Mon·Sep 18, 2017Monday·September 18, 2017

1. 01*

   Strong decays of exotic and non-exotic heavy baryons in the chiral quark-soliton model

   Hyun-Chul Kim🇰🇷 · Maxim V. Polyakov🇷🇺 · Michal Praszalowicz🇵🇱 · Ghil-Seok Yang🇰🇷

   In the large $N_c$ limit both heavy and light baryons are described by the universal mean field, which allows us to relate the properties of heavy baryons to light ones. With the only input from the decays of light octet baryons (due to the universality of the chiral mean field), excellent description of strong decays of both charm and bottom sextets is obtained. The parameter-free prediction for the widths of exotic anti-decapentaplet ($\overline{15}$) baryons is also made. The exotic heavy baryons should be anomalously narrow despite of large phase space available. In particular, the widths of ${\Omega }_c(3050)$ and ${\Omega }_c(3119)$, interpreted as members of $\overline{15}$-plet, are very small: 0.48~MeV and 1.12~MeV respectivly. This result is in very good agreement with the measurements of the LHCb Collaboration and provides natural and parameter free explanation of the LHCb observation that ${\Omega }_c(3050)$ and ${\Omega }_c(3119)$ have anomalously small widths among five recently observed states.

   hep-phPRD(2017)·54 citations
2. 02*

   Matching the Quasi Parton Distribution in a Momentum Subtraction Scheme

   Iain W. Stewart🇺🇸 · Yong Zhao🇺🇸

   The quasi parton distribution is a spatial correlation of quarks or gluons along the $z$ direction in a moving nucleon which enables direct lattice calculations of parton distribution functions. It can be defined with a nonperturbative renormalization in a regularization independent momentum subtraction scheme (RI/MOM), which can then be perturbatively related to the collinear parton distribution in the $\overline{\text{MS}}$ scheme. Here we carry out a direct matching from the RI/MOM scheme for the quasi-PDF to the $\overline{\text{MS}}$ PDF, determining the non-singlet quark matching coefficient at next-to-leading order in perturbation theory. We find that the RI/MOM matching coefficient is insensitive to the ultraviolet region of convolution integral, exhibits improved perturbative convergence when converting between the quasi-PDF and PDF, and is consistent with a quasi-PDF that vanishes in the unphysical region as the proton momentum $P^z\to \infty$, unlike other schemes. This direct approach therefore has the potential to improve the accuracy for converting quasi-distribution lattice calculations to collinear distributions.

   hep-phhep-latnucl-thPRD(2018)·154 citations
3. 03*

   Colour unwound - disentangling colours for azimuthal asymmetries in Drell-Yan scattering

   Daniël Boer🇳🇱 · Tom van Daal🇳🇱 · Jonathan R. Gaunt🇳🇱 · Tomas Kasemets🇳🇱 · Piet J. Mulders🇳🇱

   It has been suggested that a colour-entanglement effect exists in the Drell-Yan cross section for the 'double T-odd' contributions at low transverse momentum $Q_T$, rendering the colour structure different from that predicted by the usual factorisation formula [1]. These T-odd contributions can come from the Boer-Mulders or Sivers transverse momentum dependent distribution functions. The different colour structure should be visible already at the lowest possible order that gives a contribution to the double Boer-Mulders (dBM) or double Sivers (dS) effect, that is at the level of two gluon exchanges. To discriminate between the different predictions, we compute the leading-power contribution to the low-$Q_T$ dBM cross section at the two-gluon exchange order in the context of a spectator model. The computation is performed using a method of regions analysis with Collins subtraction terms implemented. The results conform with the predictions of the factorisation formula. In the cancellation of the colour entanglement, diagrams containing the three-gluon vertex are essential. Furthermore, the Glauber region turns out to play an important role - in fact, it is possible to assign the full contribution to the dBM cross section at the given order to the region in which the two gluons have Glauber scaling. A similar disentanglement of colour is found for the dS effect.

