1,377 research outputs found
Search for new physics in and
Transitions of the type are flavour changing neutral
current processes where new physics can enter in competing loop diagrams with
respect to the Standard Model contributions. In these decays several
observables sensitive to new physics, and where theoretical uncertainties are
under control, can be constructed. Particularly interesting are the angular
asymmetries in the decay and the measurement of the
branching fraction of the decays . Recent measurements
of these observables and the measurement of the isospin asymmetry in the decays
are presented.Comment: Presented at Flavor Physics and CP Violation (FPCP 2012), Hefei,
China, May 21-25, 201
A new relation between the zero of in and the anomaly in
We present two exact relations, valid for any dilepton invariant mass region
(large and low-recoil) and independent of any effective Hamiltonian
computation, between the observables and of the angular
distribution of the 4-body decay . These relations
emerge out of the symmetries of the angular distribution. We discuss the
implications of these relations under the (testable) hypotheses of no scalar or
tensor contributions and no New Physics weak phases in the Wilson coefficients.
Under these hypotheses there is a direct relation among the observables
, and . This can be used as an independent
consistency test of the measurements of the angular observables. Alternatively,
these relations can be applied directly in the fit to data, reducing the number
of free parameters in the fit. This opens up the possibility to perform a full
angular fit of the observables with existing datasets. An important consequence
of the found relations is that a priori two different measurements, namely the
measured position of the zero () of the forward-backward asymmetry
and the value of evaluated at this same point, are
related by . Under the hypotheses of real
Wilson coefficients and being SM-like, we show that the higher the
position of the smaller should be the value of evaluated
at the same point. A precise determination of the position of the zero of
together with a measurement of (and ) at this
position can be used as an independent experimental test of the anomaly in
. We also point out the existence of upper and lower bounds for
, namely , which
constraints the physical region of the observables.Comment: 5 pages, 3 figure
Search for New Physics in SHiP and at future colliders
SHiP is a newly proposed fixed-target experiment at the CERN SPS with the aim
of searching for hidden particles that interact very weakly with SM particles.
The work presented in this document investigates SHiP's physics reach in the
parameter space of the Neutrino Minimal Standard Model (MSM), which is a
theory that could solve most problems left open by the Standard Model with
sterile neutrinos. A model introducing an extra symmetry in the hidden
sector, providing a natural candidate for dark matter, is also explored. This
work shows that the SHiP experiment can improve by several orders of magnitude
the sensitivity to Heavy Neutral Leptons below 2 GeV, scanning a large part of
the parameter space below the meson mass. The remainder of the MSM
parameter space, dominated by right-handed neutrinos with masses above 2 GeV,
can be explored at a future collider. Similarly, SHiP can greatly
improve present constraints on dark photons.Comment: Proceedings for the INFIERI 2014 schoo
Towards establishing Lepton Flavour Universality violation in decays
Rare semileptonic transitions provide some of the
most promising frameworks to search for new physics effects. Recent analyses of
these decays have indicated an anomalous behaviour in measurements of angular
distributions of the decay and
lepton-flavour-universality observables. Unambiguously establishing if these
deviations have a common nature is of paramount importance in order to
understand the observed pattern. We propose a novel approach to independently
and complementary probe this hypothesis by performing a simultaneous amplitude
analysis of and decays. This method enables the direct determination of
observables that encode potential non-equal couplings of muons and electrons,
and are found to be insensitive to nonperturbative QCD effects. If current
hints of new physics are confirmed, our approach could allow an early discovery
of physics beyond the standard model with LHCb run II data sets.Comment: 6 pages, 7 figures. Matching the journal versio
A simple and fast exact clustering algorithm defined for complex networks and based on the properties of primes
In this paper a new clustering method based on primes is proposed. This method define a nodes cluster of any complex network, considering the nodes with same input/output number and same number of paths with equal length, so all the network nodes with analogous functions will be possible to identify. The clustering algorithm proposed, results very efficient because it is defined on simple computations with primes. For example, with our algorithm the analysis of a network with 500 nodes and 124750 connections is performed in 80 seconds on Pentium 4 with CPU 2Ghz and 1Gb ram. Keywords: Complex network, clustering method, graph theory, unidirectional/bidirectional network, complete path
