Parity Conservation Research Articles

Dilepton excess from local parity breaking in baryon matter

We propose that local parity breaking induced by a large-scale fluctuation of topological charge at large temperatures and/or condensation of pseudoscalar mesons in the isotriplet channel for large baryon densities may be responsible for the substantial dilepton excess that is found for low invariant masses and moderate values of pT in central heavy ions collisions. This insofar unexplained enhancement could be understood by a combination of two effects leading to an excess of both e+e− and μ+μ− pairs with respect to theoretical predictions based on conventional hadronic processes: (a) a modification of the dispersion relation of photons and vector mesons propagating in such a nuclear medium due to local parity breaking; (b) the appearance of new decay channels, forbidden by parity conservation in QCD in the usual vacuum. Possible signatures of this effect and perspectives for its detection are discussed.

Second Thoughts about the <i>τ-θ</i> Puzzle

The new parity value of π0 was determined according to the hypothesis of conservation of particle number. The theo-retical pentaquark proton’s parity value was also determined, and it was found that the conservation of parity is account nicely for the τ-θ puzzle.

The effect of parity conservation on the spin–orbit conserving and spin–orbit changing differential cross sections for the inelastic scattering of NO(X) by Ar

The fully Λ-doublet resolved state-to-state differential cross sections (DCSs) for the collisions of NO(X, (2)Π, v = 0, j = 0.5) with Ar have been shown to depend sensitively on the conservation of the total parity of the NO molecular wavefunction. Parity changing collisions exhibit a single maximum only in the DCS, while parity conserving transitions exhibit multiple rainbow peaks. This behaviour is shown to arise directly from the constructive or destructive interference of collisions impacting on the two pointed ends and on the flatter middle of the NO molecule. A simple hard shell, four path model has been employed to determine the relative phase shifts of the paths contributing to the scattering amplitude. The model calculations using the V(sum) potential, together with the results of a quasi-quantum treatment, provide good qualitative agreement with the experimental spin-orbit conserving (ΔΩ = 0) DCSs, suggesting that the dynamics for all but the lowest Δj transitions are determined largely by the repulsive part of the potential. The collisions leading to spin-orbit changing transitions (ΔΩ = 1) have been also found to be dominated by repulsive forces, even for the lowest Δj values. However, they are less well reproduced by hard shell calculations, because of the crucial participation of the V(diff) potential in determining the outcome of these collisions.

Study of theη→π+π−π0decay in p − p collisions with WASA-at-COSY

Study of the η → π + π − π 0 decay allows for precise tests of the C parity conservation, makes possible to set constraints on the u and d as well as s and d quark mass ratios and can be used for a verification of the predictions of the Chiral Perturbation Theory (ChPT). The WASA-at-COSY collaboration has accumulated the world largest numbers of η mesons produced in p − d and p − p collisions. This report includes preliminary results of the ongoing analysis of the η → π + π − π 0 decay from p − p data which were collected during 8 weeks of the COSY beam time in 2010 in Forschungszentrum Julich with more than 10 8 η mesons produced.

Double differential cross sections of proton emission in neutron induced reaction on27Al

Double differential sections for proton emission on aluminium are presented for 40 MeV incident neutron energies. Angular distributions, energy differential and total production cross sections are obtained. The results are compared to existing data and to nuclear model calculations which include preequilibrium and compound decay mechanisms. The EMPIRE code treats these mechanisms in the framework of TUL model for multistep direct and NVWY model for multistep compound. The Hauser Feshbach theory is used to calculate emission from the compound nucleus, with a full conservation of spin and parity.

Three-vector correlation in statistical reactions: the role of the triatomic parity

This article presents a methodology for the determination of the k-j-k' three-vector correlation assuming a statistical model for atom-diatom reactions; k and k' are the reagent-approach and product-recoil directions, respectively, and j is the rotational angular momentum of the reagent diatomic. Although the polarization of reagent angular momentum is in most cases negligible, conservation of the triatomic parity imposes a certain polarization for some combinations involving low reagent and product rotational states. Statistical and quantum-mechanical polarization-dependent differential cross sections were calculated for the barrierless D(+) + H(2)(v = 0,j) → HD(v' = 0,j') + H(+) reaction. The agreement between the two is in most cases excellent, confirming the statistical character of the reaction at low and moderate collision energies.

