4,485 research outputs found

### Inelastic Dark Matter and the SABRE Experiment

We present here the sensitivity of the SABRE (Sodium iodide with Active
Background REjection) experiment to benchmark proto-philic, spin dependent,
Inelastic Dark Matter models previously proposed due to their lowered tension
with existing experimental results. We perform fits to cross section, mass, and
mass splitting values to find the best fit to DAMA/LIBRA data for these models.
In this analysis, we consider the Standard Halo Model (SHM), as well as an
interesting extension upon it, the SHM+Stream distribution, to investigate the
influence of the Dark Matter velocity distribution upon experimental
sensitivity and whether or not its consideration may be able to help relieve
the present experimental tension. Based on our analysis, SABRE should be
sensitive to all the three benchmark models within 3-5 years of data taking.Comment: Adjusted for full DAMA run 1+2 efficiency. Updated to match published
versio

### Probing new physics in electroweak penguins through B_d and B_s decays

An enhanced electroweak penguin amplitude due to the presence of unknown new
physics can explain the discrepancies found between theory and experiment in
the B -> pi K decays, in particular in A_CP(B^- -> pi^0 K^-) - A_CP(\bar{B}^0
-> pi^+ K^-), but the current precision of the theoretical and experimental
results does not allow to draw a firm conclusion. We argue that the \bar{B}_s
-> phi rho^0 and \bar{B}_s -> phi pi^0 decays offer an additional tool to
investigate this possibility. These purely isospin-violating decays are
dominated by electroweak penguins and we show that in presence of a new physics
contribution their branching ratio can be enhanced by about an order of
magnitude, without violating any constraints from other hadronic B decays. This
makes them very interesting modes for LHCb and future B factories. In
arXiv:1011.6319 we have performed both a model-independent analysis and a study
within realistic New Physics models such as a modified-Z^0-penguin scenario, a
model with an additional Z' boson and the MSSM. In this article we summarise
the most important results of our study.Comment: 8 pages, 5 figures, LaTeX. Talk given at Discrete2010, Rome, 6-11
December 2010; References adde

### Why do we need higher order fully exclusive Monte Carlo generator for Higgs boson production from heavy quark fusion at LHC?

In this paper we argue that having available higher order fully exclusive
Monte Carlo generator for Higgs boson production from heavy quark fusion will
be mandatory for data analysis at LHC. The H to tau tau channel, a key for
early discovery of the Higgs boson in the MSSM scenario, is discussed. With
simplified example and for mH = 120 GeV we show, that depending on choice among
presently available approaches, used for simulation of Higgs boson production
from b bbar H Yukawa coupling, final acceptance for the signal events being
reconstructed inside mass window may differ by a factor of 3. The spread is
even larger (up to a factor of 10) for other production mechanisms (promising
for some regions of the MSSM parameter space). The complete analysis, which
necessarily will add stringent requirements for background rejection (such as
identification of b-jet or veto on b-jet) and which will require statistical
combination of samples selected with different selection criteria may only
enhance the uncertainty.Comment: 14 pages, 22 figure

### CP asymmetries at D0

Using two independent measurements of the semileptonic CP asymmetry in the
$B_s$ system, we constrain the CP violating phase of the $B_s$ system to be
$\phi_s = -0.70^{+0.47}_{-0.39}$. The data sample corresponds to an integrated
luminosity of 1.1 fb$^{-1}$ accumulated with D0 detector at the Fermilab
Tevatron collider. We also measure the direct CP violating asymmetry in the
decay $B^+ \to J/\psi K^+$ to be $A_{CP}(B^+ \to J/\psi K^+) = +0.0067 \pm
0.0074$(stat)$\pm0.0026$(syst). The data corresponds to an integrated
luminosity of 1.6 fb$^{-1}$.Comment: contributed paper to EPS07, Manchester, UK, manuscript number
EPSHEPP17

