0000000000099695
AUTHOR
José Bernabeu Alberola
Intrinsic magnetic polarizability contribution to susceptibility of dense neutron matter
It is shown that, apart from the neutron interaction contribution to the susceptibility of neutron stars, there is an additional contribution coming from the magnetic polarizability beta /sub n/ of individual neutrons. For beta /sub n/ approximately=10/sup -4/fm/sup 3 /, this part overwhelms the interaction contribution for k/sub F/>or approximately=3.5fm/sup -1/. No transition to ferromagnetic state is predicted in the interesting density region.
Eta Gamma Z anomaly from the eta ->gamma mu(+)mu(-) decay
We show that the eta gamma Z anomaly can be measured by analysing parity-violating effects in the eta --> gamma mu(+)mu(-) decay. In this sense, we find that the longitudinal polarization of the outgoing mu(+) is an appropriate observable to be considered in future high-statistics eta factories. The effect is expected to lie in the range 10(-5)-10(-6) in the Standard Model.
Delta t-dependent equal-sign dilepton asymmetry and CPTV effects the symmetry of the B-0-(B)over-bar(0) entangled state
In this paper we discuss experimental consequences of a novel kind of CPT violation which would manifest itself in the symmetry of the entangled initial state of B-0 and (B) over bar (0) through their loss of indistinguishability. The 'wrong' symmetry component is proportional to omega. We focus our theoretical study on the Delta t-dependence of observables concerning equal-sign dilepton events for which the intensity vanishes at Delta t = 0 in absence of omega. We find that the charge asymmetry, A(sl), acquires a Delta t-dependence linear in !, whose relative importance appears on specific regions of time still unexplored. We also do a statistical analysis for the measurements here propose…
On the observability of the neutrino charge radius
It is shown that the probe-independent charge radius of the neutrino is a physical observable; as such, it may be extracted from experiment, at least in principle. This is accomplished by expressing a set of experimental neutrino-electron cross-sections in terms of the finite charge radius and two additional gauge- and renormalization-group-invariant quantities, corresponding to the electroweak effective charge and mixing angle.
On the history of the PMNS Matrix... with today's perspective
The conceptual basis for understanding the interplay of neutrino mass and mixing for neutrino oscillations were paradoxically discussed in a period when the prevailing view was that of massless neutrinos. The name of Bruno Pontecorvo is associated to most of the components for this beautiful quantum phenomenon: muon-electron universality, different neutrino flavours, mismatch between weak interaction and mass eigenstates, neutrino oscillation phenomenology, including flavour and Majorana transitions.
Tau-odd correlation on the Z0-Peak
T-odd observables can be due either to T-violation or to unitarity corrections. We find a non-vanishing expectation value of a T-odd operator for from one-loop electroweak corrections to the resonant decay and from interference with the background. For unpolarized beams, chirality conservation allows only one relevant absorptive part of the interference between different amplitudes. We identify this unique T-odd effect as the spin correlation , where are the transverse (within the production plane) and normal (to the plane) spin components for f and , respectively. In the standard theory it is generated from the Z, W exchanges in the final vertex, from the Z-γ self-energy and from the tree-…
Dificultades en la enseñanza/aprendizaje de la física cuántica
Abstract We have elaborated a questionnaire about some selected basic concepts on Modern Physics, We have then analysed the students comprehension level on Quantum Physics before they follow this matter in the 3er year of Physics studies. Once this course has been completed. the evolution of the previous misconceptions is studied. We conclude that a teaching which considers previous misconceptions results in a sensitive improvement. However, we also detect the persistence of a few misconceptions acquired during the non-university teaching.