   hep-phSciPost Phys.(2017)·8 citations
4. 04*

   Global analysis of color fluctuation effects in proton- and deuteron-nucleus collisions at RHIC and the LHC

   Massimiliano Alvioli🇮🇹 · Leonid Frankfurt🇮🇱 · Dennis Perepelitsa🇺🇸 · Mark Strikman🇺🇸

   We test the hypothesis that configurations of a proton with a large-$x$ parton, $x_p\gtrsim 0.1$, have a smaller than average size. The QCD $Q^2$ evolution equations suggest that these small configurations also have a significantly smaller interaction strength, which has observable consequences in collisions with nuclei. We perform a global analysis of jet production data in proton- and deuteron-nucleus collisions at RHIC and the LHC. Using a model which takes a distribution of interaction strengths into account, we quantitatively extract the $x_p$-dependence of the average interaction strength, $\sigma (x_p)$, over a wide kinematic range. By comparing the RHIC and LHC results, our analysis finds that the interaction strength for small configurations, while suppressed, grows faster with collision energy than does that for average configurations. We check that this energy dependence is consistent with the results of a method which, given $\sigma (x_p)$ at one energy, can be used to quantitatively predict that at another. This finding further suggests that at even lower energies, nucleons with a large-$x_p$ parton should interact much more weakly than those in an average configuration, a phenomenon in line with explanations of the EMC effect for large-$x_p$ quarks in nuclei based on color screening.

   hep-phhep-exnucl-exPRD(2018)·38 citations
5. 05*

   Octet Baryons in Large Magnetic Fields

   Amol Deshmukh🇺🇸 · Brian C. Tiburzi🇺🇸

   Magnetic properties of octet baryons are investigated within the framework of chiral perturbation theory. Utilizing a power counting for large magnetic fields, the Landau levels of charged mesons are treated exactly giving rise to baryon energies that depend non-analytically on the strength of the magnetic field. In the small-field limit, baryon magnetic moments and polarizabilities emerge from the calculated energies. We argue that the magnetic polarizabilities of hyperons provide a testing ground for potentially large contributions from decuplet pole diagrams. In external magnetic fields, such contributions manifest themselves through decuplet-octet mixing, for which possible results are compared in a few scenarios. These scenarios can be tested with lattice QCD calculations of the octet baryon energies in magnetic fields.

   hep-phhep-latnucl-thPRD(2018)·22 citations
6. 06*

   $J/\psi$ $\to$ $D_{s,d}\pi$, $D_{s,d}K$ decays with perturbative QCD approach

   Junfeng Sun🇨🇳 · Yueling Yang🇨🇳 · Jie Gao🇨🇳 · Qin Chang🇨🇳 · Jinshu Huang🇨🇳 · Gongru Lu🇨🇳

   Besides the conventional strong and electromagnetic decay modes, the $J/\psi$ particle can also decay via the weak interaction in the standard model. In this paper, nonleptonic $J/\psi$ $\to$ $D_{s,d}\pi$, $D_{s,d}K$ weak decays, corresponding to the externally emitted virtual $W$ boson process, are investigated with the perturbative QCD approach. It is found that branching ratio for the Cabibbo-favored $J/\psi$ $\to$ $D_s\pi$ decay can reach up to $\mathcal{O}(10^{-10})$, which might be potentially measurable at the future high-luminosity experiments.

   hep-phhep-exPRD(2016)·5 citations
7. 07*

   ${\rm Y}(nS)$ $\to$ $B_c^{\ast }D$ decays with perturbative QCD approach

   Yueling Yang🇨🇳 · Junfeng Sun🇨🇳 · Jinshu Huang🇨🇳 · Haiyan Li🇨🇳 · Gongru Lu🇨🇳 · Qin Chang🇨🇳

   The ${\rm Y}(nS)$ $\to$ $B_c^{\ast }D$ weak decays ($n$ $=$ $1$, $2$, $3$) are investigated with perturbative QCD approach. It is found that the CKM-favored ${\rm Y}(nS)$ $\to$ $B_c^{\ast }{D}_s$ decays have branching ratio of $\mathcal{O}(10^{-10})$, which might be potentially accessible to the future LHC and SuperKEKB experiments.

