118598318
One diagonal texture or cofactor zero of the neutrino mass matrix
In view of the recent measurement of nonzero $\theta_{13}$, we carry out a systematic study of a simple class of neutrino models that has one diagonal texture or cofactor zero in the mass matrix. There are seven free parameters in the model and five of them are already measured by neutrino oscillation experiments; some cases for the normal or inverted hierarchy are excluded and for the rest we obtain the preferred values for the lightest neutrino mass and Dirac CP phase. We find that there are strong similarities between one diagonal texture zero models with one mass hierarchy and one diagonal cofactor zero models with the opposite mass hierarchy. We also make predictions for neutrinoless double beta decay for these models. For the one cofactor zero models, we present a simple realization based on a new U(1) gauge symmetry.
118692088
Seesaw mechanism with four texture zeros in the neutrino Yukawa matrix
With the recent observation of nonzero \theta_{13}, five neutrino oscillation parameters are now known. By imposing four zeros in the Yukawa coupling matrix of the type I seesaw model, the number of parameters in the neutrino mass matrix is reduced to seven, and we are able to make predictions for the lightest neutrino mass, Dirac CP phase, and neutrinoless double beta decay. Four texture zeros in the Yukawa coupling matrix is equivalent to either a single texture zero or a single cofactor zero for an off-diagonal element of the light neutrino mass matrix. We find strong similarities between single texture zero models with one mass ordering and single cofactor zero models with the opposite mass ordering. In the context of a specific class of single-flavor leptogenesis models, we find additional constraints on the parameter space.
119285694
Conserved charge fluctuations and susceptibilities in strongly interacting matter
A bstractWe study the conserved charge fluctuations, as quantified by the corresponding susceptibilities, in strongly interacting matter as motived by the quark-gluon plasma. Using the gauge-gravity correspondence approach, we study the patterns of conserved charge fluctuations in two types of holographic models for QCD, the D4/D8 and the D3/D7 models. We compute and compare the quark number susceptibilities in both models and find an interesting common feature of the two: at very strong coupling higher order susceptibilities are suppressed and the conserved charge fluctuations become purely Guassian. In light of the state-of-the-art lattice QCD results we also discuss what we can learn from these susceptibilities about the underlying degrees of freedom in the 1 ~ 2Tc quark-gluon plasma and examine the viability of different ideas such as holography, quasi-particles, as well as bound states. From analyzes of second order susceptibilities we conclude that the bound states exist and are important in the 1 ~ 2Tc region. We further construct and make predictions for several ratios of fourth-order susceptibilities that can sensitively reveal such bound states.
11013537
Effect of light fermions on the confinement transition in QCD-like theories.
The dependence of the confinement transition parameters on the fermion content provides information on the mechanism of confinement. Recent progress in lattice gauge theories has allowed us to study it for a light flavor number N(f)~O(10) and found this transition to shift toward significantly stronger coupling. We propose an explanation for that: light fermions can occupy the chromomagnetic monopoles, via zero modes, making them "distinguishable" and unsuitable for Bose-Einstein condensation. Such dilution of unoccupied monopoles is compensated by stronger coupling that makes them lighter and more numerous. We also suggest that flavor-carrying quark-monopole objects account for the density beyond the quark Fermi sphere seen in the cold dense phase of N(c)=2 lattice QCD.
56455253
Facets of the QCD Phase-Diagram
In this contribution we will discuss two aspects of the matter created in ultra-relativistic heavy ion collisions. First we will attempt to define a universal measure for the fluidity of a substance, which will allow a correct comparison between the fluidity of a Quark Gluon Plasma and any well known substance. Second we will discuss current measurements of particle correlations and their implication for possible local parity violation.
118419318
Azimuthally fluctuating magnetic field and its impacts on observables in heavy-ion collisions
Article history: The heavy-ion collisions can produce extremely strong transient magnetic and electric fields. We study the azimuthal fluctuation of these fields and their correlations with the also fluctuating matter geometry (characterized by the participant plane harmonics) using event-by-event simulations. A sizable suppression of the angular correlations between the magnetic field and the 2nd and 4th harmonic participant planes is found in very central and very peripheral collisions, while the magnitudes of these correlations peak around impact parameter b ∼ 8-10 fm for RHIC collisions. This can lead to notable impacts on a number of observables related to various magnetic field induced effects, and our finding suggests that the optimal event class for measuring them should be that corresponding to b ∼ 8-10 fm. © 2012 Elsevier B.V. All rights reserved.
18402666
Quark Probability Distribution at Finite Temperature and Density
Quark deconfinement phase transition at finite temperature and density is investigated in the frame of quantum mechanics. By solv- ing the Schrodinger equation for a heavy quark in a thermal mean field, we calculate the quark probability distribution as a function of temperature and density. The confined wave function in the vacuum expands outward rapidly when the temperature and density are high enough. The obtained phase transition line agrees qualitatively with the result of lattice QCD. It is widely accepted that the collective effect of a multiparton system can change the vacuum structure of Quantum Chromodynamics (QCD)(1), and the partons confined in a hadron bag can move out when the temperature and density are high enough and form a new state of matter, the so called quark-gluon plasma (QGP)(2). This kind of new matter may be produced in the early stage of a high-energy heavy-ion collision(3). The dense partons, produced in the vacuum at high temperature or compressed at high baryon density, make the quark wave functions overlap in a space with dimension of the colliding nuclei. An important question in relativistic heavy ion collisions is how to identify the new state of matter if it is created in the early stage. According to the numerical calculation of lattice QCD(4), the critical tem- perature of quark deconfinement is about 150 MeV when the density effect is excluded. The idea that the overlap of wave functions, or the space extension of wave functions at finite temperature and density is the original reason of quark deconfinement phase transition arises naturally an interesting ques-