Dynamical zero in (v)over-bar(e)-e(-) scattering and the neutrino magnetic moment
The Standard Model differential cross section for ν¯e−e− elastic scattering vanishes exactly, at lowest order, for forward electrons and incident ν¯e energy close to the rest energy of the electron. This dynamical zero is not induced by a fundamental symmetry of the Lagrangian but by a destructive interference between the left- and right-handed chiral couplings of the electron in the charged and neutral current amplitudes. We show that lowest order analyses based on this favorable kinematic configuration are only mildly affected by the inclusion of the O(α) radiative corrections in the ν¯e−e− differential cross section, thus providing an excellent opportunity for the search of ``new physics…
Low-energy elastic neutrino-nucleon and nuclear scattering and its relevance for supernovae
Low-energy (E/sub v/10, spin- (if any) and isospin-dependent effects are comfortably below 10% of the coherent scattering. In the case of the neutron, the cross-section for momentum transfer, when compared to that of the isoscalar current, is: i) more than one order of magnitude larger in model I; ii) about twice larger in model II. It is noted that the vector model gives more dramatic effects in the supernova 'strategy' both lowering the cross-section in the inner core and increasing it in the outer region. (16 refs).
Constraints on the W-R mass and CP violation in left-right models
We update the constraints on the right-handed WR gauge boson mass, mixing angle ζ with the left-handed WL gauge boson, and other parameters in general left-right symmetric models with different mechanisms of CP violation. Constraints mostly independent of any assumption on the quark sector are obtained from a re-analysis of muon decay data. Estimates of the left-right hadronic matrix elements in the neutral kaon system and their uncertainties are revised using large Nc and Chiral Perturbation Theory arguments. With explicitly given assumptions on the long-distance (ΔS=1)2 contributions to the KL−KS mass difference, lower bounds on MWR are obtained. With the same assumptions, one also gets s…
Analytic O(alpha_s) Results for Bottom and Top Quark Production in e+ e- Collisions
We present a new derivation of the O(alpha_s) angular distribution of the outgoing $q$-quark in the production process $e^+ e^- \to\gamma,Z\to q\,\bar{q}(g)$. In our calculation, we express the three-particle phase-space integration of the gluon-bremsstrahlung process in terms of a general set of analytic integral solutions. A consistent treatment of the QCD one-loop corrections to the axial-vector current deserves special attention. This is relevant in the derivation of the forward-backward asymmetry predicted by the standard model. Finally, we provide the full analytical solutions for the differential rates in closed form and conclude with numerical estimates for bottom and top quark prod…
The Electromagnetic Polarizabilities of the Proton and the Scalar-Isoscalar gamma gamma --> pi pi Amplitude
In a dispersive approach to the calculation of the electromagnetic polarizabilities of the proton, the sensitivity to the annihilation channel input is analyzed. It is shown that the isoscalar s wave absorptive part gives the overwhelming contribution. The connection with the poorly known γγ→ππ amplitude is established and some numerical estimates are presented.
Neutrino magnetic moment and the process neutrino e ---> neutrino e gamma
The contribution of a neutrino magnetic moment mu(nu) to the cross section of the process ve(-) --> ve(-)gamma has been calculated and compared with the Standard Electroweak one. The radiative process allows to reach low enough values of Q(2) without the need to operate at very small energies of recoil electrons. Regions in the phase space which are more favourable to set bounds on mu(v) are suggested.
Time reversal violation from the entangled B-0(B)over-bar(0) system
We discuss the concepts and methodology to implement an experiment probing directly Time Reversal (T) non-invariance, without any experimental connection to CP violation, by the exchange of 'in' and 'out' states. The idea relies on the B0-antiB0 entanglement and decay time information available at B factories. The flavor or CP tag of the state of the still living neutral meson by the first decay of its orthogonal partner overcomes the problem of irreversibility for unstable systems, which prevents direct tests of T with incoherent particle states. T violation in the time evolution between the two decays means experimentally a difference between the intensities for the time-ordered (l^+ X, J…
Top quark mass from radiative corrections to the Z ---> b anti-b decay
The one-loop correction to the ZbbBAR vertex presents a quadratic dependence on the top-quark mass, which has its origin in the spontaneous symmetry breaking mechanism of the Standard Model. We study the possibility of fixing the top mass by comparing LEP measurements with theoretical predictions. Using the MSBAR renormalization scheme, we calculate the top mass dependence of the ZbbBAR vertex. For all Z-widths, we give simple approximate formulae which work at the 0.05% level. It is found that if some branching ratios involving the b-quark are measured at the 0.5% level the top mass will be determined with an error of 30 GeV using only LEP1 experiments.