   hep-phhep-exInt.J.Mod.Phys.A(2016)·5 citations
8. 08*

   Flavor anomalies from warped space

   Eugenio Megias🇪🇸 · Mariano Quiros🇪🇸 · Lindber Salas🇪🇸

   We study the recently found anomalies in $B$-meson decays within a scenario with a warped extra dimension where the Standard Model fermions are propagating in the bulk. The anomalies are then interpreted as the result of the exchange of heavy vector resonances with electroweak quantum numbers. The model naturally leads to lepton-flavor universality violation when different flavor fermions are differently localized along the extra dimension, signaling a different degree of compositeness in the dual holographic theory.

   hep-phhep-thNucl.Part.Phys.Proc.(2018)·2 citations
9. 09*

   Pion Polarizability Status Report

   Murray Moinester🇮🇱

   The electric ${\alpha }_{\pi }$ and magnetic ${\beta }_{\pi }$ charged pion Compton polarizabilities are of fundamental interest in the low-energy sector of quantum chromodynamics (QCD).They are directly linked to the phenomenon of spontaneously broken chiral symmetry within QCD and to the dynamics of the pion-photon interaction.The combination (${\alpha }_{\pi }-{\beta }_{\pi }$) was measured by:(1) CERN COMPASS via radiative pion Primakoff scattering (Bremsstrahlung) in the nuclear Coulomb field, ${\pi }^{-}Z\to {\pi }^{-}Z\gamma$, (2) SLAC PEP Mark-II via two-photon production of pion pairs, $\gamma \gamma \to {\pi }^{+}{\pi }^{-}$, and (3) Mainz Microtron via radiative pion photoproduction from the proton, $\gamma p\to \gamma {\pi }^{+}n$. COMPASS and Mark-II agree with one another:(1) ${\alpha }_{\pi }-{\beta }_{\pi }=4.0\times 10^{-4}f{m}^3$, (2) ${\alpha }_{\pi }-{\beta }_{\pi }=4.4\times 10^{-4}f{m}^3$. The Mainz value (3) ${\alpha }_{\pi }-{\beta }_{\pi }=11.6\times 10^{-4}f{m}^3$ is excluded here because a dispersion relations calculation using the Mainz value as input gives significantly too large $\gamma \gamma \to {\pi }^0{\pi }^0$ cross sections compared to DESY Crystal Ball data. COMPASS and Mark-II values agree well with the two-loop chiral perturbation theory ChPT prediction ${\alpha }_{\pi }-{\beta }_{\pi }=5.7\times 10^{-4}f{m}^3$, thereby strengthening the identification of the pion with the Goldstone boson of QCD.

   hep-phhep-ex1 citation
10. 10*

    Photoproduction with a mini-jet model and Cosmic Ray showers

    Fernando Cornet🇪🇸 · Carlos Garcia-Canal🇦🇷 · Agnes Grau🇪🇸 · Giulia Pancheri🇮🇹 · Sergio J. Sciutto🇦🇷

    We present post-LHC updates of estimates of the total photo-production cross section in a mini-jet model with infrared soft gluon resummation, and apply the model to study Cosmic Ray shower development, comparing the results with those obtained from other existing models.

    hep-phCERN Proc.(2018)·0 citations
11. 11*

    Holographic model for charmonium dissociation

    Nelson R. F. Braga🇧🇷 · Luiz F. Ferreira🇧🇷 · Alfredo Vega🇨🇱

    We present a holographic bottom up model for the thermal behavior of $c\bar{c}$ vector mesons in a finite temperature and density plasma. There is a clear physical interpretation for the three imput energy parameters of the model. Two of them are related to the mass spectrum of the heavy meson. Namely the quark mass and the string tension of the quark anti-quark interaction. The third parameter is a large energy scale associated with the non-hadronic meson decay. In such a process the heavy meson is transformed into a much lighter state by electroweak processes. The corresponding transition amplitude is assumed to depend on the enegy scale associated with this large mass variation. With this three parameter model one can fit the masses and decay constants of $J/\Psi$ and three radial excitations with an rms error of 20.7 %. Using the geometry of a charged black hole, one finds the spectral function for charmonium states inside a plasma at finite temperature and density. The charmonium dissociation in the medium is represented by the decrease in the height of the spectral function peaks.

