Wed·Jun 21, 2017Wednesday·June 21, 2017

1. 01*

   Study of the weak annihilation contributions in charmless $B_s\to VV$ decays

   Qin Chang🇨🇳 · Xiao-Nan Li🇨🇳 · Xin-Qiang Li🇨🇳 · Jun-Feng Sun🇨🇳

   In this paper, in order to probe the spectator-scattering and weak annihilation contributions in charmless $B_s\to VV$ (where $V$ stands for a light vector meson) decays, we perform the ${\chi }^2$-analyses for the end-point parameters within the QCD factorization framework, under the constraints from the measured ${\bar{B}}_s\to$${\rho }^0\varphi$, $\varphi K^{\ast 0}$, $\varphi \varphi$ and $K^{\ast 0}{\bar{K}}^{\ast 0}$ decays. The fitted results indicate that the end-point parameters in the factorizable and nonfactorizable annihilation topologies are non-universal, which is also favored by the charmless $B\to PP$ and $PV$ (where $P$ stands for a light pseudo-scalar meson) decays observed in the previous work. Moreover, the abnormal polarization fractions $f_{L,\perp }({\bar{B}}_s\to K^{\ast 0}{\bar{K}}^{\ast 0})=(20.1\pm 7.0)\%,(58.4\pm 8.5)\%$ measured by the LHCb collaboration can be reconciled through the weak annihilation corrections. However, the branching ratio of ${\bar{B}}_s\to \varphi K^{\ast 0}$ decay exhibits a tension between the data and theoretical result, which dominates the contributions to ${\chi }_{\min }^2$ in the fits. Using the fitted end-point parameters, we update the theoretical results for the charmless $B_s\to VV$ decays, which will be further tested by the LHCb and Belle-II experiments in the near future.

   hep-phhep-exEPJC(2017)·14 citations
2. 02*

   The economical 3-3-1 model revisited

   P. V. Dong🇻🇳 · D. Q. Phong🇻🇳 · D. V. Soa🇻🇳 · N. C. Thao🇻🇳

   We show that the economical 3-3-1 model poses a very high new physics scale of the order of 1000~TeV due to the constraint on the flavor-changing neutral current. The implications of the model for neutrino masses, inflation, leptogenesis, and superheavy dark matter are newly recognized. Alternatively, we modify the model by rearranging the third quark generation differently from the first two quark generations, as well as changing the scalar sector. The resultant model now predicts a consistent new physics at TeV scale unlike the previous case and may be fully probed at the current colliders. Particularly, due to the minimal particle contents, the models under consideration manifestly accommodate dark matter candidates and neutrino masses, with novel and distinct production mechanisms. The large flavor-changing neutral currents that come from the ordinary and exotic quark mixings can be avoided due to the approximate $B-L$ symmetry.

   hep-phEPJC(2018)·11 citations
3. 03*

   Combining states without scale hierarchies with ordered parton showers

   Nadine Fischer🇦🇺 · Stefan Prestel🇺🇸

   We present a parameter-free scheme to combine fixed-order multi-jet results with parton-shower evolution. The scheme produces jet cross sections with leading-order accuracy in the complete phase space of multiple emissions, resumming large logarithms when appropriate, while not arbitrarily enforcing ordering on momentum configurations beyond the reach of the parton-shower evolution equation. This requires the development of a matrix-element correction scheme for complex phase-spaces including ordering conditions as well as a systematic scale-setting procedure for unordered phase-space points. The resulting algorithm does not require a merging-scale parameter. We implement the new method in the Vincia framework and compare to LHC data.

   hep-phEPJC(2017)·18 citations
4. 04*

   Relativistic corrections to light-cone distribution amplitudes of S-wave $B_c$ mesons and heavy quarkonia

