J. Ilic

Observation of B-0 -> K-*0(K)over-bar(*0) and search for B-0 -> K-*0(K)over-bar(*0)

We report the observation of the b-->d penguin-dominated decay B;{0}-->K;{*0}K[over ];{*0} with a sample of 383.2+/-4.2 million BB[over ] pairs collected with the BABAR detector at the PEP-II asymmetric-energy e;{+}e;{-} collider at the Stanford Linear Accelerator Center. The measured branching fraction is B(B;{0}-->K;{*0}K[over ];{*0})=[1.28_{-0.30};{+0.35}+/-0.11]x10;{-6} and the fraction of longitudinal polarization is f_{L}(B;{0}-->K;{*0}K[over ];{*0})=0.80_{-0.12};{+0.10}+/-0.06. The first error quoted is statistical and the second systematic. We also obtain an upper limit at the 90% confidence level on the branching fraction for B(B;{0}-->K;{*0}K;{*0})<0.41x10;{-6}.

Search for b -> u transitions in B-->[K+pi(-)pi(0)](D)K-

We search for decays of a B meson into a neutral D meson and a charged kaon, with the D meson decaying into a charged kaon, a charged pion, and a neutral pion. This final state can be reached through the b→c transition B-→D0K- followed by the doubly Cabibbo-suppressed D0→K+π-π0, or the b→u transition B-→D 0K- followed by the Cabibbo-favored D 0→K+π-π0. The interference of these two amplitudes is sensitive to the angle γ of the unitarity triangle. We present results based on 226×106 e+e-→Υ(4S)→BB events collected with the BABAR detector at SLAC. We find no significant evidence for these decays and we set a limit RADS≡Γ([K+π-π0]DK-)+Γ([K-π+π0]DK+)/Γ([K+π-π0]DK+)+Γ([K-π+π0]DK-)<0.039 at 95% confidence level, which we translate with a Bayesian approach into rB≡|A(B-→D 0K-)/A(B-→D0K-)|<0.19 at 95% confidence level.

Extracting longitudinal shower development information from crystal calorimetry plus tracking

arXiv:0711.1593v2 [physics.ins-det] 11 Apr 2008 Extracting longitudinal shower development information from crystal calorimetry plus tracking D.N. Brown a , J. Ilic b , G.B. Mohanty b a Lawrence b Department Berkeley National Laboratory, Berkeley, California 94720, USA of Physics, University of Warwick, Coventry CV4 7AL, United Kingdom Abstract We present an approach to derive longitudinal shower development information from the longitudinally unsegmented B A B AR electromagnetic calorimeter by using tracking information. Our algorithm takes advantage of the good three- dimensional tracking resolution of B A B AR , which provides an independent geometric constraint on the shower as measured in the B A B AR crystal calorimeter. We show that adding the derived longitudinal shower development information to standard particle identification algorithms significantly improves the low-momentum separation of pions from electrons and muons. We also verify that the energy dependence of the electromagnetic shower development we measure is consistent with the prediction of a standard electromagnetic shower model. Key words: Particle Identification, Longitudinal Shower Depth, Electromagnetic Calorimetry, Tracking PACS: 29.40.Gx, 29.40.Vj, 07.05.Kf 1. Introduction In present-day nuclear and particle physics ex- periments, inorganic scintillating crystals, such as NaI(Tl) and CsI(Tl), are often used to construct electromagnetic calorimeters when a precise mea- surement of the energy is required [1]. Crystal calorimeters can be finely segmented in the dimen- sion transverse to the shower development without sacrificing energy resolution, thus providing a good measurement of the lateral shower development. However, engineering and energy resolution consid- erations prevent finely segmenting crystal calorime- ters along the direction of shower development. Both lateral and longitudinal shower development information are useful in charged particle identi- Email addresses: Dave Brown@lbl.gov (D.N. Brown), J.Ilic@warwick.ac.uk (J. Ilic), G.B.Mohanty@warwick.ac.uk (G.B. Mohanty). Preprint submitted to Elsevier Science fication (PID) algorithms, particularly in electron identification. Because crystal calorimeters cannot provide direct longitudinal shower development in- formation, they lose an important input to particle identification. In this paper, we present a technique in which longitudinal shower development information is indirectly extracted from a longitudinally unseg- mented crystal calorimeter in conjunction with a precise tracking system. This technique was devel- oped for use with the B A B AR [2] detector, but it can be applied at any detector which combines crystal calorimetry and precision tracking. It exploits the fact that B A B AR has a tracking system capable of precisely determining the three-dimensional trajec- tory of charged particles, and the fact that these trajectories are not in general collinear with the crystal axes. A similar algorithm has previously been used for sampling calorimeters with fine lateral segmentation [3]. 11 April 2008

Observation of the semileptonic decays B -> D(*)tau(-)(nu)over-bar(tau) and evidence for B -> D tau(-)(nu)over-bar(tau)

We present measurements of the semileptonic decays B--->D0tau-nutau, B--->D*0tau-nutau, B0-->D+tau-nutau, and B0-->D*+tau-nutau, which are potentially sensitive to non-standard model amplitudes. The data sample comprises 232x10(6) Upsilon(4S)-->BB decays collected with the BABAR detector. From a combined fit to B- and B0 channels, we obtain the branching fractions B(B-->Dtau-nutau)=(0.86+/-0.24+/-0.11+/-0.06)% and B(B-->D*tau-nutau)=(1.62+/-0.31+/-0.10+/-0.05)% (normalized for the B0), where the uncertainties are statistical, systematic, and normalization-mode-related.

Time-dependent Dalitz plot analysis of B-0 ->(DK0)-K--/+pi(+/-) decays

We present for the first time a measurement of the weak phase 2β+γ obtained from a time-dependent Dalitz plot analysis of B0→D K0π± decays. Using a sample of approximately 347×106 BB pairs collected by the BABAR detector at the PEP-II asymmetric-energy storage rings and assuming the ratio r of the b→u and b→c decay amplitudes to be 0.3, we obtain 2β+γ=(83±53±20)° and the equivalent solution at +180°. The magnitudes and phases for the resonances associated with the b→c transitions are also extracted from the fit.

Measurements of the branching fractions of B-0 ->(KK+K-)-K-*0, B-0 -> K-*0 pi K-+(-), B-0 ->(KK+)-K-*0 pi(-), and B-0 -> K-*0 pi(+)pi(-)

Branching fraction measurements of charmless B0→K*0h1+h2- (h1,2=K, π) decays are presented, using a data sample of 383×106 Υ(4S)→BB decays collected with the BABAR detector at the PEP-II asymmetric-energy B-meson factory at SLAC. The results are B(B0→K*0K+K-)=(27.5±1.3±2.2)×10-6, B(B0→K*0π+K-)=(4.6±1.1±0.8)×10-6, and B(B0→K*0π+π-)=(54.5±2.9±4.3)×10-6. The first errors quoted are statistical and the second are systematic. An upper limit is set for B(B0→K*0K+π-)<2.2×10-6 at 90% confidence level. We also present measurements of CP-violating asymmetries for the observed decays.