7,600 research outputs found
An Improved Standard Model Prediction Of BR(B -> tau nu) And Its Implications For New Physics
The recently measured B -> tau nu branching ratio allows to test the Standard
Model by probing virtual effects of new heavy particles, such as a charged
Higgs boson. The accuracy of the test is currently limited by the experimental
error on BR(B -> tau nu) and by the uncertainty on the parameters fB and |Vub|.
The redundancy of the Unitarity Triangle fit allows to reduce the error on
these parameters and thus to perform a more precise test of the Standard Model.
Using the current experimental inputs, we obtain BR(B -> tau nu)_SM = (0.84 +-
0.11)x10^{-4}, to be compared with BR(B -> tau nu)_exp = (1.73 +-
0.34)x10^{-4}. The Standard Model prediction can be modified by New Physics
effects in the decay amplitude as well as in the Unitarity Triangle fit. We
discuss how to disentangle the two possible contributions in the case of
minimal flavour violation at large tan beta and generic loop-mediated New
Physics. We also consider two specific models with minimal flavour violation:
the Type-II Two Higgs Doublet Model and the Minimal Supersymmetric Standard
Model.Comment: 7 pages, 13 figures, 1 table. v2: added references and discussion of
B -> D tau nu in the 2HDM. v3: added Bs->mumu in the 2HDM. Final version to
appear in PL
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
Spectrum for Heavy Quankonia and Mixture of the Relevant Wave Functions within the Framework of Bethe-Salpeter Equation
Considering the fact that some excited states of the heavy quarkonia
(charmonium and bottomonium) still missing in experimental observations and
potential applications of the relevant wave functions of the bound states, we
re-analyze the spectrum and the relevant wave functions of the heavy quarkonia
within the framework of Bethe-Salpeter (B.S.) equation with a proper
QCD-inspired kernel. Such a kernel for the heavy quarkonia, relating to
potential of non-relativistic quark model, is instantaneous, so we call the
corresponding B.S. equation as BS-In equation throughout the paper.
Particularly, a new way to solve the B.S. equation, which is different from the
traditional ones, is proposed here, and with it not only the known spectrum for
the heavy quarkonia is re-generated, but also an important issue is brought in,
i.e., the obtained solutions of the equation `automatically' include the
'fine', 'hyperfine' splittings and the wave function mixture, such as
wave mixing in states, wave mixing in
states for charmonium and bottomonium etc. It is pointed out that the best
place to test the wave mixture probably is at -factory ( collider
running at -boson pole with extremely high luminosity).Comment: 26 pages, 8 figure
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
Recent developments in radiative B decays
We report on recent theoretical progress in radiative B decays. We focus on a
calculation of logarithmically enhanced QED corrections to the branching ratio
and forward-backward asymmetry in the inclusive rare decay anti-B --> X(s) l+
l-, and present the results of a detailed phenomenological analysis. We also
report on the calculation of NNLO QCD corrections to the inclusive decay anti-B
--> X(s) gamma. As far as exclusive modes are concerned we consider
transversity amplitudes and the impact of right-handed currents in the
exclusive anti-B --> K^* l+ l- decay. Finally, we state results for exclusive B
--> V gamma decays, notably the time-dependent CP-asymmetry in the exclusive B
--> K^* gamma decay and its potential to serve as a so-called ``null test'' of
the Standard Model, and the extraction of CKM and unitarity triangle parameters
from B --> (rho,omega) gamma and B --> K^* gamma decays.Comment: 5 pages, 2 figures. Accepted for publication in the proceedings of
International Europhysics Conference on High Energy Physics (EPS-HEP2007),
Manchester, England, 19-25 Jul 200
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
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