   Wei Wang🇨🇳 · Ji Xu🇨🇳 · Deshan Yang🇨🇳 · Shuai Zhao🇨🇳

   In collinear factorization, light-cone distribution amplitudes (LCDAs) are key ingredients to calculate the production rate of a hadron in high energy exclusive processes. For a doubly-heavy meson system (such as $B_c,J/\psi ,{\rm Y}$ etc), the LCDAs contain perturbative scales that can be integrated out and then are re-factorized into products of perturbatively calculable distribution parts and non-relativistic QCD matrix elements. In this re-factorization scheme, the LCDAs are known at next-to-leading order in the strong coupling constant ${\alpha }_s$ and at leading order in the velocity expansion. In this work, we calculate the $\mathcal{O}(v^2)$ corrections to twist-2 LCDAs of S-wave $B_c$ mesons. These results are applicable to heavy quarkonia like ${\eta }_{c,b}$, $J/\psi$ and ${\rm Y}$ by setting $m_b=m_c$. We apply these relativistically corrected LCDAs to study their inverse moments and a few Gegenbauer moments which are important for phenomenological study. We point out that the relativistic corrections are sizable, and comparable with the next-to-leading order radiative corrections. These results for LCDAs are useful in future theoretical analyses of the productions of heavy quarkonia and $B_c$ mesons.

   hep-phJHEP(2017)·30 citations
5. 05*

   Parton model description of multiparticle azimuthal correlations in $pA$ collisions

   Kevin Dusling🇺🇸 · Mark Mace🇺🇸 · Raju Venugopalan🇺🇸

   In arXiv:1705.00745, an initial state "parton model" of quarks scattering off a dense nuclear target was shown to qualitatively reproduce the systematics of multiparticle azimuthal anisotropy cumulants measured in proton/deuteron-nucleus ($pA$) collisions at RHIC and the LHC. The systematics included i) the behavior of the four-particle cumulant $c_2\{4\}$, which generates a real four-particle second Fourier harmonic $v_2\{4\}$, ii) the ordering $v_2\{2\}>v_2\{4\}\approx v_2\{6\}\approx v_2\{8\}$ for two-, four-, six-, and eight-particle Fourier harmonics, iii) the behavior of so-called symmetric cumulants $\text{SC}(2,3)$ and $\text{SC}(2,4)$. These features of azimuthal multiparticle cumulants were previously interpreted as a signature of hydrodynamic flow; our results challenge this interpretation. We expand here upon our previous study and present further details and novel results on the saturation scale and transverse momentum ($p_{\perp }$) dependence of multiparticle azimuthal correlations. We find that the dependence of $v_2\{2\}$ and $v_2\{4\}$ on the number of color domains in the target varies with the $p_{\perp }$ window explored. We extend our prior discussion of symmetric cumulants and compute as yet unmeasured symmetric cumulants. We investigate the $N_c$ dependence of $v_2\{2\}$ and $v_2\{4\}$. We contrast our results, which include multiple scatterings of each quark off the target, to the Glasma graph approximation, where each quark suffers at most two gluon exchanges with the target. We find that coherent multiple scattering is essential to obtain a positive definite $v_2\{4\}$. We provide an algorithm to compute expectation values of arbitrary products of the "dipole" lightlike Wilson line correlators.

   hep-phnucl-exnucl-thPRD(2018)·79 citations
6. 06*

   Dynamical gluon mass in the instanton vacuum model

   M. Musakhanov🇺🇿 · O. Egamberdiev🇺🇿

   We are considering the modifications of gluon properties in Instanton Liquid Model (ILM) for the QCD vacuum. Re-scattering of a gluons on an instantons leads to the dynamical momentum-dependent gluon mass $M_g(q).$ First, we considered scalar "gluon", since there are no zero-modes problem and found its dynamical mass $M_s(q)$. At the typical phenomenological values of the average instanton size $\rho =1/3fm$ and average inter-instanton distance $R=1fm$ we got $M_s(0)=256MeV$. Further, we extended this approach to the real vector gluon with careful consideration of zero-modes and got $M_g^2(q)=2M_s^2(q).$ This modification of the gluon in the instanton media might be important for the heavy quarkonium physics at least.

