arXiv subjects

P. Castorina

Publications and source records attributed to P. Castorina.

At least 55 records · Page 3Linked to original sources

arXiv2008

An alternative heavy Higgs mass limit

After commenting on the present value of the Higgs particle mass from radiative corrections, we explore the phenomenological implications of an alternative, non-perturbative renormalization of the scalar sector where the mass of the Higgs particle does not represent a measure of observable interactions at the Higgs mass scale. In this approach the Higgs particle could be very heavy, even heavier than 1 TeV, and remain nevertheless a relatively narrow resonance.

hep-ph↗

arXiv2008

The Thermal Production of Strange and Non-Strange Hadrons in e+e- Collisions

The thermal multihadron production observed in different high energy collisions poses two basic problems: (1) why do even elementary collisions with comparatively few secondaries (e+e- annihilation) show thermal behaviour, and 2) why is there in such interactions a suppression of strange particle production? We show that the recently proposed mechanism of thermal hadron production through Hawking-Unruh radiation can naturally account for both. The event horizon of colour confinement leads to thermal behaviour, but the resulting temperature depends on the strange quark content of the produced hadrons, causing a deviation from full equilibrium and hence a suppression of strange particle production. We apply the resulting formalism to multihadron production in e+e- annihilation over a wide energy range and make a comprehensive analysis of the data in the conventional statistical hadronization model and the modified Hawking-Unruh formulation. We show that this formulation provides a very good description of the measured hadronic abundances, fully determined in terms of the string tension and the bare strange quark mass; it contains no adjustable parameters.

hep-ph↗

arXiv2008

The Exact String Black-Hole behind the hadronic Rindler horizon?

The recently suggested interpretation of the universal hadronic freeze-out temperature T_f ~ 170 Mev - found for all high energy scattering processes that produce hadrons: e+ e-, p p, p anti-p, pi p, etc. and N N' (heavy-ion collisions) - as a Unruh temperature triggers here the search for the gravitational black-hole that in its near-horizon approximation better simulates this hadronic phenomenon. To identify such a black-hole we begin our gravity-gauge theory phenomenologies matching by asking the question: which black-hole behind that Rindler horizon could reproduce the experimental behavior of T_f (\sqrt{s}) in N N', where \sqrt{s} is the collision energy. Provided certain natural assumptions hold, we show that the exact string black-hole turns out to be the best candidate (as it fits the available data on T_f (\sqrt{s})) and that its limiting case, the Witten black-hole, is the unique candidate to explain the constant T_f for all elementary scattering processes at large energy. We also are able to propose an effective description of the screening of the hadronic string tension sigma(mu_b) due to the baryon density effects on T_f.

hep-th↗

arXiv2007

Thermal Hadronization, Hawking-Unruh Radiation and Event Horizon in QCD

Because of colour confinement, the physical vacuum forms an event horizon for quarks and gluons; this can be crossed only by quantum tunneling, i.e., through the QCD counterpart of Hawking radiation by black holes. Since such radiation cannot transmit information to the outside, it must be thermal, of a temperature determined by the strong force at the confinement surface, and it must maintain colour neutrality. The resulting process provides a common mechanism for thermal hadron production in high energy interactions, from $e^+e^-$ annihilation to heavy ion collisions. The analogy with black-hole event horizon suggests a dependence of the hadronization temperature on the baryon density.

hep-ph↗

arXiv2007

Hybrid neutron stars within the Nambu-Jona-Lasinio model and confinement

Recently, it has been shown that the standard Nambu-Jona-Lasinio (NJL) model is not able to reproduce the correct QCD behavior of the gap equation at large density, and therefore a different cutoff procedure at large momenta has ben proposed. We found that, even with this density dependent cutoff procedure, the pure quark phase in neutron stars (NS) interiors is unstable, and we argue that this could be related to the lack of confinement in the original NJL model.

