F. Harrison,
T. E. Latham,
H. R. Band,
S. Dasu,
Y. Pan,
R. Prepost, S. L. Wu
[show abstract]
[hide abstract]
ABSTRACT: We study the decay
$\bar{B}^{0}\rightarrow\Lambda_{c}^{+}\bar{p}\pi^{+}\pi^{-}$, reconstructing
the \Lambda_{c}^{+} baryon in the $p K^{-}\pi^{+}$ mode, using a data sample of
$467\times 10^{6}$ $B\bar{B}$ pairs collected with the BaBar detector at the
PEP-2 storage rings at SLAC. We measure branching fractions for decays with
intermediate $\Sigma_{c}$ baryons to be ${\cal
B}[\bar{B}^{0}\rightarrow\Sigma_{c}(2455)^{++}\bar{p}\pi^{-}]=(21.3 \pm 1.0 \pm
1.0 \pm 5.5) \times 10^{-5}$, ${\cal
B}[\bar{B}^{0}\rightarrow\Sigma_{c}(2520)^{++}\bar{p}\pi^{-}]=(11.5\pm 1.0 \pm
0.5 \pm 3.0)\times 10^{-5}$, ${\cal
B}[\bar{B}^{0}\rightarrow\Sigma_{c}(2455)^{0}\bar{p}\pi^{+}]=(9.1 \pm 0.7 \pm
0.4 \pm 2.4)\times10^{-5}$, and ${\cal
B}[\bar{B}^{0}\rightarrow\Sigma_{c}(2520)^{0}\bar{p}\pi^{+}]= (2.2 \pm 0.7 \pm
0.1\pm 0.6) \times 10^{-5}$, where the uncertainties are statistical,
systematic, and due to the uncertainty on the
$\Lambda_{c}^{+}\rightarrow\proton\Km\pi^{+}$ branching fraction, respectively.
For decays without $\Sigma_{c}(2455)$ or $\Sigma_{c}(2520)$ resonances, we
measure ${\cal
B}[\bar{B}^{0}\rightarrow\Lambda_{c}^{+}\bar{p}\pi^{+}\pi^{-}]_{\mathrm{non-\Sigma_{c}}}=(79
\pm 4 \pm 4 \pm 20)\times10^{-5}$. The total branching fraction is determined
to be ${\cal
B}[\bar{B}^{0}\rightarrow\Lambda_{c}^{+}\bar{p}\pi^{+}\pi^{-}]_{\mathrm{total}}=(123
\pm 5 \pm 7 \pm 32)\times10^{-5}$. We examine multibody mass combinations in
the resonant three-particle $\Sigma_{c}\bar{p}\pi$ final states and in the
four-particle $\Lambda_{c}^{+}\bar{p}\pi^{+}\pi^{-}$ final state, and observe
different characteristics for the $\bar{p}\pi$ combination in neutral versus
doubly-charged $\Sigma_{c}$ decays.
02/2013;
-
G Aad,
T Abajyan,
B Abbott,
J Abdallah,
S Abdel Khalek,
A A Abdelalim,
O Abdinov,
R Aben,
B Abi,
M Abolins, [......],
S Zimmermann,
M Ziolkowski,
R Zitoun,
L Zivković,
V V Zmouchko,
G Zobernig,
A Zoccoli,
M Zur Nedden,
V Zutshi,
L Zwalinski
[show abstract]
[hide abstract]
ABSTRACT: The ATLAS experiment has observed 1995 Z boson candidates in data corresponding to 0.15 nb^{-1} of integrated luminosity obtained in the 2011 LHC Pb+Pb run at sqrt[s_{NN}]=2.76 TeV. The Z bosons are reconstructed via dielectron and dimuon decay channels, with a background contamination of less than 3%. Results from the two channels are consistent and are combined. Within the statistical and systematic uncertainties, the per-event Z boson yield is proportional to the number of binary collisions estimated by the Glauber model. The elliptic anisotropy of the azimuthal distribution of the Z boson with respect to the event plane is found to be consistent with zero.