   hep-phPLB(2018)·14 citations
7. 07*

   Non-perturbative quark, gluon and meson correlators of unquenched QCD

   Anton K. Cyrol🇩🇪 · Mario Mitter🇦🇹 · Jan M. Pawlowski🇩🇪 · Nils Strodthoff🇺🇸

   We present non-perturbative first-principle results for quark-, gluon- and meson $1$PI correlation functions of two-flavour Landau-gauge QCD in the vacuum. These correlation functions carry the full information about the theory. They are obtained by solving their Functional Renormalisation Group equations in a systematic vertex expansion, aiming at apparent convergence. This work represents a crucial prerequisite for quantitative first-principle studies of the QCD phase diagram and the hadron spectrum within this framework. In particular, we have computed the gluon, ghost, quark and scalar-pseudoscalar meson propagators, as well as gluon, ghost-gluon, quark-gluon, quark, quark-meson, and meson interactions. Our results stress the crucial importance of the quantitatively correct running of different vertices in the semi-perturbative regime for describing the phenomena and scales of confinement and spontaneous chiral symmetry breaking without phenomenological input.

   hep-phhep-lathep-thPRD(2018)·284 citations
8. 08*

   New quantum effects in relativistic magnetohydrodynamics

   Yuji Hirono🇺🇸 · Dmitri E. Kharzeev🇺🇸 · Yi Yin🇺🇸

   Chiral anomaly induces a new kind of macroscopic quantum behavior in relativistic magnetohydrodynamics, including the chiral magnetic effect. In this talk we present two new quantum effects present in fluids that contain charged chiral fermions: 1) the turbulent inverse cascade driven by the chiral anomaly; 2) quantized chiral magnetic current induced by the reconnections of magnetic flux. We also discuss the implications for the evolution of the quark-gluon plasma produced in heavy ion collisions.

   hep-phNPA(2017)·5 citations
9. 09*

   Phase structure of complete asymptotically free SU($N_c$) theories with quarks and scalar quarks

   Frederik F. Hansen🇩🇰 · Tadeusz Janowski🇩🇰 · Kasper Langaeble🇩🇰 · Robert B. Mann🇨🇦 · Francesco Sannino🇩🇰 · Tom G. Steele🇨🇦 · Zhi-Wei Wang🇩🇰

   We determine the phase diagram of complete asymptotically free SU($N_c$) gauge theories featuring $N_s$ complex scalars and $N_f$ Dirac quarks transforming according to the fundamental representation of the gauge group. The analysis is performed at the maximum known order in perturbation theory. We unveil a very rich dynamics and associated phase structure. Intriguingly we discover that the complete asymptotically free conditions guarantee that the infrared dynamics displays long distance conformality, and in a regime when perturbation theory is applicable. We conclude our analysis by determining the quantum corrected potential of the theory and summarising the possible patterns of radiative symmetry breaking. These theories are of potential phenomenological interest as either elementary or composite ultraviolet finite extensions of the Standard Model.

   hep-phhep-thPRD(2018)·37 citations
10. 10*

    Theoretical implications of recent heavy flavour measurements at the LHC

    Monika Blanke🇩🇪

    Recent measurements have revealed a number of intriguing deviations from the Standard Model predictions in $B$ meson decays, in particular in observables testing lepton flavour universality. We review their experimental status and theoretical description in terms of effective Hamiltonians. We also discuss possible new physics interpretations in terms of simplified models and summarise their status in view of the stringent constraints from flavour physics and high-$p_T$ collider searches.

    hep-phhep-ex1 citation
11. 11*

    ${ϵ}_K^{\prime }/{ϵ}_K$: Standard Model and Supersymmetry

    Ulrich Nierste🇩🇪

    I give a pedagogical introduction into flavour-changing neutral current interactions of kaons and their role to reveal or constrain physics beyond the Standard Model (SM). Then I discuss the measure ${ϵ}_K^{\prime }$ of direct CP violation in $K\to \pi \pi$ decays, which deviates from the SM prediction by $2.8\sigma$. A supersymmetric scenario with flavour mixing among left-handed squarks can accomodate the measured value of ${ϵ}_K^{\prime }$ even for very heavy sparticles, outside the reach of the LHC. The considered scenario employs mass splittings among the right-handed up and down squarks (to enhance ${ϵ}_K^{\prime }$) and a gluino which is heavier than the left-handed strange-down mixed squarks by at least a factor of 1.5 (to suppress excessive contribution to ${ϵ}_K$, the measure of indirect CP violation). The branching ratios of the rare decays $K^{+}\to {\pi }^{+}\nu \bar{\nu }$ and $K_L\to {\pi }^0\nu \bar{\nu }$, to be measured by the NA62 and KOTO-step2 experiments, respectively, are only moderately affected. These measurements have the capability to either falsify the model or to constrain the CP phase associated with strange-down squark mixing accurately.