    hep-phhep-thPLB(2017)·62 citations
12. 12*

    Resonant absorption of bosonic dark matter in molecules

    Asimina Arvanitaki🇨🇦 · Savas Dimopoulos🇺🇸 · Ken Van Tilburg🇺🇸

    We propose a new class of bosonic dark matter (DM) detectors based on resonant absorption onto a gas of small polyatomic molecules. Bosonic DM acts on the molecules as a narrow-band perturbation, like an intense but weakly coupled laser. The excited molecules emit the absorbed energy into fluorescence photons that are picked up by sensitive photodetectors with low dark count rates. This setup is sensitive to any DM candidate that couples to electrons, photons, and nuclei, and may improve on current searches by several orders of magnitude in coupling for DM masses between 0.2 eV and 20 eV. This type of detector has excellent intrinsic energy resolution, along with several control variables---pressure, temperature, external electromagnetic fields, molecular species/isotopes---that allow for powerful background rejection methods as well as precision studies of a potential DM signal. The proposed experiment does not require usage of novel exotic materials or futuristic technologies, relying instead on the well-established field of molecular spectroscopy, and on recent advances in single-photon detection. Cooperative radiation effects, which arise due to the large spatial coherence of the nonrelativistic DM field in certain detector geometries, can tightly focus the DM-induced fluorescence photons in a direction that depends on the DM's velocity, possibly permitting a detailed reconstruction of the full 3D velocity distribution in our Galactic neighborhood, as well as further background rejection.

    hep-phhep-thphysics.atom-phphysics.opticsPRX(2018)·146 citations
13. 13*

    Electromagnetic fields in small systems from a multiphase transport model

    Xin-Li Zhao🇨🇳 · Yu-Gang Ma🇨🇳 · Guo-Liang Ma🇨🇳

    We calculate the electromagnetic fields generated in small systems by using 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 energies available at the BNL Relativistic Heavy Ion Collider and in $p$+Pb collisions at energies available at the CERN Large Hadron Collider. We study the centrality dependencies and the spatial distributions of electromagnetic fields. We further investigate the azimuthal fluctuations of the magnetic field and its correlation with the fluctuating geometry using event-by-event simulations. We find that the azimuthal correlation $⟨\cos 2({\Psi }_B-{\Psi }_2)⟩$ between the magnetic field direction and the second harmonic participant plane is almost zero in small systems with high multiplicities, but not in those with low multiplicities. This indicates that the charge azimuthal correlation, $⟨\cos ({\varphi }_{\alpha }+{\varphi }_{\beta }-2{\Psi }_{RP})⟩$, is not a valid probe to study the chiral magnetic effect (CME) in small systems with high multiplicities. However, we suggest searching for possible CME effects in small systems with low multiplicities.

    hep-phnucl-exnucl-thPRC(2018)·28 citations
14. 14*

    Pions as Gluons in Higher Dimensions

    Clifford Cheung🇺🇸 · Grant N. Remmen🇺🇸 · Chia-Hsien Shen🇺🇸 · Congkao Wen🇺🇸

    We derive the nonlinear sigma model as a peculiar dimensional reduction of Yang-Mills theory. In this framework, pions are reformulated as higher-dimensional gluons arranged in a kinematic configuration that only probes cubic interactions. This procedure yields a purely cubic action for the nonlinear sigma model which exhibits a symmetry enforcing color-kinematics duality. Remarkably, the associated kinematic algebra originates directly from the Poincare algebra in higher dimensions. Applying the same construction to gravity yields a new quartic action for Born-Infeld theory and, applied once more, a cubic action for the special Galileon theory. Since the nonlinear sigma model and special Galileon are subtly encoded in the cubic sectors of Yang-Mills theory and gravity, respectively, their double copy relationship is automatic.