Physical Review Letters 01/2013; 110(2):022301. · 7.37 Impact Factor
-
G Aad,
T Abajyan,
B Abbott,
J Abdallah,
S Abdel Khalek,
A A Abdelalim,
O Abdinov,
R Aben,
B Abi,
M Abolins, [......],
S Zimmermann,
M Ziolkowski,
R Zitoun,
L Zivković,
V V Zmouchko,
G Zobernig,
A Zoccoli,
M Zur Nedden,
V Zutshi,
L Zwalinski
[show abstract]
[hide abstract]
ABSTRACT: Results of a search for new phenomena in events with an energetic photon and large missing transverse momentum in proton-proton collisions at sqrt[s]=7 TeV are reported. Data collected by the ATLAS experiment at the LHC corresponding to an integrated luminosity of 4.6 fb^{-1} are used. Good agreement is observed between the data and the standard model predictions. The results are translated into exclusion limits on models with large extra spatial dimensions and on pair production of weakly interacting dark matter candidates.
Physical Review Letters 01/2013; 110(1):011802. · 7.37 Impact Factor
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G Aad,
T Abajyan,
B Abbott,
J Abdallah,
S Abdel Khalek,
A A Abdelalim,
O Abdinov,
R Aben,
B Abi,
M Abolins, [......],
S Zimmermann,
M Ziolkowski,
R Zitoun,
L Zivković,
V V Zmouchko,
G Zobernig,
A Zoccoli,
M Zur Nedden,
V Zutshi,
L Zwalinski
[show abstract]
[hide abstract]
ABSTRACT: This Letter presents a search for magnetic monopoles with the ATLAS detector at the CERN Large Hadron Collider using an integrated luminosity of 2.0 fb^{-1} of pp collisions recorded at a center-of-mass energy of sqrt[s]=7 TeV. No event is found in the signal region, leading to an upper limit on the production cross section at 95% confidence level of 1.6/ϵ fb for Dirac magnetic monopoles with the minimum unit magnetic charge and with mass between 200 GeV and 1500 GeV, where ϵ is the monopole reconstruction efficiency. The efficiency ϵ is high and uniform in the fiducial region given by pseudorapidity |η|<1.37 and transverse kinetic energy 600-700<E^{kin}sinθ<1400 GeV. The minimum value of 700 GeV is for monopoles of mass 200 GeV, whereas the minimum value of 600 GeV is applicable for higher mass monopoles. Therefore, the upper limit on the production cross section at 95% confidence level is 2 fb in this fiducial region. Assuming the kinematic distributions from Drell-Yan pair production of spin-1/2 Dirac magnetic monopoles, the efficiency is in the range 1%-10%, leading to an upper limit on the cross section at 95% confidence level that varies from 145 fb to 16 fb for monopoles with mass between 200 GeV and 1200 GeV. This limit is weaker than the fiducial limit because most of these monopoles lie outside the fiducial region.
Physical Review Letters 12/2012; 109(26):261803. · 7.37 Impact Factor
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BaBar Collaboration,
J. P. Lees,
V. Poireau,
V. Tisserand,
J. Garra Tico,
E. Grauges,
A. Palano,
G. Eigen,
B. Stugu,
D. N. Brown, [......],
R. J. Sobie,
N. Tasneem,
T. J. Gershon,
P. F. Harrison,
T. E. Latham,
H. R. Band,
S. Dasu,
Y. Pan,
R. Prepost, S. L. Wu
[show abstract]
[hide abstract]
ABSTRACT: We report on a search for direct CP asymmetry in the singly
Cabibbo-suppressed decay D+- --> K+ K- pi+- using a data sample of 476 fb-1
accumulated with the BaBar detector running at and just below the Y(4S)
resonance. The CP-violating decay rate asymmetry A_CP is determined to be (0.35
+- 0.30 +- 0.15)%. Model-dependent and model-independent Dalitz plot analysis
techniques are used to search for CP-violating asymmetries in the various
intermediate states.
