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We describe the critical temperature dependence on the pion mass and on the isospin chemical potential in remarkably good agreement with lattice data. Our framework incorporates explicit dependence on quark masses, isospin and baryonic chemical potentials for the case of two flavors through ingredients from well-known high-and low-energy theories.
The Dalitz-plot of the decay D{sup 0{yields}{pi}+{pi}-{pi}0} measured by the BABAR collaboration shows the structure of a final state having quantum numbers I{sup G}J{sup PC} = 0{sup -}0{sup --}. An isospin analysis of this Dalitz-plot finds that the fraction of the I = 0 contribution is about 96%. This high I = 0 contribution is unexpected because the weak interaction violates the isospin.
We study the phase diagram of two flavor dense QCD at finite isospin and baryon chemical potentials in the framework of Nambu-Jona-Lasinio model. The system undergoes a crossover from a Bose-Einstein condensate of charged pions to a BCS superfluid with condensed quark-antiquark Cooper pairs when {mu}{sub I} increases at {mu}{sub B} = 0, and a nonzero baryon chemical potential serves as a mismatch between the pairing species. We observe a gapless pion condensation phase near the quadruple point ({mu}{sub I},{mu}{sub B}) = (m{sub {pi}},M{sub N}-1.5m{sub {pi}}) where m{sub {pi}}, M{sub N} are the vacuum masses of pions and nucleons, respectively. At very large isospin chemical potential, {mu}{sub I}>6.36m{sub {pi}}, an inhomogeneous LOFF superfluid phase appears in a window of {mu}{sub B}. Between the gapless and the LOFF phases, the pion superfluid phase and the normal quark matter phase are connected by a first order phase transition.
Gamow-Teller (GT) transitions are mediated by the {sigma}{tau} operator. Owing to its simplicity and also its spin-isospin nature, GT transitions play key roles in the studies of nuclear structure as well as astro-nuclear processes. In violent neutrino-induced reactions at the core-collapse stage of type II supernovae, Gamow-Teller (GT) transitions starting from stable as well as unstable pf-shell nuclei play important roles. We study GT transitions starting from {sup 47}Ti in a high-resolution ({sup 3}He,t) charge-exchange reactions at 0 deg. and at an intermediate incident energy of 140 MeV/nucleon at Research Center for Nuclear Physics (RCNP), Osaka. Individual GT transitions up to high excitations were observed. Assuming the isospin symmetry for the strengths of T{sub z} = {+-}3/2{yields}{+-}1/2 analogous GT transitions, we can deduce the detailed strength distribution starting from mirror unstable nucleus {sup 47}Mn.
Momentum correlations in two-proton and other multi-body decays of light proton-rich nuclei are discussed. The variety of such decays are illustrated by a number of examples. The measured correlations for the ground state of {sup 6}Be are found to be consistent with the cluster-model calculations of Grigorenko et al. The ground state of {sup 8}C decays by two sequential steps of 3-body (two-proton) decay passing through the {sup 6}Be{sub g.s.} intermediate state. The isobaric analog of {sup 8}C in {sup 8}B undergoes two-proton decay to the isobaric analog state in {sup 6}Li. To the extent that isospin is conserved, this is a Goldansky-type decay, i.e. the isospin-allowed immediate state in {sup 7}Be is energetically forbidden. An excited state in {sup 10}C is found to have a {approx}50% four-body-decay branch where the protons have a strong diproton character.
Nuclear matrix elements M{sup 0ν} for neutrino less double beta decays (0νββ) are crucial for neutrino studies in 0νββ experiments. The neutrino mass to be studied is sensitive to M{sup 0ν}, while theoretical calculations for M{sup 0ν} are hard. Thus experimental studies of nuclear structures and single β matrix elements M{sub β} associated with 0νββ are useful to confirm and help the theoretical calculations. This reports briefly experimental methods and recent charge exchange reaction studies for M{sub β}. The single β elements for M{sup ±}(2{sup −}) associated with M{sup 0ν}(2{sup −}), which is the major component of M{sup 0ν}, are found to be reduced (quenched) much by the spin isospin correlation and the nuclear medium (non-nucleonic isobar) effect. The present result suggests that the spin isospin components of M{sup 0ν} is fairly reduced (quenched)
In this proceeding we present a study of the D*ρ system made by using the method of QCD sum rules. Considering isospin and spin projectors, we investigate the different configurations and obtain three D* mesons with isospin I = 1/2, spin S = 0, 1, 2 and with masses 2500±67 MeV, 2523±60 MeV, and 2439±119 MeV, respectively. The last state can be related to D{sub 2}{sup *} (2460) (spin 2) listed by the Particle Data Group, while one of the first two might be associated with D*(2640), whose spin-parity is unknown. In the case of I = 3/2 we also find evidences of three states with spin 0, 1 and 2, respectively, with masses 2467±82 MeV, 2420±128 MeV, and 2550±56 MeV.
