Wed·Aug 22, 2018Wednesday·August 22, 2018

1. 01*

   Towards solving the proton spin puzzle

   Andreas Ekstedt🇸🇪 · Hazhar Ghaderi🇸🇪 · Gunnar Ingelman🇸🇪 · Stefan Leupold (Uppsala University)🇸🇪

   The fact that the spins of the quarks in the proton, as measured in deep inelastic lepton scattering, only add up to about 30$\%$ of the spin of the proton is still not understood after 30 years. We show that our newly developed model for the quark and gluon momentum distributions in the proton, based on quantum fluctuations of the proton into baryon-meson pairs convoluted with Gaussian momentum distributions of partons in hadrons, can essentially reproduce the data on the proton spin structure function $g_1^P(x)$ and the associated spin asymmetry. A further improved description of the data is achieved by also including the relativistic correction of the Melosh transformation to the light-front formalism used in deep inelastic scattering. However, this does not fully resolve the spin puzzle, including also the neutron spin structure and the spin sum rules. These aspects can also be accounted for by our few-parameter model if the conventional SU(6) flavor-spin symmetry is broken, giving new information on the non-perturbative bound-state nucleon.

   hep-ph2 citations
2. 02*

   Correlating the anomalous results in $b\to s$ decays with inert Higgs doublet dark matter and muon $(g-2)$

   Basabendu Barman🇮🇳 · Debasish Borah🇮🇳 · Lopamudra Mukherjee🇮🇳 · Soumitra Nandi🇮🇳

   In this article, we have considered an extension of the inert Higgs doublet model with $SU(2{)}_L$ singlet vector like fermions. Our model is capable of addressing some interesting anomalous results in $b\to s{\ell }^{+}{\ell }^{-}$ decays (like $R(K^{(\ast )})$) and in muon $(g-2)$. Apart from explaining these anomalies, and being consistent with other flavour data, the model satisfies relevant constraints in the dark matter sector, while remaining within the reach of ongoing direct detection experiments. The model also produces signatures at the large hadron collider (LHC) with final states comprised of dilepton, dijet and missing energy, providing signals to be probed at higher luminosity.

   hep-phhep-exPRD(2019)·68 citations
3. 03*

   Colour Reconnection from Soft Gluon Evolution

   Stefan Gieseke🇩🇪 · Patrick Kirchgaeßer🇩🇪 · Simon Plätzer🇦🇹 · Andrzej Siodmok🇵🇱

   We consider soft gluon evolution at the amplitude level to expose the structure of colour reconnection from a perturbative point of view. Considering the cluster hadronization model and an universal Ansatz for the soft anomalous dimension we find strong support for geometric models considered earlier. We also show how reconnection into baryonic systems arises, and how larger cluster systems evolve. Our results provide the dynamic basis for a new class of colour reconnection models for cluster hadronization.

   hep-phJHEP(2018)·38 citations
4. 04*

   Double charged heavy constituents of dark atoms and superheavy nuclear objects

   Vakhid A. Gani🇷🇺 · Maxim Yu. Khlopov🇷🇺 · Dmitry N. Voskresensky🇷🇺

   We consider the model of composite dark matter assuming stable particles of charge $-2$ bound with primordial helium nuclei by Coulomb force in $O$He atoms. We study capture of such dark atoms in matter and propose a possibility of existence of stable $O$-enriched superheavy nuclei and $O$-nuclearites, in which heavy $O$-dark matter fermions are bound by electromagnetic forces with ordinary nuclear matter. $O$He atoms accumulation in stars and its possible effect in stellar evolution is also considered, extending the set of indirect probes for composite dark matter.

   hep-phastro-ph.COnucl-thPRD(2019)·21 citations
5. 05*

   Study of Anomalies in Exclusive Semileptonic B Decays

   Vincenzo Afferrante🇦🇹 · Guido Martinelli🇮🇹

   Our Vcb extraction is based on recent Belle results, with unfolded kinematical dependence. We use two different parameterizations of the form factors, the CLN and BGL parameterizations. We discuss how the known discrepancy between the inclusive and exclusive determinations of Vcb depends on an underestimate of the uncertainty with parameterizations that use heavy quark expansion. We investigate the results of the semileptonic B decay with heavy leptons (tau) compared to the decays into light leptons. Experimental ratio of the two branching ratios is systematically larger than the Standard Model(SM) prediction. Effects of new physics operators on the data about these decays are studied.

   hep-phPoS(2018)·0 citations
6. 06*

   Further study on the textures of neutrino mass matrix for maximal atmospherical mixing angle and Dirac CP phase

