Search results for "FLAVOUR"
showing 10 items of 310 documents
Accidental stability of dark matter
2013
We propose that dark matter is stable as a consequence of an accidental Z(2) that results from a flavour symmetry group which is the double-cover group of the symmetry group of one of the regular geometric solids. Although model-dependent, the phenomenology resembles that of a generic >inert Higgs> dark matter scheme.
Lepton-flavour violation in hadronic tau decays and μ-τ conversion in nuclei
2021
Within the Standard Model Effective Field Theory framework, with operators up to dimension 6, we perform a model-independent analysis of the lepton-flavour-violating processes involving tau leptons. Namely, we study hadronic tau decays and $\ell$--$\tau$ conversion in nuclei, with $\ell = e,\mu$. Based on available experimental limits, we establish constraints on the Wilson coefficients of the operators contributing to these processes. Our work paves the way to extract the related information from Belle II and foreseen future experiments.
Disentangling new physics contributions in lepton flavour violating τ decays
2016
Abstract The possibility to discriminate between different operators contributing to lepton flavour violating tau decays is discussed within an effective field theory framework. Correlations among decay rates in different channels as well as differential distributions in many-body decays are considered. Recent developments in the determination of the hadronic form factors for τ → l π π ( l = e , μ ) decays are incorporated in the analysis. The above issues are exemplified by considering a Higgs-like boson with lepton flavour violating couplings. Implications of the search for lepton flavour violating Higgs decays performed recently by the CMS collaboration are also discussed.
$\Lambda_b^0$-baryon production in pp collisions in the general-mass variable-flavour-number scheme and comparison with CMS and LHCb data
2018
We calculate the next-to-leading-order cross section for the inclusive production of $\Lambda_b$ baryons in pp collisions in the general-mass variable-flavor-number scheme. We use realistic evolved non-perturbative fragmentation functions obtained from fits to B-meson production in $e^+ e^-$ annihilation and compare our results for transverse-momentum and rapidity distributions with recent experimental data from the CMS and the LHCb collaborations at the CERN LHC. We find satisfactory agreement in general, with some indication for the need to modify the available fragmentation functions at larger values of the scale variable.
Invariant approach to flavor-dependent CP-violating phases in the MSSM
2004
We use a new weak basis invariant approach to classify all the observable phases in any extension of the Standard Model (SM). We apply this formalism to determine the invariant CP phases in a simplified version of the Minimal Supersymmetric SM with only three non-trivial flavour structures. We propose four experimental measures to fix completely all the observable phases in the model. After these phases have been determined from experiment, we are able to make predictions on any other CP-violating observable in the theory, much in the same way as in the Standard Model all CP-violation observables are proportional to the Jarlskog invariant.
Flavor violation in supersymmetric SU(5) GUT at large tan beta
2001
We study flavor violation in the general SUSY SU(5) GUT assuming all the third generation Yukawa couplings to be due to the renormalizable physics above GUT scale. At large tan beta, as suggested by Yukawa unification in SU(5), sizable flavor violation in the left (right) slepton (down squark) sector can be induced in nonminimal models due to renormalization effects of down type Yukawa couplings between GUT and Planck scales, in addition to the flavor violation in the right slepton sector. The new flavor physics contribution to K-(K) over bar, B-(B) over bar mixing is small but might be of phenomenological interest in the case of b --> s gamma. The sign of the latter contribution is the sam…
Flavour-violating charged lepton decays in seesaw-type models
1994
Analytic expressions of lepton-flavour- and lepton-number-violating decays of charged leptons are derived in the context of general $SU(2)_L\otimes U(1)_Y$ seesaw scenarios that are motivated by grand unified theories (GUT's) or superstring models, in which left-handed and/or right-handed neutral singlets are present. Possible constraints imposed by cosmology and low-energy data are briefly discussed. The violation of the decoupling theorem in flavour-dependent graphs due to the presence of heavy neutral leptons of Dirac or Majorana nature is emphasized. Numerical estimates reveal that the decays $\tau^-\to e^-e^-e^+$ or $\tau^-\to e^-\mu^-\mu^+$ can be as large as $\sim 10^{-6}$, which may…
Indirect CP violation in the B-system
1997
We show that, contrary to the flavour mixing amplitude q/p, both Re(epsilon) and Im(epsilon) are observable quantities, where epsilon is the phase- convention-independent CP mixing. We consider semileptonic B_d decays from a CP tag and build appropriate time-dependent asymmetries to separate out Re(epsilon) and Im(epsilon). "Indirect" CP violation would have in Im(epsilon)/(1+|epsilon|^2) its most prominent manifestation in the B-system, with expected values in the standard model ranging from -0.37 to -0.18. This quantity is controlled by a new observable phase: the relative one between the CP-violating and CP-conserving parts of the effective hamiltonian. For time-integrated rates we point…
Correlated neutral B meson decays into CP eigenstates
2003
In the two correlated $B$ meson decay experiment we propose to measure intensities relating CP eigenstate ($J/\psi K_{S,L}$) decays on $both$ sides, which will be measurable in future upgrades of KEK and PEP. As a CP-forbidden transition, we obtain $I(J/\psi K_S, J/\psi K_S, \Delta t) \sim \sin ^2 (2\beta)$. We calculate in a model independent way all the possible intensities relating final CP and flavour eigenstate decays. Under CPT-invariance, the asymmetries for processes related by CP$\Delta t$ vanish for $\Delta \Gamma =0$ and measure $\Delta \Gamma$ linearly. We notice the impossibility to isolate the sign of $\cos (2\bet a)$ without an independent knowledge of the sign of $\Delta \Ga…
Minimal flavour seesaw models
2009
26 pages, 8 figures.-- ArXiv pre-print available at: http://arxiv.org/abs/0906.1461