Polarizability contribution to energy-levels of muonic helium (mu4he)
An experiment measuring the 2S-2P separation in the ion ( mu /sup 4 /He)/sup +/ is in progress at CERN. Comparison of the outcome of this experiment with the prediction of quantum electrodynamics requires the knowledge of the hadronic correction due to the two-photon exchange mechanism. Therefore, the authors have calculated the correction to the energy levels of the ion ( mu /sup 4/He)/sup +/ due to this mechanism. The hadronic contribution to the 2S-2P separation is found to be approximately 16 AA which is about three times larger than the expected experimental uncertainty.
Origin of discrepancy in theoretical value of polarizability correction to (mu-he-4)+ energy-levels
Different approaches in calculating the polarizability correction to the energy levels of the muonic 4 He ion are compared. These calculations disagree with each other by giving results 3 to 10 times larger than the experimental uncertainty. The origin of the major discrepancy is traced to the treatment of the nuclear excitations. It is shown that the experimental value of the electric polarizability of 4 He provides a crucial restriction on model calculations.
CPT violation in entangled BO-anti-BO states and the demise of flavour tagging
We discuss the demise of flavour tagging due to the loss of the particle-antiparticle identity of neutral B-mesons in the Einstein-Podolsky-Rosen correlated states. Such a situation occurs in cases where the CPT operator is ill-defined, as happens, for example, in quantum gravity models with induced decoherence in the matter sector. The time evolution of the perturbed B0-B0bar initial state, as produced in B-factories, is sufficient to generate new two-body states. For flavour specific decays at equal times, we discuss two definite tests of the two body entanglement: (i) search for the would-be forbidden B0 B0 and B0bar B0bar states; (ii) deviations from the indistinguishable probability be…
Axial current in extended systems
We establish a connection between the nuclear axial current and pionic properties in the medium. As a strict consequence of PCAC alone, the time component has its matrix elements determined by a wave pion absorption to leading order in the momentum transfer. The properties of the system are governed by scale parameters associated both with its size and with the local interaction structure. Based on this observation we suggest a locality condition for the part of the axial current which has no pion pole. It follows that the full axial current can be explicitly constructed from the local s and p wave pion source functions. A model illustration is presented. Our approach unifies in a model ind…
CP nonconservation at he Z0 Peak
The measurement of a nonvanishing asymmetry α≡[Γ(sb¯)−Γ(s¯b)][Γ(sb¯)+Γ(s¯b)] would signal CP nonconservation in Z0 decays. We study here this effect within the standard model. In the three-generation case, the α value comes out small because of the effective degeneracy of u and c quarks at these high energies. In the four-generation case, results are encouraging for the CERN e+e− collider LEP: One could have a branching ratio of this flavor-changing decay to the flavor-conserving one of ∼10−6 and reach α values near unity.
The Physics of the B Factories
This work is on the Physics of the B Factories. Part A of this book contains a brief description of the SLAC and KEK B Factories as well as their detectors, BaBar and Belle, and data taking related issues. Part B discusses tools and methods used by the experiments in order to obtain results. The results themselves can be found in Part C.
Tau electric dipole moments al low energies
Low energy tau pair production, at B factories and on top of the Υ resonances, allows for a detailed investigation on the CP violation at the electromagnetic tau pair production vertex. High statistic available at low energies offers the opportunity for an independent analysis of CP-violation in the T lepton physics. We show that stringent and independent bounds on the T electric dipole moment, competitive with the high energy measurements, can be established in low energies experiments