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D. Delepine

Publications and source records attributed to D. Delepine.

At least 37 records · Page 2Linked to original sources
arXiv2007

SUSY R parity violation and CP asymmetry in semi-leptonic tau-decays

We analyze the CP violation in the semileptonic | ΔS|=1 tau-decays in supersymmetric extensions of the standard model (SM) with R parity violating term. We show that the CP asymmetry of tau-decay is enhanced significantly and the current experimental limits obtained by CLEO collaborations can be easily accommodated. We argue that observing CP violation in semi leptonic tau-decay would be a clear evidence for R-parity violating SUSY extension of the SM.

hep-ph↗
arXiv2007

Is there a paradox in CP asymmetries of tau to K_{L,S} pi nu decays?

Based on the description of unstable $K_{L,S}$ particles in quantum field theory (QFT), we compute the time-dependent probabilities for transitions between asymptotic states in $τ^{\pm} \to [π^+π^-]_Kπ^{\pm}ν$ decays, where the pair $[π^+π^-]_K$ is the product of (intermediate state) neutral kaon decays. Then we propose a definition of $τ$ decays into $K_L$ and $K_S$ states, which reflects into the cancellation between their CP rate asymmetries, thus solving in a natural way the paradox pointed out previously in litterature. Since our definition of $K_{L,S}$ final states in $τ$ decays is motivated on experimental grounds, our predictions for the integrated CP rate asymmetries can be tested in a dedicated experiment.

hep-ph↗
arXiv2006

Supersymmetry and CP violation in |ΔS|=1 tau-decays

We compute the SUSY effective hamiltonian that describes the |ΔS|=1 semileptonic decays of tau leptons. We provide analytical expressions for supersymmetric contribution to tau --> u bar{s} nu_{tau} transition in mass insertion approximation. We show that SUSY contributions may enhance the CP asymmetry of tau --> K pi nu_{tau} decays by several orders of magnitude than the standard model expectations. However, the resulting asymmetry is still well below the current experimental limits obtained by CLEO collaborations. We emphasize that measuring CP rate asymmetry in this decay larger than 10^{-6} would be a clear evidence of physics beyond the supersymmetric extensions of the standard model.

hep-ph↗
arXiv2005

CP violation in semileptonic tau lepton decays

The leading order contribution to the direct CP asymmetry in tau^{+/-} -> K^{+/-} pi^0 nu_{tau} decay rates is evaluated within the Standard Model. The weak phase required for CP violation is introduced through an interesting mechanism involving second order weak interactions, which is also responsible for tiny violations of the Delta S= Delta Q rule in K_{l3} decays. The calculated CP asymmetry turns out to be of order 10^{-12}, leaving a large window for studying effects of non-standard sources of CP violation in this observable.

hep-ph↗
arXiv2005

Annihilation contribution and $B\to a_0 π, f_0 K$ decays

We analyze the decays $B^0 \to a^\pm_0 π^\mp$ and $B^{-,0} \to f_0 K^{-,0}$ and show that within the factorization approximation a phenomenological consistent picture can be obtained. We show that in this approach the $O_6$ operator provides the dominant contributions to the suppressed channel $B^0 \to a^+_0 π^-$. When the $a_0$ is considered a two quark state, evaluation of the annihilation form factor using Perturbative $QCD$ implies that this contribution is not negligible, and furthermore it can interfere constructively or destructively with other penguin contributions. As a consequence of this ambiguity, the positive identification of $B^0 \to π^+ a_0^-$ can not distinguish between the two or four quark assignment of the $a_0$. According to our calculation, a best candidate to distinguish the nature of $a_0$ scalar is $Br(B^-\to π^0a_0^-)$ since the predictions for a four quark model is one order of magnitude smaller than for the two quark assignment. When the scalars are seen as two quarks states, simple theoretical assumptions based on SU(2) isospin symmetry provide relations between different B decays involving one scalar and one pseudoscalar meson.

hep-ph↗
arXiv2004

Top flavour violating decays in general supersymmetric models

We analyse the top flavour violating decays in general supersymmetric model using the mass insertion approximation. In particular, we discuss the impact of a light right-handed top-squark and large mixing between the first or second and third generation of up-squarks on processes as t -> q gamma,g . We also take into account the relevant experimental constraints from B-physics and the requirements for a successfull electroweak baryogenesis on squark mixings. We show that for general large mixings in squarks mass matrix, the branching ratio of the t -> q gamma, g (q=u,c) can be as large as 10^{-6}.

hep-ph↗
arXiv2003

Neutrino CP phases and lepton electric dipole moments in supersymmetric theories

We analyse the dependence of the electron electric dipole moment (EDM) on neutrino CP violating phases in the context of supersymmetric models. We start by studying the supersymmetric contributions to the lepton EDM and lepton flavour violation processes tau -> mu gamma and mu -> e gamma, in the framework of the mass insertion approximation, showing that, due to the large neutrino mixing, mu -> e gamma leads to severe constraints on the relevant mass insertions. We derive model independent bounds on these mass insertions and show that once these bounds are satisfied, the present experimental limits on electron EDM do not constraint the neutrino phases.

hep-ph↗
arXiv2002

Flavor-dependent CP violation and electroweak baryogenesis in supersymmetric theories

