8,134 research outputs found
The UTfit Collaboration Average of D meson mixing data: Spring 2012
We derive constraints on the parameters , and
that describe meson mixing using all available data, allowing
for CP violation. We also provide posterior distributions and predictions for
observable parameters appearing in physics.Comment: 5 pages, 3 figure
Correlated neutral B meson decays into CP eigenstates
In the two correlated meson decay experiment we propose to measure
intensities relating CP eigenstate () decays on sides,
which will be measurable in future upgrades of KEK and PEP. As a CP-forbidden
transition, we obtain . We calculate in a model independent way all the possible intensities
relating final CP and flavour eigenstate decays. Under CPT-invariance, the
asymmetries for processes related by CP vanish for
and measure linearly. We notice the impossibility to isolate
the sign of \cos (2\bet a) without an independent knowledge of the sign of
. This exhaustion of the possible Golden Plate and flavour
decays provides new observables which may throw light in our present
understanding of CKM physics.Comment: 9 pages, no figures. Minor changes to coincide with published PLB
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Measurement of branching fractions and CP-violating charge asymmetries for B-meson decays to D^(*)D^(*), and implications for the Cabibbo-Kobayashi-Maskawa angle Îł
We present measurements of the branching fractions and charge asymmetries of B decays to all D^(*)D^(*) modes. Using 232Ă10^6 BB pairs recorded on the ΄(4S) resonance by the BABAR detector at the e^+e^- asymmetric B factory PEP-II at the Stanford Linear Accelerator Center, we measure the branching fractions B(B^0âD^(*+)D^(*-))=(8.1±0.6±1.0)Ă10^(-4), B(B^0âD^(*±)D^â)=(5.7±0.7±0.7)Ă10^(-4), B(B^0âD^+D^-)=(2.8±0.4±0.5)Ă10^(-4), B(B^+âD^(*+)D^(*0))=(8.1±1.2±1.2)Ă10^(-4), B(B^+âD^*+D^0)=(3.6±0.5±0.4)Ă10^(-4), B(B^+âD^+D^(*0))=(6.3±1.4±1.0)Ă10^(-4), and B(B^+âD^+D^(0))=(3.8±0.6±0.5)Ă10^(-4), where in each case the first uncertainty is statistical and the second systematic. We also determine the limits B(B^0âD^(*0)D^(*0))<0.9Ă10^(-4), B(B^0âD^(*0)D^0)<2.9Ă10^(-4), and B(B^0âD^0D^0)<0.6Ă10^(-4), each at 90% confidence level. All decays above denote either member of a charge-conjugate pair. We also determine the CP-violating charge asymmetries A(B^0âD^(*±)D^â)=0.03±0.10±0.02, A(B^+âD^(*+)D^(*0))=-0.15±0.11±0.02, A(B^+âD^(*+)D^0)=-0.06±0.13±0.02, A(B^+âD^+D^(*0))=0.13±0.18±0.04, and A(B^+âD^+D^0)=-0.13±0.14±0.02. Additionally, when we combine these results with information from time-dependent CP asymmetries in B^0âD^((*)+)D^((*)-) decays and world-averaged branching fractions of B decays to D_s^(*)D^(*) modes, we find the Cabibbo-Kobayashi-Maskawa phase Îł is favored to lie in the range (0.07â2.77) radians (with a +0 or +Ï radians ambiguity) at 68% confidence level
Search for the decay Ï-â3Ï^-2Ï^+2Ï^0Îœ_Ï
A search for the decay of the Ï lepton to five charged and two neutral pions is performed using data collected by the BABAR detector at the PEP-II asymmetric-energy e^+e^- collider. The analysis uses 232ââfb^(-1) of data at center-of-mass energies on or near the ΄(4S) resonance. We observe 10 events with an expected background of 6.5_(-1.4)^(+2.0) events. In the absence of a signal, we set the limit on the branching ratio B(Ï-â3Ï^-2Ï^+2Ï^0Îœ_Ï)<3.4Ă10^(-6) at the 90% confidence level. This is a significant improvement over the previously established limit. In addition, we search for the decay mode Ï-â2ÏÏ-Îœ_Ï. We observe 1 event with an expected background of 0.4+1.0/-0.4 events and calculate the upper limit B(Ï-â2ÏÏ-Îœ_Ï)<5.4Ă10^(-7) at the 90% confidence level. This is the first upper limit for this mode
Study of the decay B^0âD^(*+)ÏÏ^-