12/2012;
-
G Aad,
T Abajyan,
B Abbott,
J Abdallah,
S Abdel Khalek,
A A Abdelalim,
O Abdinov,
R Aben,
B Abi,
M Abolins, [......],
S Zimmermann,
M Ziolkowski,
R Zitoun,
L Zivković,
V V Zmouchko,
G Zobernig,
A Zoccoli,
M Zur Nedden,
V Zutshi,
L Zwalinski
[show abstract]
[hide abstract]
ABSTRACT: A search is presented for direct top squark pair production in final states with one isolated electron or muon, jets, and missing transverse momentum in proton-proton collisions at sqrt[s]=7 TeV. The measurement is based on 4.7 fb^{-1} of data collected with the ATLAS detector at the LHC. Each top squark is assumed to decay to a top quark and the lightest supersymmetric particle (LSP). The data are found to be consistent with standard model expectations. Top squark masses between 230 GeV and 440 GeV are excluded with 95% confidence for massless LSPs, and top squark masses around 400 GeV are excluded for LSP masses up to 125 GeV.
Physical Review Letters 11/2012; 109(21):211803. · 7.37 Impact Factor
-
J P Lees,
V Poireau,
V Tisserand,
J Garra Tico,
E Grauges,
A Palano,
G Eigen,
B Stugu,
D N Brown,
L T Kerth, [......],
R J Sobie,
N Tasneem,
T J Gershon,
P F Harrison,
T E Latham,
H R Band,
S Dasu,
Y Pan,
R Prepost, S L Wu
[show abstract]
[hide abstract]
ABSTRACT: Although CP violation in the B meson system has been well established by the B factories, there has been no direct observation of time-reversal violation. The decays of entangled neutral B mesons into definite flavor states (B^{0} or B[over ¯]^{0}), and J/ψK_{L}^{0} or cc[over ¯]K_{S}^{0} final states (referred to as B_{+} or B_{-}), allow comparisons between the probabilities of four pairs of T-conjugated transitions, for example, B[over ¯]^{0}→B_{-} and B_{-}→B[over ¯]^{0}, as a function of the time difference between the two B decays. Using 468×10^{6} BB[over ¯] pairs produced in Υ(4S) decays collected by the BABAR detector at SLAC, we measure T-violating parameters in the time evolution of neutral B mesons, yielding ΔS_{T}^{+}=-1.37±0.14(stat)±0.06(syst) and ΔS_{T}^{-}=1.17±0.18(stat)±0.11(syst). These nonzero results represent the first direct observation of T violation through the exchange of initial and final states in transitions that can only be connected by a T-symmetry transformation.
Physical Review Letters 11/2012; 109(21):211801. · 7.37 Impact Factor
-
G Aad,
T Abajyan,
B Abbott,
J Abdallah,
S Abdel Khalek,
A A Abdelalim,
O Abdinov,
R Aben,
B Abi,
M Abolins, [......],
S Zimmermann,
M Ziolkowski,
R Zitoun,
L Zivković,
V V Zmouchko,
G Zobernig,
A Zoccoli,
M Zur Nedden,
V Zutshi,
L Zwalinski
[show abstract]
[hide abstract]
ABSTRACT: A search for direct pair production of supersymmetric top squarks (t[over ˜]_{1}) is presented, assuming the t[over ˜]_{1} decays into a top quark and the lightest supersymmetric particle, χ[over ˜]_{1}^{0}, and that both top quarks decay to purely hadronic final states. A total of 16 (4) events are observed compared to a predicted standard model background of 13.5_{-3.6}^{+3.7}(4.4_{-1.3}^{+1.7}) events in two signal regions based on ∫Ldt=4.7 fb^{-1} of pp collision data taken at sqrt[s]=7 TeV with the ATLAS detector at the LHC. An exclusion region in the t[over ˜]_{1} versus χ[over ˜]_{1}^{0} mass plane is evaluated: 370<m_{t[over ˜]_{1}}<465 GeV is excluded for m_{χ[over ˜]_{1}^{0}}∼0 GeV while m_{t[over ˜]_{1}}=445 GeV is excluded for m_{χ[over ˜]_{1}^{0}}≤50 GeV.
