Papers by Alberto Lusiani
Determination of |Vus| from the tau lepton branching fractions
Measurement of Tau Lepton Lifetime from ALEPH
The Albuquerque Meeting Vol 2, 1995
Observation of B0→K*0K¯*0 and Search for B0→K*0K*0
Physical Review Letters, 2008
We report the observation of the b--&... more 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}.
Measurement of D^{0}-D[over ¯]^{0} Mixing Parameters Using D^{0}→K_{S}^{0}π^{+}π^{-} and D^{0}→K_{S}^{0}K^{+}K^{-} Decays
Physical Review Letters, 2010
We report a direct measurement of D0-D0 mixing parameters through a time-dependent amplitude anal... more We report a direct measurement of D0-D0 mixing parameters through a time-dependent amplitude analysis of the Dalitz plots of D(0) → K(S)(0) π+ π- and, for the first time, D0 → K(S)(0)K+ K- decays. The low-momentum pion π(s)(+) in the decay D*+ → D0 π(s)(+) identifies the flavor of the neutral D meson at its production. Using 468.5 fb(-1) of e+ e- colliding-beam data recorded near square root(s)=10.6 GeV by the BABAR detector at the PEP-II asymmetric-energy collider at SLAC, we measure the mixing parameters x = [1.6 ± 2.3(stat) ± 1.2(syst) ± 0.8(model)] × 10(-3), and y = [5.7 ± 2.0(stat) ± 1.3(syst) ± 0.7(model)] × 10(-3). These results provide the best measurement to date of x and y. The knowledge of the value of x, in particular, is crucial for understanding the origin of mixing.
Zeitschrift f�r Physik C Particles and Fields, 1996
From the 64492 selected -pair events, produced at the Z 0 resonance, the measurement of the tau d... more From the 64492 selected -pair events, produced at the Z 0 resonance, the measurement of the tau decays into hadrons from a global analysis using 1991, 1992 and 1993 ALEPH data is presented. Special emphasis is given to the reconstruction of photons, 0 's and the removal of fake photons. A complete and consistent description of the tau hadronic decays is presented, where up to 17 exclusive modes are measured. The new level of precision reached allows a more stringent test of universality in hadronic decays and more accurate measurements of the vector and axial-vector contributions to the total hadronic width.
Physical Review D, 2012
ABSTRACT We present branching fraction measurements for the decays ${B}^{0}\ensuremath{\rightarro... more ABSTRACT We present branching fraction measurements for the decays ${B}^{0}\ensuremath{\rightarrow}{\ensuremath{\rho}}^{0}{K}^{*0}$, ${B}^{0}\ensuremath{\rightarrow}{f}_{0}{K}^{*0}$, and ${B}^{0}\ensuremath{\rightarrow}{\ensuremath{\rho}}^{\ensuremath{-}}{K}^{*+}$, where ${K}^{*}$ is an $S$-wave $(K\ensuremath{\pi}{)}_{0}^{*}$ or a ${K}^{*}(892)$ meson; we also measure ${B}^{0}\ensuremath{\rightarrow}{f}_{0}{K}_{2}^{*}(1430{)}^{0}$. For the ${K}^{*}(892)$ channels, we report measurements of longitudinal polarization fractions (for $\ensuremath{\rho}$ final states) and direct $CP$ violation asymmetries. These results are obtained from a sample of $(471.0\ifmmode\pm\else\textpm\fi{}2.8)\ifmmode\times\else\texttimes\fi{}{10}^{6}$ $B\overline{B}$ pairs collected with the BABAR detector at the PEP-II asymmetric-energy ${e}^{+}{e}^{\ensuremath{-}}$ collider at the SLAC National Accelerator Laboratory. We observe ${\ensuremath{\rho}}^{0}{K}^{*}(892{)}^{0}$, ${\ensuremath{\rho}}^{0}(K\ensuremath{\pi}{)}_{0}^{*0}$, ${f}_{0}{K}^{*}(892{)}^{0}$, and ${\ensuremath{\rho}}^{\ensuremath{-}}{K}^{*}(892{)}^{+}$ with greater than $5\ensuremath{\sigma}$ significance, including systematics. We report first evidence for ${f}_{0}(K\ensuremath{\pi}{)}_{0}^{*0}$ and ${f}_{0}{K}_{2}^{*}(1430{)}^{0}$, and place an upper limit on ${\ensuremath{\rho}}^{\ensuremath{-}}(K\ensuremath{\pi}{)}_{0}^{*+}$. Our results in the ${K}^{*}(892)$ channels are consistent with no direct $CP$ violation.