Parity violation and parity conservation in unstirred crystallization: Effect of first crystals

AbstractStatistics of nucleation of chiral forms was studied to establish the effect of the number of first crystals and their handedness on distributions of enantiomers. Various bimodal, trimodal and unimodal distributions are obtained in unstirred crystallization, depending on the number of initial crystals and growth conditions. The binomial distribution satisfactorily describes experimental distributions of enantiomeric excess and may be used to predict distributions and probabilities of nucleation of enantiomers. The first nucleated crystals determine the handedness of secondary crystals, and number of initial crystals governs statistics of chiral nucleation. According to the binomial distribution if single crystals nucleate as the first, the bimodal distributions result with D and L peaks. If LD, LL, and DD pairs are nucleated as first, trimodal distributions with D, R, and L peaks are created, and if groups of crystals of various handedness nucleate as the first the unimodal distributions of enantiomeric excess with racemate R peaks are formed. Chiral nucleation experiments on sodium bromate were the basis for the theoretical considerations and verifications of predictions resulting from binomial distributions on probabilities of the creation of L and D crystals, and racemates, and the presence of D, L, and R peaks in the distributions. Growth conditions affect the number of the first crystals and effectiveness of cloning, and as a result, the distributions of enantiomers. Formation of pure enantiomers and/or racemates proves that the conservation of chiral symmetry, and the breakage of chiral symmetry can occur in unstirred crystallization. (© 2012 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)

Do high-energy neutrinos travel faster than photons in a discrete space–time?

The recent OPERA measurement of high-energy neutrino velocity, once independently verified, implies new physics in the neutrino sector. We revisit the theoretical inconsistency of the fundamental high-energy cutoff attributing to quantum gravity with the parity-violating gauge symmetry of local quantum field theory describing neutrinos. This inconsistency suggests high-dimension operators of neutrino interactions. Based on these studies, we try to view the OPERA result, high-energy neutrino oscillations and indicate to observe the restoration of parity conservation by measuring the asymmetry of high-energy neutrinos colliding with left- and right-handed polarized electrons.

Valley Blockade Quantum Switching in Silicon Nanostructures

In analogy to the Coulomb and the Pauli spin blockade, based on the electrostatic repulsion and the Pauli exclusion principle respectively, the concept of valley blockade in Silicon nanostructures is explored. The valley parity operator is defined. Valley blockade is determined by the parity conservation of valley composition eigenvectors in quantum transport. A Silicon quantum changeover switch based on a triple of donor quantum dots capable to separate electrons having opposite valley parity by virtue of the valley parity conservation is proposed. The quantum changeover switch represents a novel kind of hybrid quantum based classical logic device.

General positivity bounds for spin observables in single particle inclusive production

Positivity constraints, derived initially assuming parity conservation, for the inclusive reaction of the type $A(\mathrm{\text{spin}}1/2)+B(\mathrm{\text{spin}}1/2)\ensuremath{\rightarrow}C+X$, where the spins of both initial $\mathrm{\text{spin}}\mathrm{\text{\ensuremath{-}}}1/2$ particles can be in any possible directions and no polarization is observed in the final state, are generalized to the case of parity violation. By means of a systematic method, we obtain nontrivial bounds involving all the spin observables of the reaction and we discuss some relevant physics processes. Particularly, we discover a nontrivial positivity constraint for the processes $pp\ensuremath{\rightarrow}{W}^{\ifmmode\pm\else\textpm\fi{}}/{Z}^{0}+X$ or $pp\ensuremath{\rightarrow}{\ensuremath{\ell}}^{\ifmmode\pm\else\textpm\fi{}}+X$ where ${\ensuremath{\ell}}^{\ifmmode\pm\else\textpm\fi{}}$ decayed from ${W}^{\ifmmode\pm\else\textpm\fi{}}/{Z}^{0}$, which could be checked at the ongoing longitudinal spin program at Relativistic Heavy Ion Collider.