   Zhi-Cheng Liu🇨🇳 · Chong-Xing Yue🇨🇳 · Zhen-hua Zhao🇨🇳

   In this paper, we derive in a novel approach the possible textures of neutrino mass matrix that can lead to maximal atmospherical mixing angle (${\theta }_{23}^{}=\pi /4$) and Dirac CP phase ($\delta =-\pi /2$) in two phenomenologically appealing scenarios: (1) one neutrino mass matrix element being vanishing (2) one neutrino mass being vanishing. For the obtained textures, some neutrino mass sum rules which relate the neutrino masses and mixing parameters will emerge. With the help of these sum rules, the unknown absolute neutrino mass scale and Majorana CP phases can be determined. Some discussions about the possible textures of neutrino mass matrix that can lead to ${\theta }_{23}^{}=\pi /4$, $\delta =-\pi /2$ and maximal Majorana CP phases ($\rho ,\sigma =\pi /4$ or $3\pi /4$) as well as the model realization and breakings of the obtained textures are also given.

   hep-phPRD(2019)·7 citations
7. 07*

   Hyperfine structure of S-states in muonic ions of lithium, beryllium and boron

   A.E. Dorokhov🇷🇺 · A.A. Krutov🇷🇺 · A.P. Martynenko🇷🇺 · F.A. Martynenko🇷🇺 · O.S. Sukhorukova🇷🇺

   We make precise calculation of hyperfine structure of $S$-states in muonic ions of lithium, beryllium and boron in quantum electrodynamics. Corrections of orders ${\alpha }^5$ and ${\alpha }^6$ due to the vacuum polarization, nuclear structure and recoil in first and second orders of perturbation theory are taken into account. We obtain estimates of the total values of hyperfine splittings which can be used for a comparison with future experimental data.

   hep-phphysics.atom-phPRA(2018)·12 citations
8. 08*

   Strange and non-strange distributions from the collider data

   S. Alekhin🇩🇪 · J. Bluemlein🇩🇪 · S. Kulagin🇷🇺 · S.-O. Moch🇩🇪 · R. Petti🇺🇸

   We check the stability of the ABMP16 fit with respect to modifications of quark PDFs suggested in the recent literature: the strange sea enhancement and a positive non-vanishing $d/u$ ratio at $x\to 1$. These possibilities are examined using test versions of the ABMP16 PDF fit which demonstrate no need of those changes. Furthermore, we localize peculiar features in other analyses which are responsible for a different behaviour of the PDFs obtained. The strange sea enhancement can be explained by a choice of the PDF shapes being not flexible enough and therefore leading to an over-suppressed $d$-quark distribution. This suppression has to be compensated by a corresponding rise by the $s$-quark distribution. As a result, an unusually large strange sea suppression factor is obtained. The non-vanishing value of $d/u{|}_{x=1}$ becomes consistent with zero in case the higher-order QCD corrections to the DØ $W$-asymmetry data, which drive its value, are taken into account. Furthermore, the related $e$-asymmetry sample prefers a slightly negative value of $d/u{|}_{x=1}$, although it is consistent with zero. These clarifications support confidence in the PDF shapes used in the ABMP16 analyses.

   hep-phhep-exPoS(2018)·9 citations
9. 09*

   Electric current induced by an external magnetic field in the presence of electroweak matter

   Maxim Dvornikov (IZMIRAN, Tomsk State University)🇷🇺

   We study the generation of an electric current, along the external magnetic field, of fermions, interacting by parity violating electroweak forces with background matter. First, we discuss the situation of massive particles with nonzero anomalous magnetic moments. We show that the induced current is vanishing for such particles in the state of equilibrium. Then, the case of massless fermions is studied. We demonstrate that the contribution of the electroweak interaction is washed out from the expression for the current, which turns out to coincide with the prediction of the chiral magnetic effect. Our results are compared with findings of other authors.

   hep-phhep-thEPJ Web Conf.(2018)·8 citations
10. 10*

    A multiquark approach to excited hadrons and Regge trajectories

    S. S. Afonin🇷🇺

    We propose a novel approach to construction of hadron spectroscopy. The case of light nonstrange mesons is considered. By assumption, all such mesons above 1 GeV appear due to creation of constituent quark-antiquark pairs inside the pi or rho (omega) mesons. These spin-singlet or triplet pairs dictate the quantum numbers of formed resonance. The resulting classification of light mesons turns out to be in a better agreement with the experimental observations than the standard quark model classification. It is argued that the total energy of quark components should be proportional to the hadron mass squared rather than the linear mass. As a byproduct a certain relation expressing the constituent quark mass via the gluon and quark condensate is put forward. We show that our approach leads to an effective mass counting scheme for meson spectrum and results in the linear Regge and radial Regge trajectories by construction. An experimental observation of these trajectories might thus serve as an evidence not for string but for multiquark structure of highly excited hadrons.