A significant minimization of Pearson’s X2 statistics in 2x2 contingency tables: preliminary results for small samples
The Pearson’s chi-square test or X2 test represents a nonparametric test more used in Medicine, Biology and Social Sciences, but it introduces some error for 2x2 contingency tables, therefore Yates introduces a continuity correction. This correction produces a very conservative result of X2 statistics with overestimation of p-value and consequently a type II error is very likely. The goal of this paper is to define, with a statistical approach, a significant minimization of Pearson’s X2 statistics for small data sample, based on concept of arithmetic mean, that could be a possible efficient statistic for reducing the type II error in the calculation of p-value
the at LHC
The ATLAS, CMS and LHCb experiments will perform extensive searches for
physics Beyond the Standard Model (BSM). The investigation of decays of beauty
hadrons represents an alternative and complementary approach to the direct BSM
searches. A particularly promising observable for the search of New Physics
(NP) in hadron decays, is the measurement of the branching ratio of the
decay . This observable is sensitive to physics BSM
with new scalar or pseudoscalar effective operators, such as theories involving
an extended Higgs sector. Here the prospects of the ATLAS, CMS and the LHCb
experiments for such a measurement are discussed. In particular the LHCb
experiment, thanks to its good particle identification and momentum resolution,
has the potential for an early discovery of this decay.Comment: Proceeding of the CKM 2010 worksho
Tests of Factorization and SU(3) Relations in B Decays into Heavy-Light Final States
Using data from the B factories and the Tevatron, we perform tests of how
well non-leptonic B decays of the kind B -> D^{(*)}_{(s)} P, where P is a pion
or kaon, are described within the factorization framework. We find that
factorization works well - as is theoretically expected - for color-allowed,
tree-diagram-like topologies. Moreover, also exchange topologies, which have a
non-factorizable character, do not show any anomalous behavior. We discuss also
isospin triangles between the B -> D^{(*)} pi decay amplitudes, and determine
the corresponding amplitudes in the complex plane, which show a significant
enhancement of the color-suppressed tree contribution with respect to the
factorization picture. Using data for B -> D^{(*)} K decays, we determine
SU(3)-breaking effects and cannot resolve any non-factorizable SU(3)-breaking
corrections larger than \sim 5%. In view of these results, we point out that a
comparison between the \bar B^0_d -> D^+\pi^- and \bar B^0_s -> D_s^+\pi^-
decays offers an interesting new determination of f_d/f_s. Using CDF data, we
obtain the most precise value of this ratio at CDF, and discuss the prospects
for a corresponding measurement at LHCb.Comment: 12 pages, 6 figures, matches published version in Physical Review
Extracting Angular Observables without a Likelihood and Applications to Rare Decays
Our goal is to obtain a complete set of angular observables arising in a
generic multi-body process. We show how this can be achieved without the need
to carry out a likelihood fit of the angular distribution to the measured
events. Instead, we apply the method of moments that relies both on the
orthogonality of angular functions and the estimation of integrals by Monte
Carlo techniques. The big advantage of this method is that the joint
distribution of all observables can be easily extracted, even for very few
events. The method of moments is shown to be robust against mismodeling of the
angular distribution. Our main result is an explicit algorithm that accounts
for systematic uncertainties from detector-resolution and acceptance effects.
Finally, we present the necessary process-dependent formulae needed for direct
application of the method to several rare decays of interest.Comment: 13 pages, 4 figure
zfit: scalable pythonic fitting
Statistical modeling is a key element in many scientific fields and
especially in High-Energy Physics (HEP) analysis. The standard framework to
perform this task in HEP is the C++ ROOT/RooFit toolkit; with Python bindings
that are only loosely integrated into the scientific Python ecosystem. In this
paper, zfit, a new alternative to RooFit written in pure Python, is presented.
Most of all, zfit provides a well defined high-level API and workflow for
advanced model building and fitting, together with an implementation on top of
TensorFlow, allowing a transparent usage of CPUs and GPUs. It is designed to be
extendable in a very simple fashion, allowing the usage of cutting-edge
developments from the scientific Python ecosystem in a transparent way. The
main features of zfit are introduced, and its extension to data analysis,
especially in the context of HEP experiments, is discussed.Comment: 12 pages, 2 figure
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