2,802 research outputs found
Precision test of the SM with Kl2 and Kl3 decays at KLOE
Kaon decay studies seeking new-physics (NP) effects in leptonic (K_l2) or
semileptonic (K_l3) decays are discussed.
A unitarity test of the first row of the CKM mixing matrix is obtained from
the KLOE precision measurements of Kl3 widths for K^+-, K_L, and (unique to
KLOE) K_S, complemented with the absolute branching ratio for the K_mu2 decay.
KLOE results lead to constraints for NP models and can probe possible charged
Higgs exchange contribution in SM extensions with two Higgs doublets.
The main focus in the present document is set on a new measurement of
R_K=Gamma(K_e2)/Gamma(K_mu2) with an accuracy at the % level, aiming at finding
evidence of deviations from the SM prediction induced by lepton-flavor
violation NP effects.Comment: Contributed to Rencontres de Moriond EW 2009, La Thuile, Italy, 7-14
March 200
The rare decay B --> X_s l^+ l^- to NNLL precision for arbitrary dilepton invariant mass
We present a new phenomenological analysis of the inclusive rare decay . In particular, we present the first calculation of the NNLL
contributions due to the leading two-loop matrix elements, evaluated for
arbitrary dilepton invariant mass. This allows to obtain the first NNLL
estimates of the dilepton mass spectrum and the lepton forward-backward
asymmetry in the high region, and to provide an
independent check of previously published results in the low region. The numerical impact of these NNLL corrections in the
high-mass region () amounts to -13% in the
integrated rate, and leads to a reduction of the scale uncertainty to .
The impact of non-perturbative contributions in this region is also discussed
in detail.Comment: 40 pages, 12 figures. v2: extended phenomenological discussion;
results unchanged; published versio
Higgs-Mediated tau -> 3 mu in the Supersymmetric Seesaw Model
Recent observations of neutrino oscillations imply non-zero neutrino masses
and flavor violation in the lepton sector, most economically explained by the
seesaw mechanism. Within the context of supersymmetry, lepton flavor violation
(LFV) among the neutrinos can be communicated by renormalization group flow to
the sleptons and from there to the charged leptons. We show that LFV can appear
in the couplings of the neutral Higgs bosons, an effect that is strongly
enhanced at large tan(beta). In particular, we calculate the branching fraction
for tau -> 3 mu and mu -> 3 e mediated by Higgs and find that they can be as
large as 10^{-7} and 5x10^{-14} respectively. These modes, along with B^0 -> mu
mu, can provide important evidence for supersymmetry before direct discovery of
supersymmetric partners occurs. Along with tau -> mu gamma and mu -> e gamma,
they can also provide key insights into the form of the neutrino Yukawa mass
matrix.Comment: 9 pages LaTeX, 2 figures. Added a discussion of mu -> 3e and its
ramifications for probing neutrino mass matrix. Also added references, fixed
typos, and made one notational chang
New NNLL Results on the Decay B --> X(s) L+ L-
We present here new NNLL predictions on the inclusive rare decay B --> X(S)
L+ L- based on our new two-loop QCD analysis of the four-quark operators.Comment: typo in (1) fixed, input parameters slightly change
Kaon physics with a high-intensity proton driver
We study opportunities for future high-precision experiments in kaon physics
using a high-intensity proton driver, which could be part of the front-end of a
muon storage ring complex. We discuss in particular the rare decays
, , , and
lepton-flavour violating modes such as and . The
outstanding physics potential and long-term interest of these modes is
emphasized. We review status and prospects of current and planned experiments
for the processes under consideration, and indicate possible improvements and
strategies towards achieving the necessary higher sensitivity. Finally, we
outline the machine requirements needed to perform these high-precision kaon
experiments in the context of a muon storage ring facility.Comment: 26 pages, 12 figures; report of the kaon physics working group for
the ECFA studies on neutrino factory and muon storage rings at CERN, G.
Buchalla (convener); references update
Physics Opportunities with the FCC-hh Injectors
In this chapter we explore a few examples of physics opportunities using the
existing chain of accelerators at CERN, including potential upgrades. In this
context the LHC ring is also considered as a part of the injector system. The
objective is to find examples that constitute sensitive probes of New Physics
that ideally cannot be done elsewhere or can be done significantly better at
theCERN accelerator complex. Some of these physics opportunities may require a
more flexible injector complex with additional functionality than that just
needed to inject protons into the FCC-hh at the right energy, intensity and
bunch structure. Therefore it is timely to discuss these options concurrently
with the conceptual design of the FCC-hh injector system.Comment: 13 pages, chapter 5 in Physics at the FCC-hh, a 100 TeV pp collide
Strong rescattering in K-> 3pi decays and low-energy meson dynamics
We present a consistent analysis of final state interactions in
decays in the framework of Chiral Perturbation Theory.
The result is that the kinematical dependence of the rescattering phases cannot
be neglected. The possibility of extracting the phase shifts from future
interference experiments is also analyzed.Comment: 14 pages in RevTex, 3 figures in postscrip
On B_s -> mu+ mu- and Cold Dark Matter Scattering in the MSSM with Non-Universal Higgs Masses
We show that present experimental constraints on B_s -> mu+ mu- decay and the
CDMS upper limit on the cold dark matter elastic scattering cross section
already have significant impact on the parameter space of the minimal
supersymmetric extension of the Standard Model (MSSM) with non-universal
supersymmetry-breaking scalar masses for the Higgs multiplets (NUHM). The
relaxation of scalar universality in the MSSM allows the possibility of a
relatively light mass M_A for the pseudoscalar Higgs boson. The present upper
limit on B_s -> mu+ mu- already excludes much of the scope for this possibility
in the NUHM, in contrast to the constrained MSSM with universal scalar masses
(CMSSM), where B_s -> mu+ mu- decay does not exclude any ranges of parameters
not already excluded by b -> s \gamma decay. Cold dark matter scattering is
also enhanced for small M_A, but the impact of present upper limit on B_s ->
mu+ mu- on the NUHM parameter space is in many cases greater than that of the
CDMS scattering limit, particularly at large tanb.Comment: 17 pages, 14 eps figure
Higgs-Mediated tau --> mu and tau --> e transitions in II Higgs doublet Model and Supersymmetry
We study the phenomenology of the mu-tau and e-tau lepton flavour violation
(LFV) in a general two Higgs Doublet Model (2HDM) including the supersymmetric
case. We consider several LFV decay modes of the charged fermion tau, namely
tau-> l_jgamma, tau->l_j l_k l_k and tau-> l_jeta. The predictions and the
correlations among the rates of the above processes are computed. In
particular, it is shown that tau->l_jgamma processes are the most sensitive
channels to Higgs-mediated LFV specially if the splitting among the neutral
Higgs bosons masses is not below the 10% level.Comment: v2=published version: 13 pages, 4 figures, text improved and
reference added. Two loop effects (relevant for tau->l_jgamma) added.
Conclusions unchange
Implications on SUSY breaking mediation mechanisms from observing and the muon
We consider and the muon in various SUSY
breaking mediation mechanisms. If the decay is observed
at Tevatron Run II with a branching ratio larger than ,
the noscale supergravity (including the gaugino mediation), the gauge mediation
scenario with small number of messenger fields and low messenger scale, and a
class of anomaly mediation scenarios will be excluded, even if they can
accommodate a large muon . On the other hand, the minimal
supergravity scenario and similar mechanisms derived from string models can
accommodate this observation.Comment: 4 pages, 3 figure
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