    ↳ hep-thgr-qchep-phJHEP(2018)·80 citations
15. 15*

    $e^{+}$ and $\bar{p}$ production in $pp$ collisions and the cosmic-ray $e^{+}/\bar{p}$ flux ratio

    Kfir Blum🇮🇱 · Ryosuke Sato🇮🇱 · Masahiro Takimoto🇯🇵

    Secondary astrophysical production of $e^{+}$ and $\bar{p}$ cosmic rays is considered. Inclusive $\pi$, $K$, and $\bar{p}$ production cross sections in $pp$ collisions at large $\sqrt{s}$ are parametrised using recent experimental data at LHC energies. The astrophysical production rate ratio $Q_{e^{+}}/Q_{\bar{p}}$ is calculated for an input cosmic ray proton flux consistent with local measurements. At $10<E<100$$\sim$GeV the cosmic ray flux ratio $J_{e^{+}}/J_{\bar{p}}$ measured by AMS02 falls below the production rate ratio by about 50\%, while at high energy $E>100$$\sim$GeV the measured flux ratio coincides with the production rate ratio of the secondary source.

    ↳ astro-ph.HEhep-exhep-phPRD(2018)·14 citations
16. 16*

    Photon sector analysis of Super and Lorentz symmetry breaking: effective photon mass, bi-refringence and dissipation

    Luca Bonetti🇫🇷 · Luís R. dos Santos Filho🇧🇷 · José A. Helayël-Neto🇧🇷 · Alessandro D. A. M. Spallicci🇫🇷

    Within the Standard Model Extension (SME), we expand our previous findings on four classes of violations of Super-Symmetry (SuSy) and Lorentz Symmetry (LoSy), differing in the handedness of the Charge conjugation-Parity-Time reversal (CPT) symmetry and in whether considering the impact of photinos on photon propagation. The violations, occurring at the early universe high energies, show visible traces at present in the Dispersion Relations (DRs). For the CPT-odd classes ($V_{\mu }$ breaking vector) associated with the Carroll-Field-Jackiw (CFJ) model, the DRs and the Lagrangian show for the photon an effective mass, gauge invariant, proportional to $|\vec{V}|$. The group velocity exhibits a classic dependency on the inverse of the frequency squared. For the CPT-even classes ($k_F$ breaking tensor), when the photino is considered, the DRs display also a massive behaviour inversely proportional to a coefficient in the Lagrangian and to a term linearly dependent on $k_F$. All DRs display an angular dependence and lack LoSy invariance. In describing our results, we also point out the following properties: i) the appearance of complex or simply imaginary frequencies and super-luminal speeds and ii) the emergence of bi-refringence. Finally, we point out the circumstances for which SuSy and LoSy breakings, possibly in presence of an external field, lead to the non-conservation of the photon energy-momentum tensor. We do so for both CPT sectors.

    ↳ hep-thastro-ph.COgr-qchep-phEPJC(2018)·38 citations
17. 17*

    Soft pion theorem, asymptotic symmetry and new memory effect

    Yuta Hamada🇯🇵 · Sotaro Sugishita🇯🇵

    It is known that soft photon and graviton theorems can be regarded as the Ward-Takahashi identities of asymptotic symmetries. In this paper, we consider soft theorem for pions, i.e., Nambu-Goldstone bosons associated with a spontaneously broken axial symmetry. The soft pion theorem is written as the Ward-Takahashi identities of the $S$-matrix under asymptotic transformations. We investigate the asymptotic dynamics, and find that the conservation of charges generating the asymptotic transformations can be interpreted as a pion memory effect.

