Fermilab top mass and modified Fritzsch mass matrices

Fritzsch like mass matrices with non-zero 22-elements both in U sector and D sector have been investigated in the context of latest data regardingm _t ^phys , |V _ub|, |V _cb|, |V _td| and |V _ts|. Unlike several other phenomenological models, the present model not only accommodates the value ofm _t ^phys in the range 150–240 GeV, encompassing the CDF and D0 values, but is also able to reproduce |V _cb| ≊0.040 and |V _ub/V_cb| = 0.08±0.02 and |V _td| is predicted to lie in the range 0.005–0.014. Further, the angles of the unitarity triangle, related to the CP-violating asymmetries, are calculated to be in the ranges −1.0⩽sin2α⩽−0.1, 0.6 ⩽sin2α⩽1.0 and 0.48⩽sin2β⩽0.56, which are in agreement with other recent calculations.     

Unitarity boomerangs of quark and lepton mixing matrices

The most popular way to present mixing matrices of quarks (CKM) and leptons (PMNS) is the parametrization with three mixing angles and one CP-violating phase. There are two major options in this kind of parametrizations, one is the original Kobayashi–Maskawa (KM) matrix, and the other is the Chau–Keung (CK) matrix. In a new proposal by Frampton and He, a unitarity boomerang is introduced to combine two unitarity triangles, and this new presentation displays all four independent parameters of the KM parametrization in the quark sector simultaneously. In this Letter, we study the relations between KM and CK parametrizations, and also consider the quark–lepton complementarity (QLC) in the KM parametrization. The unitarity boomerang is discussed in the situation of the CK parametrization for comparison with that in the KM parametrization in the quark sector. Then we extend the idea of unitarity boomerang to the lepton sector, and check the corresponding unitarity boomerangs in the two cases of parametrizations.     

Fermi matrix element with isospin breaking

Prompted by the level of accuracy now being achieved in tests of the unitarity of the CKM matrix, we consider the possible modification of the Fermi matrix element for the β  -decay of a neutron, including possible in-medium and isospin violating corrections. While the nuclear modifications lead to very small corrections once the Behrends–Sirlin–Ademollo–Gatto theorem is respected, the effect of the u−d$u-d$ mass difference on the conclusion concerning V_ud$V_{ud}$ is no longer insignificant. Indeed, we suggest that the correction to the value of |V_ud|²+|V_us|²+|V_ub|²${|V_{ud}|}^2+{|V_{us}|}^2+{|V_{ub}|}^2$ is at the level of ¹⁰⁻⁴${10}^{-4}$.     

Precision flavour physics and supersymmetry

We review the salient features of a comparative study of the profile of the CKM unitarity triangle, and the resulting CP-violating phases , β and γ in B decays, in the standard model and in several variants of the minimal supersymmetric standard model (MSSM), reported recently by us. These theories are characterized by a single phase in the quark flavour mixing matrix and give rise to well-defined contributions in the flavour-changing-neutral-current transitions in K and B decays. We analyse the supersymmetric contributions to the mass differences in the B_d⁰– and B_s⁰– systems, ΔM_d and ΔM_s, respectively, and to the CP-violating quantity || in K decays. Our analysis shows that the predicted ranges of β in the standard model and in MSSM models are very similar. However, precise measurements at B-factories and hadron machines may be able to distinguish these theories in terms of the other two CP-violating phases and γ.     

A timeon model of quark and lepton mass matrices

It is proposed that T violation in physics, as well as the masses of electron and quarks, arise from a pseudoscalar interaction with a new spin 0 field τ(x), odd in P and T, but even in C. This interaction contains a factor iγ₅ in the quark and lepton Dirac algebra, so that the full Hamiltonian is conserving; but by spontaneous symmetry breaking, the new field τ(x) has a nonzero expectation value τ≠0 that breaks P and T symmetry. Oscillations of τ(x) about its expectation value produce a new particle, the “timeon”. The mass of timeon is expected to be high because of its flavor-changing properties.The main body of the paper is on the low energy phenomenology of the timeon model. As we shall show, for the quark system the model gives a compact three-dimensional geometric picture consisting of two elliptic plates and one needle, which embodies the 10 observables: six quark masses, three Eulerian angles and the Jarlskog invariant of the CKM matrix.For leptons, we assume that the neutrinos do not have a direct timeon interaction; therefore, the lowest neutrino mass is zero. The timeon interaction with charged leptons yields the observed nonzero electron mass, analogous to the up and down quark masses. Furthermore, the timeon model for leptons contains two fewer theoretical parameters than observables. Thus, there are two testable relations between the three angles and the Jarlskog invariant of the neutrino mapping matrix.     