Unexpected effects in spin-polarized electron-impact excitation of the(3d104s5s)3S1state in zinc

Observations of the $(3{d}^{10}4{s}^{2}){}^{1}{S}_{0}\ensuremath{\rightarrow}(3{d}^{10}4s5s){}^{3}{S}_{1}$ excitation process in zinc, with incident spin-polarized electrons, show significant deviations from expectations for a pure electron exchange transition. This result, derived from values of up to 10% of the Stokes parameter ${P}_{2}$ (aligned linear polarization) of the light emitted in the $(3{d}^{10}4s5s){}^{3}{S}_{1}\ensuremath{\rightarrow}(3{d}^{10}4s4p){}^{3}{P}_{0,1,2}$ optical decays, is very different from predictions of near-zero values from general theory as well as sophisticated, relativistic close-coupling and distorted-wave numerical models. Although the linear light polarization ${P}_{2}$ may be nonzero by parity conservation, it was expected to vanish due to dynamical symmetries.

Perturbative renormalization factors andO(a2)corrections for lattice four-fermion operators with improved fermion/gluon actions

In this work we calculate the corrections to the amputated Green's functions of 4-fermion operators, in 1-loop Lattice Perturbation theory. One of the novel aspects of our calculations is that they are carried out to O(a^2) (a: lattice spacing). We employ the Wilson/clover action for massless fermions (also applicable for the twisted mass action in the chiral limit) and a family of Symanzik improved actions for gluons. Our calculations have been carried out in a general covariant gauge. Results have been obtained for several popular choices of values for the Symanzik coefficients. While our Green's function calculations regard any pointlike 4-fermion operators which do not mix with lower dimension ones, we pay particular attention to DF=2 operators, both Parity Conserving and Parity Violating (F: flavour). We compute the perturbative renormalization constants for a complete basis of 4-fermion operators and we study their mixing pattern. For some of the actions considered here, even O(a^0) results did not exist in the literature to date. The correction terms which we calculate are essential ingredients for minimizing the lattice artifacts which are present in non-perturbative evaluations of renormalization constants with the RI'-MOM method. Our perturbative results, for the matrix elements of DF=2 operators and for the corresponding renormalization matrices, depend on a large number of parameters: coupling constant, number of colors, lattice spacing, external momentum, clover parameter, Symanzik coefficients, gauge parameter. To make these results most easily accessible, we have included them in the distribution package of this paper, as an ASCII file named: 4-fermi.m; the file is best perused as Mathematica input. The main results of this work have been applied to improve non-perturbative estimates of the B_K-parameter in N_F=2 twisted mass lattice QCD.

Inequivalent solutions for Dirac spin-$\bf \frac{1}{2}\;$12 particles under conservation of parity II

By law of conservation of parity we show that Dirac equation in an electromagnetic field can be split up into two uncoupled two-component equations. As a result, we shall find twice as many as the conventional solutions. For free particles four linearly independent plane wave solutions which hold for E > 0 and also for E < 0 can be established. In a Coulomb field we shall easily find the stationary solutions.

Topological phases of one-dimensional fermions: An entanglement point of view

The effect of interactions on topological insulators and superconductors remains, to a large extent, an open problem. Here, we describe a framework for classifying phases of one-dimensional interacting fermions, focusing on spinless fermions with time-reversal symmetry and particle number parity conservation, using concepts of entanglement. In agreement with an example presented by Fidkowski \emph{et. al.} (Phys. Rev. B 81, 134509 (2010)), we find that in the presence of interactions there are only eight distinct phases, which obey a $\mathbb{Z}_8$ group structure. This is in contrast to the $\mathbb{Z}$ classification in the non-interacting case. Each of these eight phases is characterized by a unique set of bulk invariants, related to the transformation laws of its entanglement (Schmidt) eigenstates under symmetry operations, and has a characteristic degeneracy of its entanglement levels. If translational symmetry is present, the number of distinct phases increases to 16.

Search for the minimal universal extra dimension model at the LHC withs=7 TeV

Universal Extra Dimension (UED) model is one of the popular extension of the Standard Model (SM) which offers interesting phenomenology. In the minimal UED (mUED) model, Kaluza-Klein (KK) parity conservation ensures that $n=1$ KK states can only be pair produced at colliders and the lightest KK particle is stable. In most of the parameter space, first KK excitation of SM hypercharge gauge boson is the lightest one and it can be a viable dark matter candidate. Thus, the decay of $n=1$ KK particles will always involve missing transverse energy as well as leptons and jets. The production cross sections of $n=1$ KK particles are large and such particles may be observed at the Large Hadron Collider (LHC). We explore the mUED discovery potential of the LHC with $\sqrt{s}$ = 7 TeV in the multileptonic final states. Since in the early LHC run, precise determination of missing transverse energy may not be possible, we examine the LHC reach with and without using missing transverse energy information. We observe that missing transverse energy cut will not improve mUED discovery reach significantly. We have found that opposite sign di-lepton channel is the most promising discovery mode and with first $fb^{-1}$ of collected luminosity, LHC will be able to discover the strongly interacting $n=1$ KK particles with masses upto 800 to 900 GeV.