    hep-ph1 citation
12. 12*

    Dark Gauge U(1) Symmetry for an Alternative Left-Right Model

    Corey Kownacki🇺🇸 · Ernest Ma🇺🇸 · Nicholas Pollard🇺🇸 · Oleg Popov🇺🇸 · Mohammadreza Zakeri🇺🇸

    An alternative left-right model of quarks and leptons, where the $SU(2{)}_R$ lepton doublet $(\nu ,l{)}_R$ is replaced with $(n,l{)}_R$ so that $n_R$ is not the Dirac mass partner of ${\nu }_L$, has been known since 1987. Previous versions assumed a global $U(1{)}_S$ symmetry to allow $n$ to be identified as a dark-matter fermion. We propose here a gauge extension by the addition of extra fermions to render the model free of gauge anomalies, and just one singlet scalar to break $U(1{)}_S$. This results in two layers of dark matter, one hidden behind the other.

    hep-phEPJC(2018)·13 citations
13. 13*

    $R_K$ anomalies and simplified limits on $Z^{\prime }$ models at the LHC

    R. Sekhar Chivukula🇺🇸 · Joshua Isaacson🇺🇸 · Kirtimaan A. Mohan🇺🇸 · Dipan Sengupta🇺🇸 · Elizabeth H. Simmons🇺🇸

    The LHCb collaboration has recently reported a 2.5 $\sigma$ discrepancy with respect to the predicted value in a test of lepton universality in the ratio $R_{K^{\ast }}=BR(B\to K^{\ast }{\mu }^{+}{\mu }^{-})/BR(B\to K^{\ast }{e}^{+}{e}^{-})$. Coupled with an earlier observation of a similar anomaly in $R_K$, this has generated significant excitement. A number of new physics scenarios have been proposed to explain the anomaly. In this work we consider simplified limits on $Z^{\prime }$ models from ATLAS and CMS searches for new resonances in dilepton and dijet modes, and we use the simplified limits variable $\zeta$ to correlate the results of the resonance and B-decay experiments. By examining minimal $Z^{\prime }$ models that can accomodate the observed LHCb results, we show that the high-mass resonance search results are begining to be sensitive to these models and that future results will be more informative.

    hep-phhep-exPRD(2017)·29 citations
14. 14*

    Prospects for discovering a neutrino line induced by dark matter annihilation

    Chaimae El Aisati🇧🇪 · Camilo Garcia-Cely🇩🇪 · Thomas Hambye🇧🇪 · Laurent Vanderheyden🇧🇪

    In the near future, neutrino telescopes are expected to improve their sensitivity to the flux of monochromatic neutrinos produced by dark matter (DM) in our galaxy. This is illustrated by a new limit on the corresponding cross section that we derive from public IceCube data. In this context, we study which DM models could produce an observable flux of monochromatic neutrinos from DM annihilations. To this end, we proceed in two steps. First, within a set of simple and minimal assumptions concerning the properties of the DM particle, we determine the models that could give rise to a significant annihilation into monochromatic neutrinos at the freeze-out epoch. The list of models turns out to be very limited as a result of various constraints, in particular direct detection and neutrino masses at loop level. Given the fact that, even if largely improved, the sensitivities will be far from reaching the thermal annihilation cross section soon, a signal could only be observed if the annihilation into neutrinos today is boosted with respect to the freeze-out epoch. This is why, in a second step, we analyze the possibility of having such a large enhancement from the Sommerfeld effect. For each scenario, we also compute the cross sections into other annihilation products and confront our results with experimental constraints. We find that, within our simple and minimal assumptions, the expectation to observe monochromatic neutrinos is only possible in very specific scenarios. Some will be confirmed or excluded in the near future because they predict signals slightly below the current experimental sensitivities. We also discuss how these prospects change by relaxing our assumptions as well as by considering other types of sharp spectral features. For the latter, we consider boxed-shaped and bremsstrahlung spectra and provide the corresponding limits from IceCube data.