Physical Review Letters 11/2012; 109(21):211802. · 7.37 Impact Factor
-
J P Lees,
V Poireau,
V Tisserand,
J Garra Tico,
E Grauges,
A Palano,
G Eigen,
B Stugu,
D N Brown,
L T Kerth, [......],
N Tasneem,
T J Gershon,
P F Harrison,
T E Latham,
E M T Puccio,
H R Band,
S Dasu,
Y Pan,
R Prepost, S L Wu
[show abstract]
[hide abstract]
ABSTRACT: The photon spectrum in the inclusive electromagnetic radiative decays of the B meson, B→X_{s}γ plus B→X_{d}γ, is studied using a data sample of (382.8±4.2)×10^{6}Υ(4S)→BB[over ¯] decays collected by the BABAR experiment at SLAC. The spectrum is used to extract the branching fraction B(B→X_{s}γ)=(3.21±0.33)×10^{-4} for E_{γ}>1.8 GeV and the direct CP asymmetry A_{CP}(B→X_{s+d}γ)=0.057±0.063. The effects of detector resolution and Doppler smearing are unfolded to measure the photon energy spectrum in the B meson rest frame.
Physical Review Letters 11/2012; 109(19):191801. · 7.37 Impact Factor
-
J. P. Lees,
V. Poireau,
V. Tisserand,
J. Garra Tico,
E. Grauges,
A. Palano,
G. Eigen,
B. Stugu,
D. N. Brown,
L. T. Kerth, [......],
N. Tasneem,
T. J. Gershon,
P. F. Harrison,
T. E. Latham,
E. M. T. Puccio,
H. R. Band,
S. Dasu,
Y. Pan,
R. Prepost, S. L. Wu
[show abstract]
[hide abstract]
ABSTRACT: We use 429 fb-1 of e+e- collision data collected at the Υ(4S) resonance with the BABAR detector to measure the radiative transition rate of b→sγ with a sum of 38 exclusive final states. The inclusive branching fraction with a minimum photon energy of 1.9 GeV is found to be B(B̅ →Xsγ)=(3.29±0.19±0.48)×10-4 where the first uncertainty is statistical and the second is systematic. We also measure the first and second moments of the photon energy spectrum and extract the best-fit values for the heavy-quark parameters, mb and μπ2, in the kinetic and shape function models.
Phys. Rev. D. 09/2012; 86(5).
-
J P Lees,
V Poireau,
V Tisserand,
J Garra Tico,
E Grauges,
A Palano,
G Eigen,
B Stugu,
D N Brown,
L T Kerth, [......],
R J Sobie,
N Tasneem,
T J Gershon,
P F Harrison,
T E Latham,
H R Band,
S Dasu,
Y Pan,
R Prepost, S L Wu
[show abstract]
[hide abstract]
ABSTRACT: Based on the full BABAR data sample, we report improved measurements of the ratios R(D^{(*)})=B(B[over ¯]→D^{(*)}τ^{-}ν[over ¯]_{τ})/B(B[over ¯]→D^{(*)}ℓ_{ℓ}^{-}ν[over ¯]_{ℓ}), where ℓ is either e or μ. These ratios are sensitive to new physics contributions in the form of a charged Higgs boson. We measure R(D)=0.440±0.058±0.042 and R(D^{*})=0.332±0.024±0.018, which exceed the standard model expectations by 2.0σ and 2.7σ, respectively. Taken together, our results disagree with these expectations at the 3.4σ level. This excess cannot be explained by a charged Higgs boson in the type II two-Higgs-doublet model.