hep-ph↗

arXiv2007

Thermal Hadronization and Hawking-Unruh Radiation in QCD

We conjecture that because of color confinement, the physical vacuum forms an event horizon for quarks and gluons which can be crossed only by quantum tunneling, i.e., through the QCD counterpart of Hawking radiation by black holes. Since such radiation cannot transmit information to the outside, it must be thermal, of a temperature determined by the chromodynamic force at the confinement surface, and it must maintain color neutrality. We explore the possibility that the resulting process provides a common mechanism for thermal hadron production in high energy interactions, from $e^+e^-$ annihilation to heavy ion collisions.

hep-ph↗

arXiv2007

Quark matter in neutron stars within the Nambu - Jona-Lasinio model and confinement

The quark matter equation of state (EOS) derived from the standard Nambu - Jona-Lasinio (NJL) model is soft enough to render neutron stars (NS) unstable at the onset of the deconfined phase, and no pure quark matter can be actually present in its interior. Since this is a peculiarity of the NJL model, we have studied a modified NJL model with a momentum cut-off which depends on the density. This procedure, which improves the agreement between QCD and NJL model at large density, modifies the standard NJL equation of state, and then it is potentially relevant for the stability analysis of neutron stars. We show that also within this approach, the NS instability still persists, and that the vacuum pressure, as a signal of quark confinement, has a fundamental role for the NS stability. In this respect, our conclusions point to a relationship between confinement and NS stability.

hep-ph↗

arXiv2006

Growth Laws in Cancer: Implications for Radiotherapy

Comparing both, the more conventional Gompertz tumor growth law (GL) and the ``Universal'' law (UL), recently proposed and applied to cancer,we have investigated the growth law's implications on various radiotherapy regimen. According to GL, the surviving tumor cell fraction could be reduced 'ad libidum', independently of the initial tumor mass,simply by increasing the number of treatments. On the contrary, if tumor growth dynamics would indeed follow the Universal scaling law, there is a lower limit of the survival fraction that cannot be reduced any further regardless of the total number of treatments. This finding can explain the so called ``tumor size effect'' and re-emphasizes the importance of early diagnosis as it implies that radiotherapy may be successful provided the tumor mass at treatment onset is rather small. Taken together with our previous works, implications of these findings include revisiting standard radiotherapy regimen and overall treatment protocols.

physics.med-ph↗

arXiv2006

Scaling of variables and the relation between noncommutative parameters in Noncommutative Quantum Mechanics

We consider Noncommutative Quantum Mechanics with phase space noncommutativity. In particular, we show that a scaling of variables leaves the noncommutative algebra invariant, so that only the self-consistent effective parameters of the model are physically relevant. We also discuss the recently proposed relation of direct proportionality between the noncommutative parameters, showing that it has a limited applicability.

hep-th↗

arXiv2006

A Classification Scheme for Phenomenological Universalities in Growth Problems

A classification in universality classes of broad categories of phenomenologies, belonging to different disciplines, may be very useful for a crossfertilization among them and for the purpose of pattern recognition. We present here a simple scheme for the classification of nonlinear growth problems. The success of the scheme in predicting and characterizing the well known Gompertz, West and logistic models suggests to us the study of a hitherto unexplored class of nonlinear growth problems.

physics.bio-ph↗

arXiv2005

Effective degrees of freedom of the Quark-Gluon Plasma

The effective degrees of freedom of the Quark-Gluon Plasma are studied in the temperature range $\sim 1-2$ $ T_c$. Employing lattice results for the pressure and the energy density, we constrain the quasiparticle chiral invariant mass to be of order 200 MeV and the effective number of bosonic resonant states to be at most of order $\sim 10$. The chiral mass and the effective number of bosonic degrees of freedom decrease with increasing temperature and at $T \sim 2$ $T_c$ only quark and gluon quasiparticles survive. Some remarks regarding the role of the gluon condensation and the baryon number-strangeness correlation are also presented.

hep-ph↗

arXiv2005

Nambu Jona-Lasinio Model of \bar q q Bose Einstein Condensation and pseudogap phase

