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Published: 2017-09-19T20:30:00-05:00
The dynamical diquark picture asserts that exotic hadrons can be formed from widely separated colored diquark or triquark components. We use the Born-Oppenheimer (BO) approximation to study the spectrum of states thus constructed, both in the basis of diquark spins and in the basis of heavy quark-antiquark spins. We develop a compact notation for naming these states, and use the results of lattice simulations for hybrid mesons to predict the lowest expected BO potentials for both tetraquarks and pentaquarks. We then compare to the set of exotic candidates with experimentally determined quantum numbers, and find that all of them can be accommodated. Once decay modes are also considered, one can develop selection rules of both exact ($J^{PC}$ conservation) and approximate (within the context of the BO approximation) types and test their effectiveness. We find that the most appealing way to satisfy both sets of selection rules requires including additional low-lying BO potentials, a hypothesis that can be checked on the lattice.
Neutron drops confined in an external field are studied in the framework of relativistic Brueckner-Hartree-Fock theory using the bare nucleon-nucleon interaction. A strong influence of the tensor forces on the evolution of spin-orbit splittings with neutron number is found. This result provides interesting insight for neutron rich systems and forms an important guide for future microscopic derivations of nuclear energy density functionals.
We evaluate the transport properties such as shear viscosity ($\eta$), bulk viscosity ($\zeta$) and their ratios over entropy density ($s$) for hadronic matter using relativistic non-extensive Boltzmann transport equation (NBTE) in relaxation time approximation (RTA). In NBTE, we argue that the system far from equilibrium may not reach to an equilibrium described by extensive (Boltzmann-Gibbs (BG)) statistics but to a $q$-equilibrium defined by Tsallis non-extensive statistics after subsequent evolution, where $q$ denotes the degree of non-extensivity. We observe that $\eta/s$ and $\zeta/s$ initially decrease rapidly with the temperature ($T$) for various $q$-values while they become independent of $q$ at higher $T$. As $q$ increases, the magnitudes of $\eta/s$ and $\zeta/s$ increase in the lower temperature region. We also show the upper mass cutoff dependence of these ratios for a particular $q$ and find that they decrease with the increase in mass cutoff of hadrons. Further, we present the first estimation of isothermal compressibility ($\kappa_T$) using non-extensive Tsallis statistics at finite baryon chemical potential ($\mu_B$). It is observed that, $\kappa_T$ changes significantly with the degree of non-extensivity. We also study the squared speed of sound ($c_{s}^{2}$) as a function of temperature at finite baryon chemical potential for various $q$ and upper mass cutoff. It is noticed that there is a strong impact of $q$ and mass cutoff on the behaviour of $c_{s}^{2}$.
Elliptic flow in heavy-ion collisions is an important signature of a possible de-confinement transition from hadronic phase to partonic phase. In the present work, we use non-extensive statistics, which has been used for transverse momentum ($p_{\rm T}$) distribution in proton+proton ($p+p$) collisions, as the initial particle distribution function in Boltzmann Transport Equation (BTE). A Boltzmann-Gibbs Blast Wave (BGBW) function is taken as an equilibrium function to get the final distribution to describe the particle production in heavy-ion collisions. In this formalism, we try to estimate the elliptic flow in Pb+Pb collisions at $\sqrt{s_{\rm NN}}$ = 2.76 TeV at the LHC for different centralities. The elliptic flow ($v_2$) of identified particles seems to be described quite well in the available $p_{\rm T}$ range. An approach, which combines the non-extensive nature of particle production in $p+p$ collisions through an evolution in kinetic theory using BTE, with BGBW equilibrium distribution is successful in describing the spectra and elliptic flow in heavy-ion collisions.