We report on a study of the decay B^0âD^(*+)ÏÏ^- with the BABAR detector at the PEP-II B-factory at the Stanford Linear Accelerator Center. Based on a sample of 232Ă10^6 BB decays, we measure the branching fraction B(B^0âD^(*+)ÏÏ^-)=(2.88±0.21(stat.)±0.31(syst.))Ă10^(-3). We study the invariant mass spectrum of the ÏÏ^- system in this decay. This spectrum is in good agreement with expectations based on factorization and the measured spectrum in Ï-âÏÏ-Îœ_Ï. We also measure the polarization of the D^(*+) as a function of the ÏÏ^- mass. In the mass region 1.1 to 1.9 GeV we measure the fraction of longitudinal polarization of the D^(*+) to be ÎL/Î=0.654±0.042(stat.)±0.016(syst.). This is in agreement with the expectations from heavy-quark effective theory and factorization assuming that the decay proceeds as B^(-0)âD^(*+)Ï(1450)-, Ï(1450)^-âÏÏ^-
Search for the charmed pentaquark candidate Î_c(3100)^0 in e^+e^- annihilations at âs=10.58ââGeV
We search for the charmed pentaquark candidate reported by the H1 collaboration, the Î_c(3100)^0, in e^+e^- interactions at a center-of-mass (c.m.) energy of 10.58 GeV, using 124ââfb^(-1) of data recorded with the BABAR detector at the PEP-II e^+e^- facility at SLAC. We find no evidence for such a state in the same pD^(*-) decay mode reported by H1, and we set limits on its production cross section times branching fraction into pD^(*-) as a function of c.m. momentum. The corresponding limit on its total rate per e^+e^-âqq event, times branching fraction, is about 3 orders of magnitude lower than rates measured for the charmed Î_c and ÎŁ_c baryons in such events
Observation of B^0 Meson Decay to a_1^±(1260)Ï^â
We present a measurement of the branching fraction of the decay B^0âa_1^±(1260)Ï^â with a_1^±(1260)âÏ^âÏ^±Ï^±. The data sample corresponds to 218Ă10^6 BB pairs produced in e^+e^- annihilation through the ΄(4S) resonance. We measure the branching fraction B(B^0âa_1^±(1260)Ï^â)B(a_1^±(1260)âÏ^âÏ^±Ï^±)=(16.6±1.9±1.5)Ă10^(-6), where the first error quoted is statistical and the second is systematic
Measurements of branching fractions, rate asymmetries, and angular distributions in the rare decays BâKâ^+â^- and BâK^*â^+â^-
We present measurements of the flavor-changing neutral current decays BâKâ^+â^- and BâK^*â^+â^-, where â^+â^- is either an e^+e^- or ÎŒ^+ÎŒ^- pair. The data sample comprises 229Ă10^6ââ΄(4S)âBB decays collected with the BABAR detector at the PEP-II e^+e^- storage ring. Flavor-changing neutral current decays are highly suppressed in the standard model and their predicted properties could be significantly modified by new physics at the electroweak scale. We measure the branching fractions B(BâKâ^+â^-)=(0.34±0.07±0.02)Ă10^(-6), B(BâK^*â^+â^-)=(0.78-0.17^(+0.19)±0.11)Ă10^(-6), the direct CP asymmetries of these decays, and the relative abundances of decays to electrons and muons. For two regions in â^+â^- mass, above and below m_(J/Ï), we measure partial branching fractions and the forward-backward angular asymmetry of the lepton pair. In these same regions we also measure the K^* longitudinal polarization in BâK^*â^+â^- decays. Upper limits are obtained for the lepton-flavor-violating decays BâKeÎŒ and BâK^*eÎŒ. All measurements are consistent with standard model expectation
Inclusive Î_c^+ production in e^+e^- annihilations at âs=10.54ââGeV and in ΄(4S) decays
We present measurements of the total production rates and momentum distributions of the charmed baryon Î_c^+ in e^+e^-âhadrons at a center-of-mass energy of 10.54 GeV and in ΄(4S) decays. In hadronic events at 10.54 GeV, charmed hadrons are almost exclusively leading particles in e^+e^-âcc[overbar] events, allowing direct studies of c-quark fragmentation. We measure a momentum distribution for Î_c^+ baryons that differs significantly from those measured previously for charmed mesons. Comparing with a number of models, we find none that can describe the distribution completely. We measure an average scaled momentum of =0.574±0.009 and a total rate of N_(Îc)^(qq[overbar]) =0.057±0.002(exp)±0.015(BF)ââÎ_c^+ per hadronic event, where the experimental error is much smaller than that due to the branching fraction into the reconstructed decay mode, pK^-Ï^+. In ΄(4S) decays we measure a total rate of N_(Îc)^΄=0.091±0.006(exp)±0.024(BF) per ΄(4S) decay, and find a much softer momentum distribution than expected from B decays into a Î_c^+ plus an antinucleon and one to three pions
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