We show the existence of a pseudogap phase in the Nambu Jona-Lasinio model of quark interactions. In the pseudogap phase chiral symmetry is restored but q\bar q pseudoscalar mesons still exist and they are massive. Such a behavior is intermediate between a BCS superconductor and a Bose Einstein Condensate. We suggest the relevance of this phenomenon for an understanding of recent lattice QCD and experimental data.

hep-ph↗

arXiv2005

Noncommutative Gravitational Quantum Well

We study noncommutative geometry at the Quantum Mechanics level by means of a model where noncommutativity of both configuration and momentum spaces is considered. We analyze how this model affects the problem of the two-dimensional gravitational quantum well and use the latest experimental results for the two lowest energy states of neutrons in the Earth's gravitational field to establish an upper bound on the fundamental momentum scale introduced by noncommutativity, namely $\sqrtη\lesssim1\ \mathrm{meV/c}$, a value that can be improved in the future by up to 3 orders of magnitude. We show that the configuration space noncommutativity has, in leading order, no effect on the problem. We also analyze some features introduced by the model, specially a correction to the presently accepted value of Planck's constant to 1 part in $10^{24}$.

hep-th↗

arXiv2004

Nucleon correlations and Higher Twist effects in nuclear structure functions

The overlap of the nucleons in nuclei plays an important role in understanding the nuclear dependence of deep inelastic scattering data. It is shown that the nuclear modification of the higher twist scale can be essentially determined by the overlapping volume per nucleon and this effect gives a large contribution to nuclear shadowing for small $x$ and low $Q^2$. In this kinematical region there is also a moderate enhancement of the longitudinal structure function in nuclei.

nucl-th↗

arXiv2004

Gluon condensation and deconfinement critical density in nuclear matter

An upper limit to the critical density for the transition to the deconfined phase, at zero temperature, has been evaluated by analyzing the behavior of the gluon condensate in nuclear matter. Due to the non linear baryon density effects, the upper limit to the critical density, ρ_c turns out about nine times the saturation density, rho_0 for the value of the gluon condensate in vacuum <(α_s/π) G^2>=0.012 GeV^4. For neutron matter ρ_c \simeq 8.5 ρ_0. The dependence of the critical density on the value of the gluon condensate in vacuum is studied.

nucl-th↗

arXiv2004

Violation of Lorentz invariance and dynamical effects in high energy gamma rays

The relation between the violation of Lorentz invariance and the dynamical effects in high energy gamma rays production is discussed. By using the framework of noncommutative classical electrodynamics, it is shown that full dynamical calculations are required to put bounds on the Lorentz violating scale by the phenomenological analysis of these processes as, for example, the synchrotron radiation from the CRAB nebula. It is observed that an improvement of the present bound on the scale of noncommutativity can be obtained only by astrophysical observations of gamma ray spectra in strong magnetic fields such as pulsars.

hep-ph↗

arXiv2003

Renormalization group analysis of the three-dimensional Gross-Neveu model at finite temperature and density

The Renormalization Group flow equations obtained by means of a proper time regulator are used to analyze the restoration of the discrete chiral symmetry at non-zero density and temperature in the Gross-Neveu model in d=2+1 dimensions. The effects of the wave function renormalization of the auxiliary scalar field on the transition have been studied. The analysis is performed for a number of fermion flavors N_f=12 and the limit of large N_f is also considered. The results are compared with those coming from lattice simulations.

hep-th↗

arXiv2003

Noncommutative Synchrotron

We study the departures from the classical synchrotron radiation due to noncommutativity of coordinates. We find that these departures are significant, but do not give tight bounds on the magnitude of the noncommutative parameter. On the other hand, these results could be used in future investigations in this direction. We also find an acausal behavior for the electromagnetic field due to the presence in the theory of two different speeds of light. This effect naturally arises even if only θ^{12} is different from zero.

hep-th↗