The energy levels of positron under molecules XH(X=O, S, Se and Te)and positronium

The present work devotes to the energy levels of positron under molecules XH(X=O, S, Se and Te)and the relations with nuclear field using Dirac equation based on the full symmetry group. Under these nuclear fields, the energy of positron is about e+=-1.022 MeV. For the lower energy level, the energy of positron is increased with nuclear field; for the higher energy level, the energy of positron is nearly invariant with nuclear field. In this case, it is the three-photon annihilation. The formation of the positronium is in orthopositronium 3S, excited state, followed the conservation of charge parity.

Cosmic positron and antiproton constraints on the gauge-Higgs dark matter

We calculate the cosmic raypositron and antiproton spectra of a gauge-Higgs dark matter candidatein a warped five-dimensional SO(5) × U(1) gauge-Higgsunification model. The stability of the gauge-Higgs boson isguaranteed by the H parity under which only the Higgs boson is oddat low energy. The 4-point vertices of HHW+W− and HHZZ, allowedby H parity conservation, have the same magnitude as in the standardmodel, which yields efficient annihilation rate for mH > mW. Themost dominant annihilation channel is HH → W+W− followed bythe subsequent decays of the W bosons into positrons or quarks,which undergo fragmentation into antiproton. Comparing with theobserved positron and antiproton spectra with the PAMALA andFermi/LAT, we found that the Higgs boson mass cannot be larger than 90 GeV, in order not to overrun the observations. Together with theconstraint on not overclosing the Universe, the valid range of thedark matter mass is restricted to 70–90 GeV.

Majorana fermion codes

We initiate the study of Majorana fermion codes (MFCs). These codes can be viewed as extensions of Kitaev's one-dimensional (1D) model of unpaired Majorana fermions in quantum wires to higher spatial dimensions and interacting fermions. The purpose of MFCs is to protect quantum information against low-weight fermionic errors, that is, operators acting on sufficiently small subsets of fermionic modes. We examine to what extent MFCs can surpass qubit stabilizer codes in terms of their stability properties. A general construction of 2D MFCs is proposed that combines topological protection based on a macroscopic code distance with protection based on fermionic parity conservation. Finally, we use MFCs to show how to transform any qubit stabilizer code to a weakly self-dual CSS code.

Topological quantum computation away from the ground state using Majorana fermions

We relax one of the requirements for topological quantum computation with Majorana fermions. Topological quantum computation was discussed so far as manipulation of the wave function within degenerate many-body ground state. The simplest particles providing degenerate ground state, Majorana fermions, often coexist with extremely low-energy excitations so keeping the system in the ground state may be hard. We show that the topological protection extends to the excited states, as long as the Majorana fermions do not interact neither directly nor via the excited states. This protection relies on the fermion parity conservation and so it is generic to any implementation of Majorana fermions.

Inequivalent solutions for Dirac spin-12 particles under conservation of parity I

Inequivalent invariance constraints upon solutions for Dirac spin-12 particles under conservation of space inversion, time reversal, and charge conjugation have been established, respectively, from standard representation. For space inversion we explicitly show that the wave functions for zero mass neutrinos satisfy only one constraint. For free particles we show that the conventional plane wave solutions as well as Foldy–Wouthuysen representation conditionally comply with the inversion constraints. As a result, only two positive energy solutions and two negative energy solutions can be established. Instead, by law of conservation of parity one shall obtain four linearly independent plane wave solutions which hold not only for positive energies but also for negative energies. We explicitly point out why conventional approach fails to obtain such result. In contrast with free particles one expects intuitively that in a Coulomb field, one can establish twice as many as conventional solutions. Indeed, one shall find easily from inversion constraints that additional linearly independent degenerate bound states have to be established. We present the explicit result.