    hep-phnucl-thAdv.High Energy Phys.(2019)·7 citations
11. 11*

    SMASH -- A new hadronic transport approach

    Hannah Petersen🇩🇪 · Dmytro Oliinychenko🇺🇸 · Markus Mayer🇩🇪 · Jan Staudenmaier🇩🇪 · Sangwook Ryu🇩🇪

    Microscopic transport approaches are the tool to describe the non-equilibrium evolution in low energy collisions as well as in the late dilute stages of high-energy collisions. Here, a newly developed hadronic transport approach, SMASH (Simulating Many Accelerated Strongly-interacting Hadrons) is introduced. The overall bulk dynamics in low energy heavy ion collisions is shown including the excitation function of elliptic flow employing several equations of state. The implications of this new approach for dilepton production are discussed and preliminary results for afterburner calculations at the highest RHIC energy are presented and compared to previous UrQMD results. A detailed understanding of a hadron gas with vacuum properties is required to establish the baseline for the exploration of the transition to the quark-gluon plasma in heavy ion collisions at high net baryon densities.

    ↳ nucl-thhep-phnucl-exNPA(2019)·46 citations
12. 12*

    QCD phase diagram in a magnetic background for different values of the pion mass

    Massimo D'Elia🇮🇹 · Floriano Manigrasso🇮🇹 · Francesco Negro🇮🇹 · Francesco Sanfilippo🇮🇹

    We investigate the behavior of the pseudo-critical temperature of $N_f=2+1$ QCD as a function of a static magnetic background field for different values of the pion mass, going up to $m_{\pi }\simeq 660$ MeV. The study is performed by lattice QCD simulations, adopting a stout staggered discretization of the theory on lattices with $N_t=6$ slices in the Euclidean temporal direction; for each value of the pion mass the temperature is changed moving along a line of constant physics. We find that the decrease of $T_c$ as a function of $B$, which is observed for physical quark masses, persists in the whole explored mass range, even if the relative variation of $T_c$ appears to be a decreasing function of $m_{\pi }$, approaching zero in the quenched limit. The location of $T_c$ is based on the renormalized quark condensate and its susceptibility; determinations based on the Polyakov loop lead to compatible results. On the contrary, inverse magnetic catalysis, i.e. the decrease of the quark condensate as a function of $B$ in some temperature range around $T_c$, is not observed when the pion mass is high enough. That supports the idea that inverse magnetic catalysis might be a secondary phenomenon, while the modifications induced by the magnetic background on the gauge field distribution and on the confining properties of the medium could play a primary role in the whole range of pion masses

    ↳ hep-lathep-phhep-thPRD(2018)·114 citations
13. 13*

    Anisotropic hydrodynamics with number-conserving kernels

    D. Almaalol🇺🇸 · M. Alqahtani🇸🇦 · M. Strickland🇺🇸

    We compare anisotropic hydrodynamics (aHydro) results obtained using the relaxation-time approximation (RTA) and leading-order (LO) scalar \lambda \phi^4 collisional kernels. We extend previous work by explicitly enforcing number conservation through the incorporation of a dynamical chemical potential (fugacity) in the underlying aHydro distribution function. We focus on the case of a transversally homogenous and boost-invariant system obeying classical statistics and compare the relevant moments of the two collisional kernels. We then compare the time evolution of the aHydro microscopic parameters and components of the energy-momentum tensor. We also determine the non-equilibrium attractor using both the RTA and LO conformal \lambda \phi^4 number-conserving kernels. We find that the aHydro dynamics receives quantitatively important corrections when enforcing number conservation, however, the aHydro attractor itself is not modified substantially.

    ↳ nucl-thhep-phPRC(2019)·16 citations
14. 14*

    $\mathcal{C}\mathcal{P}$ Violation from String Theory

    Hans Peter Nilles🇩🇪 · Michael Ratz🇺🇸 · Andreas Trautner🇩🇪 · Patrick K.S. Vaudrevange🇩🇪

    We identify a natural way to embed $\mathcal{C}\mathcal{P}$ symmetry and its violation in string theory. The $\mathcal{C}\mathcal{P}$ symmetry of the low energy effective theory is broken by the presence of heavy string modes. $\mathcal{C}\mathcal{P}$ violation is the result of an interplay of $\mathcal{C}\mathcal{P}$ and flavor symmetry. $\mathcal{C}\mathcal{P}$ violating decays of the heavy modes could originate a cosmological matter-antimatter asymmetry.

    ↳ hep-thhep-phPLB(2018)·32 citations

* Reconstructed cohort: no mailing for this day survives in the archive. Papers are grouped by their submission times and arXiv's announcement cut-off, assuming announcement without delay; positions follow identifier order. Validated at ~91% exact-day agreement against the archived era.