We analyze electroweak baryogenesis in supersymmetric theories with flavor-dependent CP-violating phases. We generalize the standard approach to include the flavor dependence of the CP-violating sources and obtain an analytical approximate expression for the baryon asymmetry of the universe induced by these sources. It is shown that in the framework where the $μ$-term is real and the chargino sources vanish, large flavor mixing might lead to a substantial baryon asymmetry through the squark contributions, once the condition to have a strong first-order phase transition induced by light right-handed up squarks is relaxed. We derive model independent bounds on the relevant up-squark left-right mass insertions. We show that in supersymmetric models with non-minimal flavor structure these bounds can be reached and the required baryon asymmetry can be generated, while satisfying the constraints coming from the electric dipole moments.

hep-ph↗
arXiv2002

Extra Dimensions, Isosinglet Charged Leptons and Neutrino Factories

Isosinglet fermions naturally arise in a variety of extensions of the Standard Model, in particular in models with extra dimensions. In this paper, we study the effect of the addition of a new isosinglet charged lepton to the standard spectrum, with special emphasis on implications for neutrino asymmetries to be measured at future neutrino factories. Lepton flavour violation in neutral current and lepton universality constraints are extensively discussed. We show that new physics effects in $ν_e-ν_μ$ CP asymmetries are significantly enhanced due to leptonic maximal mixings but still too small to give a signature at future neutrino factories. A signal for CP asymmetries in $ν_μ-ν_τ$ channel due to new physics could be observed at $1-3 σ$ if lepton flavour violating $τ$ decays are seen in a very close future in B-factories like BELLE experiment.

hep-ph↗
arXiv2001

Dynamical CP Violation and Flavour-Changing Processes

We investigate the phenomenological constraints on a model where, besides the standard model Higgs sector, there is an effective new strong interaction acting on the third generation of quarks and characterized by a $θ$-like term. This $θ$ term induces electroweak symmetry breaking and leads to dynamical spontaneous CP violation. We show that the constraints coming from K physics and the electric dipole moment of the neutron impose that the new physics scale should be of the order of 35 TeV. Contrary to naive expectations, the predictions of the model for B physics are very close to the standard model ones. The main differences appear in processes involving the up quarks such as $D^0-\bar{D}^0$ mixing and in the electric dipole moment of the neutron, which should be close to the experimental limit. Possible deviations from the standard model predictions for CP asymmetries in B decays are also considered.

hep-ph↗
arXiv1999

Neutrino Mixing and the Pattern of Supersymmetry Breaking

We study the implications of a large $ν_μ- ν_τ$ mixing angle on lepton flavour violating radiative transitions in supersymmetric extensions of the standard model. The transition rates are calculated to leading order in $ε$, the parameter which characterizes the flavour mixing. The uncertainty of the predicted rates is discussed in detail. For models with modular invariance the branching ratio $BR(μ\to e γ)$ mostly exceeds the experimental upper limit. In models with radiatively induced flavour mixing the predicted range includes the upper limit, if the Yukawa couplings in the lepton sector are large, as favoured by Yukawa coupling unification.

hep-ph↗
arXiv1999

Leptogenesis And Inflation

In this talk, we studied the implication of the constraint on the reheating temperature coming from the gravitino problem on models of leptogenesis. We point out that in supersymmetric extensions of the standard model, all existing models of neutrino masses and leptogenesis, except the one with right-handed singlet neutrinos are ruled out for a large range of the gravitino mass.

hep-ph↗
arXiv1998

Electroweak Baryogenesis in the Presence of an Isosinglet Quark

We consider the possibility of electroweak baryogenesis in a simple extension of the standard model with an extra singlet complex scalar and a vector-like down quark. We show that in the present model the first-order electroweak phase transition can be strong enough to avoid the baryon asymmetry washout by sphalerons and that the CP-violating effects can be sufficient to explain the observed baryon-to-entropy ratio nB/s ~ 10^(-10). Other appealing features of the model include the generation of a CKM phase from spontaneous CP breaking at a high energy scale and a possible solution of the strong CP problem through the natural suppression of the parameter theta.

hep-ph↗
arXiv1998

Final State Interaction Phases in $ B \to K π$ Decay Amplitudes

A simple Regge pole model for $Kπ$ scattering explains the large $e^{i δ}$ between isospin amplitudes which is observed at the D meson mass ($δ\approx π/2$). It predicts $δ\approx 14^{\circ}- 20^{\circ}$ at the B mass. Implications for ($B \to K π$) decays and extensions of the model to other two-body decay channels are briefly discussed.

hep-ph↗
arXiv1997

Equivalence of the sine-Gordon and massive Thirring models at finite temperature

Using the path-integral approach, the quantum massive Thirring and sine-Gordon models are proven to be equivalent at finite temperature. This result is an extension of Coleman's proof of the equivalence between both theories at zero temperature. The usual identifications among the parameters of these models also remain valid at $T \neq 0$.

hep-th↗
arXiv1997

A Dynamical Scheme for a Large CP-Violating Phase

A dynamical scheme where the third generation of quarks plays a distinctive role is implemented. New interactions with a $θ$ term induce the breaking of the electroweak symmetry and the top-bottom mass splitting. A large CP-violating phase naturally follows from the latter.

hep-ph↗
arXiv1996

Electroweak baryogenesis and the Minimal Supersymmetric Standard Model

In principle, the baryon asymmetry of the Universe can be generated at the electroweak phase transition but the experimental lower limit on the Higgs mass seems to rule out a Standard Model scenario. However, it has been shown recently that in the Minimal Supersymmetric Standard Model, the electroweak phase transition can be a strong enough first order one for baryogenesis if the mass of one top squark is close to or smaller than the top mass.

hep-ph↗