Physical Review D, 2007
We present updated measurements of the branching fractions and CP asymmetries for B0--&am... more We present updated measurements of the branching fractions and CP asymmetries for B0-->pi0pi0, B±-->pi±pi0, and B±-->K±pi0. Based on a sample of 383×106 Upsilon(4S)-->BB¯ decays collected by the BABAR detector at the PEP-II asymmetric-energy B factory at SLAC, we measure B(B0-->pi0pi0)=(1.47±0.25±0.12)×10-6, B(B±-->pi±pi0)=(5.02±0.46±0.29)×10-6, and B(B±-->K±pi0)=(13.6±0.6±0.7)×10-6. We also measure the CP asymmetries Cpi0pi0=-0.49±0.35±0.05, Api±pi0=0.03±0.08±0.01, and AK±pi0=0.030±0.039±0.010. Finally, we present bounds on the Cabibbo-Kobayashi-Maskawa
Physical Review Letters, 2008
We perform a measurement of the CP asymmetry in b → sγ decays using a sample of 383 × 10 6 BB eve... more We perform a measurement of the CP asymmetry in b → sγ decays using a sample of 383 × 10 6 BB events collected by the BABAR detector at the PEP-II asymmetric B factory. We reconstruct sixteen flavor-specific B decay modes containing a high-energy photon and a hadronic system Xs containing an s quark. We measure the CP asymmetry to be −0.011 ± 0.030(stat) ± 0.014(syst) for a hadronic system mass between 0.6 and 2.8 GeV/c 2 .
Search for B(+)->tau(+)nu decays with hadronic B tags
Physical Review D, 2008
011107-3 completely reconstructed tag B in a hadronic decay mode (Bÿ! D 0Xÿ), and examine the res... more 011107-3 completely reconstructed tag B in a hadronic decay mode (Bÿ! D 0Xÿ), and examine the rest of the event to search for a B! decay. We identify the lepton in the following modes:! e,!,!, and! 0. We find a 2: 2 excess in data and measure a branching fraction of BB! 1: 8 0: 9 ÿ0: 8 stat: 0: 4 bkg: syst: 0: 2 other syst: 10ÿ4. We calculate the product of the B meson decay constant fB and jVubj to be fB jVubj 10: 1 2: 3 ÿ2: 5 stat: 1: 2 ÿ1: 5 syst:
Physical review letters, Jan 30, 2005
We study initial-state radiation events, e+ e- --> gammaISR pi+ pi- J/psi, with data collected... more We study initial-state radiation events, e+ e- --> gammaISR pi+ pi- J/psi, with data collected with the BABAR detector. We observe an accumulation of events near 4.26 GeV/c2 in the invariant-mass spectrum of pi+ pi- J/psi. Fits to the mass spectrum indicate that a broad resonance with a mass of about 4.26 GeV/c2 is required to describe the observed structure. The presence of additional narrow resonances cannot be excluded. The fitted width of the broad resonance is 50 to 90 MeV/c2, depending on the fit hypothesis.
Physics Reports, 1998
Previously published and as yet unpublished QCD results obtained with the ALEPH detector at LEP1 ... more Previously published and as yet unpublished QCD results obtained with the ALEPH detector at LEP1 are presented. The unprecedented statistics allows detailed studies of both perturbative and non-perturbative aspects of strong interactions to be carried out using hadronic Z and tau decays. The studies presented include precise determinations of the strong coupling constant, tests of its avour independence, tests of the SU(3) gauge structure of QCD, study of coherence eects, and measurements of single-particle inclusive distributions and two-particle correlations for many identied baryons and mesons.