Here we perform a systematic study to extract the information for colliding nuclear matter via symmetry energy and nucleon-nucleon cross section in the fragmentation of some asymmetric colliding nuclei (O{sup 16}+Br{sup 80,} {sup 84,} {sup 92}) in the energy range between 50-200 MeV/nucleon. The simulations are carried out using isospin-dependent quantum-molecular dynamics (IQMD) computational approach for central collisions. Our study reveals that fragmentation pattern of neutron-rich colliding nuclei is sensitive to symmetry energy at lower incident energies, whereas isospin dependence of nucleon-nucleon cross section becomes dominant for reactions at higher incident energies.
We summarize a recent work (N. Sandulescu et al, arXiv:1507.04144) on isoscalar and isovector proton-neutron pairing treated in a formalism which conserves exactly the particle number and the isospin. The formalism is designed for self-conjugate (N=Z) systems of nucleons moving in an axially deformed mean field and interacting through the most general isovector and isoscalar pairing interactions. The ground state of these systems is described by a superposition of two types of condensates, i.e., condensates of isovector quartets, built by two isovector pairs coupled to the total isospin T=0, and condensates of isoscalar proton-neutron pairs. The comparison with the exact solutions of realistic isovector-isoscalar pairing Hamiltonians shows that this formalism is able to describe accurately the pairing correlations energies. It is also shown that, contrary to the majority of HFB calculations, in the present formalism the isovector and isoscalar pairing correlations coexist together for any pairing interactions.
A new momentum-space formulation for scattering of two spin-half particles, both either identical or unidentical, is formulated. As basis states the free linear-momentum states are not expanded into the angular-momentum states, the system’s spin states are described by the product of the spin states of the two particles, and the system’s isospin states by the total isospin states of the two particles. We evaluate the Lippmann-Schwinger equations for the T-matrix elements in these basis states. The azimuthal behavior of the potential and of the T-matrix elements leads to a set of coupled integral equations for the T-matrix elements in two variables only, which are the magnitude of the relative momentum and the scattering angle. Some symmetry relations for the potential and the T-matrix elements reduce the number of the integral equations to be solved. A set of six spin operators to express any interaction of two spin-half particles is introduced. We show the spin-averaged differential cross section as being calculated in terms of the solution of the set of the integral equations.
Considering a 3 + 1 dimensional lattice quantum chromodynamics (QCD) model defined with the improved Wilson action, three flavors, and 4 × 4 Dirac spin matrices, in the strong coupling regime, we reanalyze the question of the existence of the eightfold way baryons and complete our previous work where the existence of isospin octet baryons was rigorously solved. Here, we show the existence of isospin decuplet baryons which are associated with isolated dispersion curves in the subspace of the underlying quantum mechanical Hilbert space with vectors constructed with an odd number of fermion and antifermion basic quark and antiquark fields. Moreover, smoothness properties for these curves are obtained. The present work deals with a case for which the traditional method to solve the implicit equation for the dispersion curves, based on the use of the analytic implicit function theorem, cannot be applied. We do not have only one but two solutions for each one-baryon decuplet sector with fixed spin third component. Instead, we apply the Weierstrass preparation theorem, which also provides a general method for the general degenerate case. This work is completed by analyzing a spectral representation for the two-baryon correlations and providing the leading behaviors of the field strength normalization and the mass of the spectral contributions with more than one-particle. These are needed results for a rigorous analysis of the two-baryon and meson-baryon particle spectra.
We discuss the characteristic collider signatures, in particular a highly polarized resonant single-top channel for a minimal color triplet extension to the Standard Model. This extension provides baryogensis and a non-thermal production history of a dark matter candidate. We further discuss the implementation of both completely left and right-handed chiral interaction in the model and the difference in phenomenology between the two scenarios. If the color triplets are isospin singlets, the dark matter candidate mass is 1 GeV and the single-top quarks are strictly right-handed polarized. Alternatively, the isospin-doublet color triplets lead to strictly left-handed single top events and a more extended particle spectrum.