Physical Review Letters 09/2012; 109(10):101802. · 7.37 Impact Factor
-
J. P. Lees,
V. Poireau,
V. Tisserand,
J. Garra Tico,
E. Grauges,
A. Palano,
G. Eigen,
B. Stugu,
D. N. Brown,
L. T. Kerth, [......],
N. Tasneem,
T. J. Gershon,
P. F. Harrison,
T. E. Latham,
E. M. T. Puccio,
H. R. Band,
S. Dasu,
Y. Pan,
R. Prepost, S. L. Wu
[show abstract]
[hide abstract]
ABSTRACT: A precise measurement of the cross section of the process e+e-→π+π-(γ) from threshold to an energy of 3 GeV is obtained with the initial-state radiation (ISR) method using 232 fb-1 of data collected with the BABAR detector at e+e- center-of-mass energies near 10.6 GeV. The ISR luminosity is determined from a study of the leptonic process e+e-→μ+μ-(γ)γISR, which is found to agree with the next-to-leading-order QED prediction to within 1.1%. The cross section for the process e+e-→π+π-(γ) is obtained with a systematic uncertainty of 0.5% in the dominant ρ resonance region. The leading-order hadronic contribution to the muon magnetic anomaly calculated using the measured ππ cross section from threshold to 1.8 GeV is (514.1±2.2(stat)±3.1(syst))×10-10.
Phys. Rev. D. 08/2012; 86(3).
-
J. P. Lees,
V. Poireau,
V. Tisserand,
J. Garra Tico,
E. Grauges,
A. Palano,
G. Eigen,
B. Stugu,
D. N. Brown,
L. T. Kerth, [......],
N. Tasneem,
T. J. Gershon,
P. F. Harrison,
T. E. Latham,
E. M. T. Puccio,
H. R. Band,
S. Dasu,
Y. Pan,
R. Prepost, S. L. Wu
[show abstract]
[hide abstract]
ABSTRACT: In a sample of 471×106 BB̅ events collected with the BABAR detector at the PEP-II e+e- collider we study the rare decays B→K(*)ℓ+ℓ-, where ℓ+ℓ- is either e+e- or μ+μ-. We report results on partial branching fractions and isospin asymmetries in seven bins of dilepton mass-squared. We further present CP and lepton-flavor asymmetries for dilepton masses below and above the J/ψ resonance. We find no evidence for CP or lepton-flavor violation. The partial branching fractions and isospin asymmetries are consistent with the Standard Model predictions and with results from other experiments.
Phys. Rev. D. 08/2012; 86(3).
-
J. P. Lees,
V. Poireau,
V. Tisserand,
J. Garra Tico,
E. Grauges,
M. Martinelli,
D. A. Milanes,
A. Palano,
M. Pappagallo,
G. Eigen, [......],
N. Tasneem,
T. J. Gershon,
P. F. Harrison,
T. E. Latham,
E. M. T. Puccio,
H. R. Band,
S. Dasu,
Y. Pan,
R. Prepost, S. L. Wu
[show abstract]
[hide abstract]
ABSTRACT: We report measurements of partial branching fractions for inclusive charmless semileptonic B decays B̅ →Xuℓν̅ and the determination of the Cabibbo–Kobayashi–Maskawa (CKM) matrix element |Vub|. The analysis is based on a sample of 467×106 Υ(4S)→BB̅ decays recorded with the BABAR detector at the PEP-II e+e- storage rings. We select events in which the decay of one of the B mesons is fully reconstructed and an electron or a muon signals the semileptonic decay of the other B meson. We measure partial branching fractions ΔB in several restricted regions of phase space and determine the CKM element |Vub| based on different QCD predictions. For decays with a charged lepton momentum pℓ*>1.0 GeV in the B meson rest frame, we obtain ΔB=(1.80±0.13stat±0.15sys±0.02theo)×10-3 from a fit to the two-dimensional MX-q2 distribution. Here, MX refers to the invariant mass of the final state hadron X and q2 is the invariant mass squared of the charged lepton and neutrino. From this measurement we extract |Vub|=(4.33±0.24exp±0.15theo)×10-3 as the arithmetic average of four results obtained from four different QCD predictions of the partial rate. We separately determine partial branching fractions for B̅ 0 and B- decays and derive a limit on the isospin breaking in B̅ →Xuℓν̅ decays.
