443 research outputs found
Relativistic two-body calculation of -mesons radiative decays
This paper is a prosecution of a previous work where we presented a unified
two-fermion covariant scheme which produced very precise results for the masses
of light and heavy mesons. We extend the analysis to some radiative decays of
mesons and we
calculate their branching ratios and their widths. For most of them we can make
a comparison with experimental data finding a good agreement.For the decays for
which data are not available we compare ours with other recent theoretical
previsions.Comment: 7 pages, 1 figur
Foldy-Wouthuysen Transformation for a Spinning Particle with Anomalous Magnetic Moment
We study the Foldy-Wouthuysen transformation for a pseudoclassical particle
with anomalous magnetic moment in an external, stationary electromagnetic
field. We show that the transformation can be expressed in a closed form for
neutral particles in purely electrostatic fields and for neutral and charged
particles in external magnetostatic fields. The explicit expressions of the
diagonalized Hamiltonians are calculated.Comment: 10 page
A NJL-based study of the QCD critical line
We employ a 3 flavor NJL model to stress some general remarks about the QCD
critical line. The dependence of the critical curve on
and is discussed. The quark masses are varied to
confirm that, in agreement with universality arguments, the order of transition
depends on the number of active flavors . The slope of the critical curve
vs. chemical potential is studied as a function of . We compare our
results with those recently obtained in lattice simulations to establish a
comparison among different models.Comment: 17 pages, 5 figure
Neutral hadrons disappearing into the darkness
We study the invisible decay of neutral hadrons in a representative model of the dark sector. The mesons KL and B0
decay into the dark sector with branching rates that can be at the current experimental limits. The neutron decays with a rate that could either explain the neutron lifetime puzzle (although only for an extreme choice of the parameters and a fine-tuned value of the masses) or be just above the current limit of its invisible decay (\u3c4 inv N 73 1029 \u2009years) if kinematically allowed. These invisible decays of ordinary matter provide a novel and promising window into new physics that should be vigorously pursued
Precision diboson measurements at hadron colliders
We discuss the measurements of the anomalous triple gauge couplings at Large Hadron Collider focusing on the contribution of the O-3W and O-3 (W) over tilde operators. These deviations were known to be particularly hard to measure due to their suppressed interference with the SM amplitudes in the inclusive processes, leading to approximate flat directions in the space of these Wilson coefficients. We present the prospects for the measurements of these interactions at HL-LHC and HE-LHC using exclusive variables sensitive to the interference terms and taking carefully into account effects appearing due to NLO QCD corrections
The Classical Relativistic Quark Model in the Rest-Frame Wigner-Covariant Coulomb Gauge
The system of N scalar particles with Grassmann-valued color charges plus the
color SU(3) Yang-Mills field is reformulated on spacelike hypersurfaces. The
Dirac observables are found and the physical invariant mass of the system in
the Wigner-covariant rest-frame instant form of dynamics (covariant Coulomb
gauge) is given. From the reduced Hamilton equations we extract the second
order equations of motion both for the reduced transverse color field and the
particles. Then, we study this relativistic scalar quark model, deduced from
the classical QCD Lagrangian and with the color field present, in the N=2
(meson) case. A special form of the requirement of having only color singlets,
suited for a field-independent quark model, produces a ``pseudoclassical
asymptotic freedom" and a regularization of the quark self-energy.Comment: 81 pages, RevTe
Pseudoscalar and scalar meson masses at finite temperature
The composite operator formalism is applied to QCD at finite temperature to
calculate the masses of scalar and pseudoscalar mesons. In particular the ratio
of the sigma mass to the pion mass is an interesting measure of the degree of
chiral symmetry breaking at different temperatures. We calculate the
temperature T* at which M_sigma(T) < 2M_pi(T), above which the sigma partial
width into two pions vanishes. We find T*=0.95T_c (where T_c is the critical
temperature for the chiral phase transition), within the full effective
potential given by the formalism. We find that an expansion a-la Landau of the
effective potential around the critical point in the limit of small quark mass
provides for a very good determination of T*.Comment: 19 pages, Revtex, 2 Postscript figure
Minimal flavor violation in the see-saw portal
We consider an extension of the Standard Model with two singlet leptons, with masses in the electroweak range, that induce neutrino masses via the see-saw mechanism, plus a generic new physics sector at a higher scale, Λ. We apply the minimal flavor violation (MFV) principle to the corresponding Effective Field Theory (νSMEFT) valid at energy scales E ≪ Λ. We identify the irreducible sources of lepton flavor and lepton number violation at the renormalizable level, and apply the MFV ansätz to derive the scaling of the Wilson coefficients of the νSMEFT operators up to dimension six. We highlight the most important phenomenological consequences of this hypothesis in the rates for exotic Higgs decays, the decay length of the heavy neutrinos, and their production modes at present and future colliders. We also comment on possible astrophysical implications
Ising-like dynamical signatures and the end-point of the QCD transition line
An increase in the size of coherent domains in the one component
field theory under the influence of a uniformly changing external magnetic
field near the critical end-point was proposed
recently as an estimate also for the variation of the chiral correlation length
of QCD near its respective hypothetical end point in the
plane. The present detailed numerical investigation of the effective model
suggests that passing by the critical QCD end point with realistic rate of
temperature change will trigger large amplitude oscillations in the temporal
variation of the chiral correlation length. A simple mechanism for producing
this phenomenon is suggested.Comment: 10 pages, RevTeX, 5 figures. Version accepted for publication in PR
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