9,861 research outputs found
Tau Physics from B Factories
Some recent -physics results are presented from the BaBar and Belle
experiments at the SLAC and KEK B factories, which produce copious numbers of
-lepton pairs. Measurements of the tau mass and lifetime allow to test
lepton universality and CPT invariance, while searches for lepton-flavour
violation in tau decays are powerful ways to look for physics beyond the
Standard Model. In semihadronic, non-strange tau decays, the vector hadronic
final state is particularly important in helping determine the hadronic
corrections to the anomalous magnetic moment of the muon, while studies of
strange final states are the best available ways to measure the CKM matrix
element and the mass of the strange quark.Comment: Presented at Charm 2006, International Workshop on Tau-Charm Physics,
June 05-07 2006, Beijing, Chin
Graded Hecke algebras for disconnected reductive groups
We introduce graded Hecke algebras H based on a (possibly disconnected)
complex reductive group G and a cuspidal local system L on a unipotent orbit of
a Levi subgroup M of G. These generalize the graded Hecke algebras defined and
investigated by Lusztig for connected G.
We develop the representation theory of the algebras H. obtaining complete
and canonical parametrizations of the irreducible, the irreducible tempered and
the discrete series representations. All the modules are constructed in terms
of perverse sheaves and equivariant homology, relying on work of Lusztig. The
parameters come directly from the data (G,M,L) and they are closely related to
Langlands parameters.
Our main motivation for considering these graded Hecke algebras is that the
space of irreducible H-representations is canonically in bijection with a
certain set of "logarithms" of enhanced L-parameters. Therefore we expect these
algebras to play a role in the local Langlands program. We will make their
relation with the local Langlands correspondence, which goes via affine Hecke
algebras, precise in a sequel to this paper.Comment: Theorem 3.4 and Proposition 3.22 in version 1 were not entirely
correct as stated. This is repaired in a new appendi
Multichannel calculation of the very narrow and the very broad
The narrow (2317) and broad (2300-2400) charmed
scalar mesons and their radial excitations are described in a coupled-channel
quark model that also reproduces the properties of the light scalar nonet. All
two-meson channels containing ground-state pseudoscalars and vectors are
included. The parameters are chosen fixed at published values, except for the
overall coupling constant , which is fine-tuned to reproduce the
(2317) mass, and a damping constant for subthreshold
contributions. Variations of and (2300-2400) pole
postions are studied for different values. Calculated cross sections
for -wave and scattering, as well as resonance pole positions,
are given for the value of that fits the light scalars. The thus
predicted radially excited state (2850), with a width of about 50
MeV, seems to have been observed already.Comment: 3 pages, EPJ LaTeX, 2 Postscript figures, 1 table; parallel talk at
the IVth International Conference on Quarks and Nuclear Physics (QNP06),
Madrid, 5-10 June 200
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
Penguin Mediated B Decays at BABAR
We report on preliminary results of searches for penguin mediated B decays based on 20.7 fb^{-1} of data collected at the Y(4S) peak with the BABAR detector at PEP-II. The following branching fractions have been measured: BR(B+ --> phi K+) = (7.7^{+1.6}_{-1.4} +- 0.8)*10^{-6}, BR(B0 --> phi K0) = (8.1^{+3.1}_{-2.5} +- 0.8)*10^{-6}, BR(B+ --> phi K*+) = (9.7^{+4.2}_{-3.4} +- 1.7)*10^{-6}, BR(B0 --> phi K*0) = (8.7^{+2.5}_{-2.1} +- 1.1)*10^{-6}, BR(B+--> omega pi+) = (6.6^{+2.1}_{-1.8} +- 0.7)*10^{-6}, BR(B --> eta K^*0) = (19.8^{+6.5}_{-5.6} +-1.7)*10^{-6}, where the first error is statistical and the second systematic. For several other modes we report upper limits on their branching fractions; for example for the following flavor-changing neutral current decays, BR(B--> K l+ l-) K* l+ l-) < 2.5*10^{-6}, at 90% Confidence Level (C.L.)
Understanding the newly observed Y(4008) by Belle
Very recently a new enhancement around 4.05 GeV was observed by Belle
experiment. In this short note, we discuss some possible assignments for this
enhancement, i.e. and molecular state. In these two
assignments, Y(4008) can decay into with comparable
branching ratio with that of . Thus one suggests
high energy experimentalists to look for Y(4008) in channel.
Furthermore one proposes further experiments to search missing channel
, and especially and
, which will be helpful to distinguish and
molecular state assignments for this new enhancement.Comment: 4 pages, 5 figures. Typos correcte
Radiative and Semileptonic B Decays Involving Higher K-Resonances in the Final States
We study the radiative and semileptonic B decays involving a spin-
resonant with parity for and for
in the final state. Using the large energy effective theory (LEET)
techniques, we formulate transition form factors in the large
recoil region in terms of two independent LEET functions
and , the values of
which at zero momentum transfer are estimated in the BSW model. According to
the QCD counting rules, exhibit a dipole
dependence in . We predict the decay rates for ,
and . The
branching fractions for these decays with higher -resonances in the final
state are suppressed due to the smaller phase spaces and the smaller values of
. Furthermore, if the spin of
becomes larger, the branching fractions will be further suppressed due to the
smaller Clebsch-Gordan coefficients defined by the polarization tensors of the
. We also calculate the forward backward asymmetry of the decay, for which the zero is highly insensitive to the
-resonances in the LEET parametrization.Comment: 27 pages, 4 figures, 7 tables;contents and figures corrected, title
and references revise
Charmless Hadronic B-Meson Decays
We give an overview of the experimental measurements and the theoretical
understanding of the branching fractions and CP-violating asymmetries of
charmless B-meson decays. Most experimetal results are from the BABAR and Belle
experiments during the past decade. The global features of these experimental
results are typically well described by the QCD-motivated theories such as QCD
factorization, pQCD and soft-collinear effective theory. The agreement between
theory and experiment is generally satisfactory, though there remain some
unsolved puzzles that pose a great challenge to both theorists and
experimentalists.Comment: 33 pages, 11 figures, 1 table, invited review to appear in Ann. Rev.
of Nucl. and Part. Scienc
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