Phys. Rev. D. 08/2012; 86(3).
-
BABAR Collaboration,
J. P. Lees,
V. Poireau,
V. Tisserand,
J. Garra Tico,
E. Grauges,
A. Palano,
G. Eigen,
B. Stugu,
D. N. Brown, [......],
R. J. Sobie,
N. Tasneem,
T. J. Gershon,
P. F. Harrison,
T. E. Latham,
H. R. Band,
S. Dasu,
Y. Pan,
R. Prepost, S. L. Wu
[show abstract]
[hide abstract]
ABSTRACT: We report the results of a study of the exclusive charmless semileptonic
decays, B^0 --> pi^- l^+ nu, B^+ --> pi^0 l^+ nu, B^+ --> omega l^+ nu, B^+ -->
eta l^+ nu and B^+ --> eta^' l^+ nu, (l = e or mu) undertaken with
approximately 462x10^6 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 in several bins of q^2, the square of the momentum
transferred to the lepton-neutrino pair, for B^0 --> pi^- l^+ nu, B^+ --> pi^0
l^+ nu, B^+ --> omega l^+ nu and B^+ --> eta l^+ nu. From these distributions,
we extract the form-factor shapes f_+(q^2) and the total branching fractions
BF(B^0 --> pi^- l^+ nu) = (1.45 +/- 0.04_{stat} +/- 0.06_{syst})x10^-4
(combined pi^- and pi^0 decay channels assuming isospin symmetry), BF(B^+ -->
omega l^+ nu) = (1.19 +/- 0.16_{stat} +/- 0.09_{syst})x10^-4 and BF(B^+ --> eta
l^+ nu) = (0.38 +/- 0.05_{stat} +/- 0.05_{syst})x10^-4. We also measure BF(B^+
--> eta^' l^+ nu) = (0.24 +/- 0.08_{stat} +/- 0.03_{syst})x10^-4. We obtain
values for the magnitude of the CKM matrix element V_{ub} by direct comparison
with three different QCD calculations in restricted q^2 ranges of B --> pi l^+
nu decays. From a simultaneous fit to the experimental data over the full q^2
range and the FNAL/MILC lattice QCD predictions, we obtain |V_{ub}| = (3.25 +/-
0.31)x10^-3, where the error is the combined experimental and theoretical
uncertainty.
08/2012;
-
J. P. Lees,
V. Poireau,
E. Prencipe,
V. Tisserand,
J. Garra Tico,
E. Grauges,
M. Martinelli,
D. A. Milanes,
A. Palano,
M. Pappagallo, [......],
T. J. Gershon,
P. F. Harrison,
T. E. Latham,
E. M. T. Puccio,
H. R. Band,
S. Dasu,
Y. Pan,
R. Prepost,
C. O. Vuosalo, S. L. Wu
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ABSTRACT: We study the processes e+e-→K+K-π+π-γ, K+K-π0π0γ, and K+K-K+K-γ, where the photon is radiated from the initial state. About 84 000, 8000, and 4200 fully reconstructed events, respectively, are selected from 454 fb-1 of BABAR data. The invariant mass of the hadronic final state defines the e+e- center-of-mass energy, so that the K+K-π+π-γ data can be compared with direct measurements of the e+e-→K+K-π+π- reaction. No direct measurements exist for the e+e-→K+K-π0π0 or e+e-→K+K-K+K- reactions, and we present an update of our previous result based on a data sample that is twice as large. Studying the structure of these events, we find contributions from a number of intermediate states and extract their cross sections. In particular, we perform a more detailed study of the e+e-→ϕ(1020)ππγ reaction and confirm the presence of the Y(2175) resonance in the ϕ(1020)f0(980) and K+K-f0(980) modes. In the charmonium region, we observe the J/ψ in all three final states and in several intermediate states, as well as the ψ(2S) in some modes, and measure the corresponding products of branching fraction and electron width.
Phys. Rev. D. 07/2012; 86(1).