Recently the CRESST collaboration has published the long anticipated results of their direct Dark Matter (DM) detection experiment with a CaWO{sub 4} target. The number of observed events exceeds known backgrounds at more than 4σ significance, and this excess could potentially be due to DM scattering. We confront this interpretation with null results from other direct detection experiments for a number of theoretical models, and find that consistency is achieved in non-minimal models such as inelastic DM and isospin-violating DM. In both cases mild tension with constraints remain. The CRESST data can, however, not be reconciled with the null results and with the positive signals from DAMA and CoGeNT simultaneously in any of the models we study.
We extend the halo-independent method of Fox, Liu, and Weiner to include energy resolution and efficiency with arbitrary energy dependence, making it more suitable for experiments to use in presenting their results. Then we compare measurements and upper limits on the direct detection of low mass ( ∼ 10 GeV) weakly interacting massive particles with spin-independent interactions, including the upper limit on the annual modulation amplitude from the CDMS collaboration. We find that isospin-symmetric couplings are severely constrained both by XENON100 and CDMS bounds, and that isospin-violating couplings are still possible at the lowest energies, while the tension of the higher energy CoGeNT bins with the CDMS modulation constraint remains. We find the CRESST-II signal is not compatible with the modulation signals of DAMA and CoGeNT.
We study the solar capture rate of inelastic dark matter with endothermic and/or exothermic interactions. By assuming that an inelastic dark matter signal will be observed in next generation direct detection experiments we can set a lower bound on the capture rate that is independent of the local dark matter density, the velocity distribution, the galactic escape velocity as well as the scattering cross section. In combination with upper limits from neutrino observatories we can place upper bounds on the annihilation channels leading to neutrinos. We find that, while endothermic scattering limits are weak in the isospin-conserving case, strong bounds may be set for exothermic interactions, in particular in the spin-dependent case. Furthermore, we study the implications of observing two direct detection signals, in which case one can halo-independently obtain the dark matter mass and the mass splitting, and disentangle the endothermic/exothermic nature of the scattering. Finally we discuss isospin violation.
Minimal Dark Matter (MDM) is a theoretical framework highly appreciated for its minimality and yet its predictivity. Of the two only viable candidates singled out in the original analysis, the scalar eptaplet has been found to decay too quickly to be around today, while the fermionic quintuplet is now being probed by indirect Dark Matter (DM) searches. It is therefore timely to critically review the MDM paradigm, possibly pointing out generalizations of this framework. We propose and explore two distinct directions. One is to abandon the assumption of DM electric neutrality in favor of absolutely stable, millicharged DM candidates which are part of SU(2){sub L} multiplets with integer isospin. Another possibility is to lower the cutoff of the model, which was originally fixed at the Planck scale, to allow for DM decays. We find new viable MDM candidates and study their phenomenology in detail.
We study the dark matter (DM) direct detection for the models with the effects of the isospin-violating couplings, exothermic scatterings, and/or the lightness of the mediator, proposed to relax the tension between the CDMS-Si signals and null experiments. In the light of the new updates of the LUX and CDMSlite data, we find that many of the previous proposals are now ruled out, including the Ge-phobic exothermic DM model and the Xe-phobic DM one with a light mediator. We also examine the exothermic DM models with a light mediator but without the isospin violation, and we are unable to identify any available parameter space that could simultaneously satisfy all the experiments. The only models that can partially relax the inconsistencies are the Xe-phobic exothermic DM models with or without a light mediator. But even in this case, a large portion of the CDMS-Si regions of interest has been constrained by the LUX and SuperCDMS data.
Nuclear effective interactions are useful tools in astrophysical applications especially if one can guide the extrapolations to the extremes regions of isospin and density that are required to simulate dense, neutron-rich systems. Isospin extrapolations may be constrained in the laboratory by measuring the neutron skin thickness of a heavy nucleus, such as {sup 208}Pb. Similarly, future observations of massive neutron stars will constrain the extrapolations to the high-density domain. In this contribution we introduce a new relativistic effective interaction that is simultaneously constrained by the properties of finite nuclei, their collective excitations, and neutron-star properties. By adjusting two of the empirical parameters of the theory, one can efficiently tune the neutron skin thickness of {sup 208}Pb and the maximum neutron-star mass. We illustrate this procedure in response to the recent interpretation of x-ray observations by Steiner, Lattimer, and Brown that suggests that the FSUGold effective interaction predicts neutron-star radii that are too large and a maximum stellar mass that is too small. The new effective interaction is fitted to a neutron skin thickness in {sup 208}Pb of only R{sub n}-R{sub p}=0.16 fm and yields a moderately large maximum neutron-star mass of 1.94 M{sub {center_dot}}.