    hep-phJCAP(2017)·56 citations
15. 15*

    Updated Constraints on Self-Interacting Dark Matter from Supernova 1987A

    Cameron Mahoney🇺🇸 · Adam K. Leibovich🇺🇸 · Andrew R. Zentner🇺🇸

    We revisit SN1987A constraints on light, hidden sector gauge bosons ("dark photons") that are coupled to the standard model through kinetic mixing with the photon. These constraints are realized because excessive bremsstrahlung radiation of the dark photon can lead to rapid cooling of the SN1987A progenitor core, in contradiction to the observed neutrinos from that event. The models we consider are of interest as phenomenological models of strongly self-interacting dark matter. We clarify several possible ambiguities in the literature and identify errors in prior analyses. We find constraints on the dark photon mixing parameter that are in rough agreement with the early estimates of Dent et al., but only because significant errors in their analyses fortuitously canceled. Our constraints are in good agreement with subsequent analyses by Rrapaj & Reddy and Hardy & Lasenby. We estimate the dark photon bremsstrahlung rate using one-pion exchange (OPE), while Rrapaj & Reddy use a soft radiation approximation (SRA) to exploit measured nuclear scattering cross sections. We find that the differences between mixing parameter constraints obtained through the OPE approximation or the SRA approximation are roughly a factor of $\sim 2-3$. Hardy & Laseby include plasma effects in their calculations finding significantly weaker constraints on dark photon mixing for dark photon masses below $\sim 10\mathrm{MeV}$. We do not consider plasma effects. Lastly, we point out that the properties of the SN1987A progenitor core remain somewhat uncertain and that this uncertainty alone causes uncertainty of at least a factor of $\sim 2-3$ in the excluded values of the dark photon mixing parameter. Further refinement of these estimates is unwarranted until either the interior of the SN1987A progenitor is more well understood or additional, large, and heretofore neglected effects, are identified.

    hep-phastro-ph.COPRD(2017)·40 citations
16. 16*

    Three-body Unitarity with Isobars Revisited

    M. Mai🇺🇸 · B. Hu🇺🇸 · M. Doring🇺🇸 · A. Pilloni🇺🇸 · A. Szczepaniak🇺🇸

    The particle exchange model of hadron interactions can be used to describe three-body scattering under the isobar assumption. In this study we start from the 3->3 scattering amplitude for spinless particles, which contains an isobar-spectator scattering amplitude. Using a Bethe-Salpeter Ansatz for the latter, we derive a relativistic three-dimensional scattering equation that manifestly fulfills three-body unitarity and two-body unitarity for the sub-amplitudes. This property holds for energies above breakup and also in the presence of resonances in the sub-amplitudes.

    ↳ nucl-thhep-phEPJA(2017)·110 citations
17. 17*

    Global Orientifolded Quivers with Inflation

    Michele Cicoli🇮🇹 · Iñaki García-Etxebarria🇩🇪 · Christoph Mayrhofer🇩🇪 · Fernando Quevedo🇮🇹 · Pramod Shukla🇮🇹 · Roberto Valandro🇮🇹

    We describe global embeddings of fractional D3 branes at orientifolded singularities in type IIB flux compactifications. We present an explicit Calabi-Yau example where the chiral visible sector lives on a local orientifolded quiver while non-perturbative effects, ${\alpha }^{\prime }$ corrections and a T-brane hidden sector lead to full closed string moduli stabilisation in a de Sitter vacuum. The same model can also successfully give rise to inflation driven by a del Pezzo divisor. Our model represents the first explicit Calabi-Yau example featuring both an inflationary and a chiral visible sector.