Yukawaon model in the quark sector and nearly tribimaximal neutrino mixing

For the purpose of deriving the observed nearly tribimaximal neutrino mixing, a possible yukawaon model in the quark sector is investigated. Five observable quantities (2 up-quark mass ratios and 3 neutrino mixing parameters sin²2θ_atm, tan²θ_solar and |U₁₃|) are excellently fitted by two parameters (one in the up-quark sector and another one in the right-handed Majorana neutrino sector).     

Neutron β-decay, Standard Model and cosmology

The precise value of the neutron lifetime is of fundamental importance to particle physics and cosmology. The neutron lifetime recently obtained, 878.5±0.7_stat±0.3_sys s, is the most accurate one to date. The new result for the neutron lifetime differs from the world average value by 6.5σ. The impact of the new result on testing of Standard Model and on data analysis for the primordial nucleosynthesis model is scrutinized.     

Non-Hermitian perturbations to the Fritzsch textures of lepton and quark mass matrices

We show that non-Hermitian and nearest-neighbor-interacting perturbations to the Fritzsch textures of lepton and quark mass matrices can make both of them fit current experimental data very well. In particular, we obtain θ₂₃?45°${\theta }_{23}?45\text{°}$ for the atmospheric neutrino mixing angle and predict θ₁₃?3°${\theta }_{13}?3\text{°}$ to 6° for the smallest neutrino mixing angle when the perturbations in the lepton sector are at the 20% level. The same level of perturbations is required in the quark sector, where the Jarlskog invariant of CP violation is about 3.7×¹⁰⁻⁵$3.7\times {10}^{-5}$. In comparison, the strength of leptonic CP violation is possible to reach about 1.5×¹⁰⁻²$1.5\times {10}^{-2}$ in neutrino oscillations.     

Testing CVC and CKM Unitarity via Superallowed Nuclear Beta Decay

Superallowed nuclear beta decay between 0+ analog states is a sensitive probe of the weak interaction, with the established strength – or Ft value – of each such transition being a direct measure of the vector coupling constant, GV. Each transition’s Ft value depends on the half-life of the parent nucleus as well as on the Q-value and branching ratio for the transition of interest. It also depends on small (1%) transition-dependent theoretical corrections, of which the most sensitive accounts for isospin symmetry breaking. We have recently published a new survey of world superallowed-decay data, which establishes the Ft values of 14 separate superallowed transitions to a precision of order 0.1% or better. The results from this very robust data set yield the value of Vud, the up-down quark mixing element of the Cabibbo-Kobayashi-Maskawa (CKM) matrix, and lead to the most demanding test available of CKM unitarity. The survey results and their outcome are described, as is the current direction of experiments that focus on testing the validity of the isospin-symmetry-breaking corrections.     

General scan in flavor parameter space in models with vector quark doublets and an enhancement in the B→X_sγ process

In models with vector-like quark doublets, the mass matrices of up and down type quarks are related.Precise diagonalization of the mass matrices has become an obstacle in numerical studies. In this work we first propose a diagonalization method. As its application, in the Standard Model with one vector-like quark doublet we present the quark mass spectrum and Feynman rules for the calculation of B → X_sγ. We find that i) under the constraints of the CKM matrix measurements, the mass parameters in the bilinear term are constrained to a small value by the small deviation from unitarity; ii) compared with the fourth generation extension of the Standard Model, there is an enhancement to the B → X_sγ process in the contribution of vector-like quarks, resulting in a non-decoupling effect in such models.     

Non-perturbative corrections to one-gluon exchange quark potentials

The leading non-perturbative QCD corrections to the one-gluon exchange quark-quark, quark-antiquark and pair-excitation potentials are derived by using a covariant form of non-local two-quark and two-gluon vacuum expectation values. Our numerical calculation indicates that the correction of quark and gluon condensates to the quark-antiquark potential improves the heavy quarkonium spectra to some degree.     