Physics Letters B, 1993
The branching fraction of Z ! bb relative to all hadronic decays of the Z has been measured using... more The branching fraction of Z ! bb relative to all hadronic decays of the Z has been measured using event shape variables to preferentially select Z ! bb events. The method chosen applies a combination of shape discriminators and the selection of high transverse momentum leptons to event hemispheres. From a sample of 440,000 hadronic Z decays collected with the ALEPH detector at LEP, the ratio b b = had = 0:228 0:005(stat:) 0:005(syst:) is measured.
Physics Letters B, 1997
In June 1996, the LEP centre-of-mass energy was raised to 161 GeV. Pair production of W bosons in... more In June 1996, the LEP centre-of-mass energy was raised to 161 GeV. Pair production of W bosons in e + e collisions was observed for the first time by the LEP experiments. An integrated luminosity of 11 pb 1 was recorded in the ALEPH detector, in which WW candidate events were observed. In 6 events both Ws decay leptonically. In 16 events, one W decays leptonically, the other into hadrons. In the channel where both Ws decay into hadrons, a signal was separated from the large background by means of several multi-variate analyses. The W pair cross-section is measured to be WW = 4 : 23 0:73stat: 0:19syst: pb:
Physics Letters B, 1997
ALEPH's published measurement of R b = (Z ! b b)= (Z ! hadrons) using a lifetime tag is updated u... more ALEPH's published measurement of R b = (Z ! b b)= (Z ! hadrons) using a lifetime tag is updated using the full LEP 1 data sample. Considerable eort has been devoted to understanding systematic eects. Charm background is better controlled by combining the lifetime tag with a tag based on the b/c hadron mass dierence. Furthermore, the algorithm used to reconstruct the event primary vertex is designed so as to reduce correlations between the two hemispheres of an event.
Physics Letters B, 1998
The data collected by ALEPH at LEP at centre-of-mass energies ranging from 181 to 184 GeV, corres... more The data collected by ALEPH at LEP at centre-of-mass energies ranging from 181 to 184 GeV, corresponding to an integrated luminosity o f 5 7 p b 1 , are analysed to search for pair-produced neutral Higgs bosons h and A, in the b bb b and + b
Physics Letters B, 2001
Searches for pair production of squarks, sleptons, charginos and neutralinos are performed with t... more Searches for pair production of squarks, sleptons, charginos and neutralinos are performed with the data collected by the ALEPH detector at LEP at centre-of-mass energies from 188.6 to 201.6 GeV. No evidence for any such signals is observed in a total integrated luminosity of about 410 pb −1 . The negative results of the searches are translated into exclusion domains in the space of the relevant MSSM parameters, which improve significantly on the constraints set previously. Under the assumptions of gaugino and sfermion mass unification, these results allow a 95% C.L. lower limit of 37 GeV/c 2 to be set on the mass of the lightest neutralino for any tan β and sfermion mass. Additional constraints in the MSSM parameter space are derived from the negative results of ALEPH searches for Higgs bosons. The results are also interpreted in the framework of minimal supergravity.
Physics Letters B, 1998
Starting from a sample of four million hadronic Z decays collected with the ALEPH detector at LEP... more Starting from a sample of four million hadronic Z decays collected with the ALEPH detector at LEP, 404 charged and neutral B mesons are fully reconstructed and used to look for resonant structure in the Bsystem. An excess of events is observed above the expected background in the Bmass spectrum at a mass 5:7 GeV/c 2 , consistent with the production and decay to B of the B states predicted by Heavy Quark Symmetry (HQS). In the framework of HQS, it is found that the mass of the B 2 state is (5739 + 8 11 (stat) +6 4 (syst)) MeV/c 2 and the relative production rate of the B system is BR ( b!B ! B )=BR(b ! B u;d ) = (31 9(stat) +6 5 (syst))%. In the same sample of B mesons, signicant B c harge-avour correlations are observed, which m a y prove important for tagging the initial B state in future CP violation studies.
Physical Review Letters, 2006
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Papers by Alberto Lusiani