The production mechanism of quarkonia states in hadronic collisions is still
to be understood by the scientific community. In high-multiplicity $p+p$
collisions, Underlying Event (UE) observables are of major interest. The
Multi-Parton Interactions (MPI) is a UE observable, where several interactions
occur at the partonic level in a single $p+p$ event. This leads to dependence
of particle production on event multiplicity. If the MPI occurs in a harder
scale, there will be a correlation between the yield of quarkonia and total
charged particle multiplicity. The ALICE experiment at the Large Hadron
Collider (LHC) in $p+p$ collisions at $\sqrt{s}$ = 7 and 13 TeV has observed an
approximate linear increase of relative $J/\psi$ yield
($\frac{dN_{J/\psi}/dy}{
We provide an accurate evaluation of the two-photon exchange correction to the hyperfine splitting of S energy levels in muonic hydrogen exploiting the corresponding measurements in electronic hydrogen. The proton structure uncertainty in the calculation of $\alpha^5$ contribution is reduced from $100~\mathrm{ppm}$ level to $16~\mathrm{ppm}$.
The binding system of a hadron and a nucleus is a topic of great interest for investigating the hadron properties. In the heavy-flavor region, the attraction between a $P(=\bar{D},B)$ meson and a nucleon $N$ can appear, where the $PN-P^\ast N$ mixing plays an important role in relation to the heavy-quark spin symmetry. The attraction can produce exotic heavy mesic nuclei that are stable against the strong decay. We study an exotic system where the $\bar{D}$ ($B$) meson and nucleus are bound. The meson-nucleus interaction is given by a folding potential with single-channel $PN$ interaction and the nucleon number distribution function. By solving the Schr\"odinger equations of the heavy meson and the nucleus, we obtain several bound and resonant states for nucleon number $A=16,\dots,208$. The results indicate the possible existence of exotic mesic nuclei with a heavy antiquark.
Present nuclear detection techniques prevents us from determining if the analogue of a Rydberg molecule exists for the nuclear case. But nothing in nature disallows their existence. As in the atomic case, Rydberg nuclear molecules would be a laboratory for new aspects and applications of nuclear physics. We propose that Rydberg nuclear molecules, which represent the exotic, halo nuclei version, such as 11Be + 11Be, of the well known quasimolecules observed in stable nuclei such as 12C + 12C, might be common structures that could manifest their existence along the dripline. A study of possible candidates and the expected structure of such exotic clustering of two halo nuclei: the Rydberg nuclear molecules, is made on the basis of three diferent methods. It is shown that such cluster structures might be stable and unexpectedly common.
We formulate a set of mass relations for the baryon octet and decuplet with positive and negative parity in terms of the order parameter of QCD chiral symmetry. The Gell-Mann--Okubo mass formula and Gell-Mann's equal spacing rule hold manifestly in this approach. Thermal masses of the baryons are calculated in the mean field approximation for various pion masses, and the results are compared with the recent lattice studies. A general trend of the nucleon, $\Delta$ and $\Omega$ parity-doublers seen in the available lattice data can be understood qualitatively. Expected mass modifications of other strange baryons are also given with the physical and heavier pion masses.
The liquid drop model of 2-flavored ($u$ and $d$) nucleus is well known and successful, analogically, a similar drop model for 3-flavored ($u$, $d$ and $s$) nucleus is developed. A 3-flavored nucleus conjectured could be stable only if its baryon number is lager than a critical one, $A_{\rm c}$, in which strangeons are the constituent as an analogy of nucleons for nucleus. We try to model strangeon matter in a sense of phenomenological liquid drop, with two free parameters: the mass per bayron of a strangeon in vacuum, $M$, and potential deep between strangeons, $\epsilon$. It is found that, for $M\sim$ GeV and $\epsilon\sim 100$ MeV, strangeon matter could be stable and its critical number could be as low as $A_{\rm c}=300$.
We calculate the electromagnetic fields generated in small systems by using
the a multiphase transport (AMPT) model. Compared to A+A collisions, we find
that the absolute electric and magnetic fields are not small in p+Au and d+Au
collisions at RHIC energy and in p+Pb collisions at the LHC energy. We study
the centrality dependences and the spatial distributions of electromagnetic
fields. We further investigate the azimuthal fluctuations of magnetic field and
its correlation with the fluctuating geometry using event-by-event simulations.
We find that the azimuthal correlation $