### QCD Approach to B->D \pi Decays and CP Violation

The branching ratios and CP violations of the $B\to D\pi$ decays, including
both the color-allowed and the color-suppressed modes, are investigated in
detail within QCD framework by considering all diagrams which lead to three
effective currents of two quarks. An intrinsic mass scale as a dynamical gluon
mass is introduced to treat the infrared divergence caused by the soft
collinear approximation in the endpoint regions, and the Cutkosky rule is
adopted to deal with a physical-region singularity of the on mass-shell quark
propagators. When the dynamical gluon mass $\mu_g$ is regarded as a universal
scale, it is extracted to be around $\mu_g = 440$ MeV from one of the
well-measured $B\to D\pi$ decay modes. The resulting predictions for all
branching ratios are in agreement with the current experimental measurements.
As these decays have no penguin contributions, there are no direct $CP$
asymmetries. Due to interference between the Cabibbo-suppressed and the
Cabibbo-favored amplitudes, mixing-induced CP violations are predicted in the
$B\to D^{\pm}\pi^{\mp}$ decays to be consistent with the experimental data at
1-$\sigma$ level. More precise measurements will be helpful to extract weak
angle $2\beta+\gamma$.Comment: 21pages,5 figures,3 tables, typos corrected and numerical result for
one of decay channels is improve

### CPV tests with rare kaon decays

The K_S \to pi+/- e+ e- decay mode has been investigated using the data
collected in 2002 by the NA48/1 collaboration. With about 23k signal events and
59k K_L \to pi+ pi- pi0_D normalization decays, the K_S \to pi+ pi- e+ e-
branching ratio was determined. This result is also used to set an upper limit
on the presence of E1 direct emission in the decay amplitude. The CP-violating
asymmetry has been also measured.
We report on measurements of the rare decays K +/- \to pi+/- e+ e- and K+/-
\to pi+/- mu+ mu- . The full NA48/2 data set was analyzed, leading to more than
7200 reconstructed events in the electronic and more than 3000 events in the
muonic channel, the latter exceeding the total existing statistics by a factor
of four. For both channels the selected events are almost background-free. From
these events, we have determined the branching fraction and form factors of
K+/- \to pi+/- e+ e- using different theoretical models. Our results improve
the existing world averages significantly. In addition, we measured the CP
violating asymmetry between K+ and K- in this channel to be less than a few
percent.Comment: 4 pages, 1 figure, To appear in the proceedings of IX International
Conference on Hyperons, Charm and Beauty Hadrons (BEACH2010), Perugia, Italy,
21-26 June 201

### Bremsstrahlung simulation in K to pi l^pm nu_l (gamma) decays

In physics simulation chains, the PHOTOS Monte Carlo program is often used to
simulate QED effects in decays of intermediate particles and resonances. The
program is based on an exact multiphoton phase space. In general, the matrix
element is obtained from iterations of a universal kernel and approximations
are involved. To evaluate the program precision, it is necessary to formulate
and implement within the generator the exact matrix element, which depends on
the decay channel. Then, all terms necessary for non-leading logarithms are
taken into account.
In the present letter we focus on the decay K to pi l^pm nu_l and tests of
the PHOTOS Monte Carlo program. We conclude a 0.2% relative precision in the
implementation of the hard photon matrix element into the emission kernel,
including the case where approximations are used.Comment: 1+20 pages, 8 figure

### Analysis of $B \to a_1(1260)(b_1(1235))K^*$ decays in the perturbative QCD approach

Within the framework of perturbative QCD approach, we study the charmless
two-body decays $B\to a_1(1260)K^*, b_1(1235)K^*$. Using the decays constants
and the light-cone distribution amplitudes for these mesons derived from the
QCD sum rule method, we find the following results: (a) Our predictions for the
branching ratios are consistent well with the QCDF results within errors, but
much larger than the naive factorization approach calculation values. (b) We
predict that the anomalous polarizations occurring in the decays $B\to \phi
K^*, \rho K^*$ also happen in the decays $B\to a_1K^*$, while do not happen in
the decays $B\to b_1K^*$. Here the contributions from the annihilation diagrams
play an important role to explain the lager transverse polarizations in the
decays $B\to a_1K^*$, while they are not sensitive to the polarizations in
decays $B\to b_1K^*$. (c) Our predictions for the direct CP-asymmetries agree
well with the QCDF results within errors. The decays $\bar B^0\to
b^{+}_1K^{*-}, B^-\to b^{0}_1K^{*-}$ have larger direct CP-asymmetries, which
could be measured by the present LHCb experiments.Comment: 12pages, 1figures. arXiv admin note: substantial text overlap with
arXiv:1203.5913, arXiv:1203.591

- …