Dynamic color screening in a classical quark plasma

Screening of a moving infinite color sheet source is examined in a quark plasma at finite temperature. The classical chromohydrodynamic equations for quarks are integrated, to obtain profiles for quark current density, which in turn are used to solve the SU(2) Yang-Mills equations numerically. This provides a classical but non-perturbative treatment for the screening of a moving source in quark plasma. The results show two interesting features. We observe that if the test source is at rest the screening does not depend on the color dynamics and the behavior is very similar to that in Coulomb plasma. When the test source is moving with non-relativistic velocity the non-abelian features manifest themselves by weakening the screening and also by exhibiting an oscillatory profile with distance.     

Color superconductivity in dense quark matter

The possible structure of the QCD phase diagram is discussed focusing on color superconducting quark matter in the region of low temperatures and moderately large densities, which could be relevant for compact stars.     

Surface structure of quark stars with magnetic fields

We investigate the impact of magnetic fields on the electron distribution of the electrosphere of quark stars. For moderately strong magnetic fields of B ∼ 10¹³ G, quantization effects are generally weak due to the large number density of electrons at surface, but can nevertheless affect the photon emission properties of quark stars. We outline the main observational characteristics of quark stars as determined by their surface emission, and briefly discuss their formation in explosive events termed as quark-novae, which may be connected to the r-process.     

Perturbative and nonperturbative quark masses in structure functions

Flavour symmetry breaking is introduced in the approximate formula for quark mass reported earlier. We use SLAC-MIT as well as NMC data to estimate the up, down and strange quark masses from structure functions. Using the approximateQ ² evolutions of Altarelli-Parisi equations, we also estimate its perturbative and nonperturbative components.     

Collective thermalization in quark gluon plasma

A very important question in ultrarelativistic heavy ion collisions is that of thermalization of the high energy density quark gluon plasma forud in the central rapidity region. Different approaches have been adopted by various authors to study this thermalization problem. These include phenomenological string and capacitor plate models, perturbative QCD based parton cascade models and the classical non-perturbative approach. In this paper we briefly review the earlier studies and discuss our work which emphasizes the role of non-perturbative collective effects (classical chaos) in the thermalization of the plasma. In particular, using classical equations of motion of a coloured parton in self-consistent colour fields, we have carried out a 1+1 dimensional simulation of coloured partonic matter. We find that in certain parameter domains, the system exhibits chaotic behaviour in non-abelian plasma oscillations, which then leads to thermalization of the plasma.     

Standard-Model Tests with Superallowed β-Decay: An Important Application of Very Precise Mass Measurements

Superallowed β-decay provides a sensitive means for probing the limitations of the Electroweak Standard Model. To date, the strengths (ft-values) of superallowed 0⁺→0⁺ β-decay transitions have been determined with high precision from nine different short-lived nuclei, ranging from ¹⁰C to ⁵⁴Co. Each result leads to an independent measure for the vector coupling constant G _V and collectively the nine values can be used to test the conservation of the weak vector current (CVC). Within current uncertainties, the results support CVC to better than a few parts in 10,000 - a clear success for the Standard Model! However, when the average value of G _V, as determined in this way, is combined with data from decays of the muon and kaon to test another prediction of the Standard Model, the result is much more provocative. A test of the unitarity of the Cabibbo-Kobayashi-Maskawa matrix fails by more than two standard deviations. This result can be made more definitive by experiments that require extremely precise mass measurements, in some cases on very short-lived (≤100 ms) nuclei. This talk presents the current status and future prospects for these Standard-Model tests, emphasizing the role of precise mass, or mass-difference measurements. There remains a real challenge to mass-measurement technique with the opportunity for significant new results. This revised version was published online in July 2006 with corrections to the Cover Date.     

Studying pion effects in the quark propagator

Within the framework of Schwinger-Dyson and Bethe-Salpeter equations we investigate the importance of pions for the quark-gluon interaction. To this end we choose a truncation for the quark-gluon vertex that includes intermediate pion degrees of freedom and adjust the interaction such that unquenched lattice results for various current quark masses are reproduced. After extrapolation to the physical point we find a considerable contribution of the pion back reaction to the quark mass function as well as to the chiral condensate.     

Photon production from quark gluon plasma at finite baryon density

The photon yield from a baryon-rich quark gluon plasma (QGP) at SPS energy has been estimated. In the QGP phase, rate of photon production is evaluated up to two-loop level. In the hadron phase, dominant contribution from π,ρ, ω mesons has been considered. The evolution of the plasma has been studied with appropriate equation of state in both QGP and hadron phase for a baryon-rich system. At SPS energy, the total photon yield is found to increase marginally in the presence of baryon density.