    ↳ hep-thgr-qchep-phJHEP(2017)·43 citations
18. 18*

    Four-loop critical exponents for the Gross-Neveu-Yukawa models

    Nikolai Zerf🇩🇪 · Luminita N. Mihaila🇩🇪 · Peter Marquard🇩🇪 · Igor F. Herbut🇨🇦 · Michael M. Scherer🇩🇪

    We study the chiral Ising, the chiral XY and the chiral Heisenberg models at four-loop order with the perturbative renormalization group in $4-ϵ$ dimensions and compute critical exponents for the Gross-Neveu-Yukawa fixed points to order $\mathcal{O}({ϵ}^4)$. Further, we provide Padé estimates for the correlation length exponent, the boson and fermion anomalous dimension as well as the leading correction to scaling exponent in 2+1 dimensions. We also confirm the emergence of supersymmetric field theories at four loops for the chiral Ising and the chiral XY models with $N=1/4$ and $N=1/2$ fermions, respectively. Furthermore, applications of our results relevant to various quantum transitions in the context of Dirac and Weyl semimetals are discussed, including interaction-induced transitions in graphene and surface states of topological insulators.

    ↳ hep-thcond-mat.str-elhep-phPRD(2017)·186 citations
19. 19*

    Dark matter scenarios with multiple spin-2 fields

    N.L. Gonzalez Albornoz🇩🇪 · Angnis Schmidt-May🇩🇪 · Mikael von Strauss🇸🇪

    We study ghost-free multimetric theories for $(N+1)$ tensor fields with a coupling to matter and maximal global symmetry group $S_N\times (Z_2{)}^N$. Their mass spectra contain a massless mode, the graviton, and $N$ massive spin-2 modes. One of the massive modes is distinct by being the heaviest, the remaining $(N-1)$ massive modes are simply identical copies of each other. All relevant physics can therefore be understood from the case $N=2$. Focussing on this case, we compute the full perturbative action up to cubic order and derive several features that hold to all orders in perturbation theory. The lighter massive mode does not couple to matter and neither of the massive modes decay into massless gravitons. We propose the lighter massive particle as a candidate for dark matter and investigate its phenomenology in the parameter region where the matter coupling is dominated by the massless graviton. The relic density of massive spin-2 can originate from a freeze-in mechanism or from gravitational particle production, giving rise to two different dark matter scenarios. The allowed parameter regions are very different from those in scenarios with only one massive spin-2 field and more accessible to experiments.

    ↳ hep-thastro-ph.COgr-qchep-phJCAP(2018)·41 citations
20. 20*

    Relating Quark Confinement and Chiral Symmetry Breaking in QCD

    Hideo Suganuma (1) · Takahiro M. Doi (2) · Krzysztof Redlich · Chihiro Sasaki (3) ((1) Kyoto U. · (2) RIKEN · (3) Wroclaw U.)

    We study the relation between quark confinement and chiral symmetry breaking in QCD. Using lattice QCD formalism, we analytically express the various "confinement indicators", such as the Polyakov loop, its fluctuations, the Wilson loop, the inter-quark potential and the string tension, in terms of the Dirac eigenmodes. In the Dirac spectral representation, there appears a power of the Dirac eigenvalue ${\lambda }_n$ such as ${\lambda }_n^{N_t-1}$, which behaves as a reduction factor for small ${\lambda }_n$. Consequently, since this reduction factor cannot be cancelled, the low-lying Dirac eigenmodes give negligibly small contribution to the confinement quantities,while they are essential for chiral symmetry breaking. These relations indicate no direct, one-to-one correspondence between confinement and chiral symmetry breaking in QCD. In other words, there is some independence of quark confinement from chiral symmetry breaking, which can generally lead to different transition temperatures/densities for deconfinement and chiral restoration. We also investigate the Polyakov loop in terms of the eigenmodes of the Wilson, the clover and the domain-wall fermion kernels, respectively, and find the similar results. The independence of quark confinement from chiral symmetry breaking seems to be natural, because confinement is realized independently of quark masses and heavy quarks are also confined even without the chiral symmetry.

    ↳ hep-lathep-phhep-thnucl-thJ.Phys.G(2017)·25 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.