    ↳ hep-thastro-ph.COhep-phJHEP(2017)·82 citations
18. 18*

    Scattering processes and resonances from lattice QCD

    Raul A. Briceno🇺🇸 · Jozef J. Dudek🇺🇸 · Ross D. Young🇦🇺

    The vast majority of hadrons observed in nature are not stable under the strong interaction, rather they are resonances whose existence is deduced from enhancements in the energy dependence of scattering amplitudes. The study of hadron resonances offers a window into the workings of quantum chromodynamics (QCD) in the low-energy non-perturbative region, and in addition, many probes of the limits of the electroweak sector of the Standard Model consider processes which feature hadron resonances. From a theoretical standpoint, this is a challenging field: the same dynamics that binds quarks and gluons into hadron resonances also controls their decay into lighter hadrons, so a complete approach to QCD is required. Presently, lattice QCD is the only available tool that provides the required non-perturbative evaluation of hadron observables. In this article, we review progress in the study of few-hadron reactions in which resonances and bound-states appear using lattice QCD techniques. We describe the leading approach which takes advantage of the periodic finite spatial volume used in lattice QCD calculations to extract scattering amplitudes from the discrete spectrum of QCD eigenstates in a box. We explain how from explicit lattice QCD calculations, one can rigorously garner information about a variety of resonance properties, including their masses, widths, decay couplings, and form factors. The challenges which currently limit the field are discussed along with the steps being taken to resolve them.

    ↳ hep-lathep-phnucl-thRMP(2018)·421 citations
19. 19*

    Gravitational wave searches for ultralight bosons with LIGO and LISA

    Richard Brito🇩🇪 · Shrobana Ghosh🇺🇸 · Enrico Barausse🇫🇷 · Emanuele Berti🇺🇸 · Vitor Cardoso🇵🇹 · Irina Dvorkin🇫🇷 · Antoine Klein🇫🇷 · Paolo Pani🇮🇹

    Ultralight bosons can induce superradiant instabilities in spinning black holes, tapping their rotational energy to trigger the growth of a bosonic condensate. Possible observational imprints of these boson clouds include (i) direct detection of the nearly monochromatic (resolvable or stochastic) gravitational waves emitted by the condensate, and (ii) statistically significant evidence for the formation of "holes" at large spins in the spin versus mass plane (sometimes also referred to as "Regge plane") of astrophysical black holes. In this work, we focus on the prospects of LISA and LIGO detecting or constraining scalars with mass in the range $m_s\in [10^{-19},10^{-15}]$ eV and $m_s\in [10^{-14},10^{-11}]$ eV, respectively. Using astrophysical models of black-hole populations calibrated to observations and black-hole perturbation theory calculations of the gravitational emission, we find that, in optimistic scenarios, LIGO could observe a stochastic background of gravitational radiation in the range $m_s\in [2\times 10^{-13},10^{-12}]$ eV, and up to $10^4$ resolvable events in a $4$-year search if $m_s\sim 3\times 10^{-13}\mathrm{eV}$. LISA could observe a stochastic background for boson masses in the range $m_s\in [5\times 10^{-19},5\times 10^{-16}]$, and up to $\sim 10^3$ resolvable events in a $4$-year search if $m_s\sim 10^{-17}\mathrm{eV}$. LISA could further measure spins for black-hole binaries with component masses in the range $[10^3,10^7]M_{\odot }$, which is not probed by traditional spin-measurement techniques. A statistical analysis of the spin distribution of these binaries could either rule out scalar fields in the mass range $\sim [4\times 10^{-18},10^{-14}]$ eV, or measure $m_s$ with ten percent accuracy if light scalars in the mass range $\sim [10^{-17},10^{-13}]$ eV exist.

    ↳ gr-qcastro-ph.HEhep-phhep-thPRD(2017)·390 citations
20. 20*

    Two-nucleon emission in neutrino and electron scattering from nuclei: the modified convolution approximation

    I. Ruiz Simo🇪🇸 · J.E. Amaro🇪🇸 · M.B. Barbaro🇮🇹 · J.A. Caballero🇪🇸 · G.D. Megias🇪🇸 · T.W. Donnelly🇺🇸

    The theoretical formalism of inclusive lepton-nucleus scattering in the two-nucleon emission channel is discussed in the context of a simplified approach, the modified convolution approximation. This allows one to write the 2p2h responses of the relativistic Fermi gas as a folding integral of two 1p1h responses with the energies and momenta transferred to each nucleon. The idea behind this method is to introduce different average momenta for the two initial nucleons in the matrix elements of the two-body current, with the innovation that they depend on the transferred energies and momenta. This method treats exactly the two-body phase space kinematics, and reduces the formulae of the response functions from seven-dimensional integrals over momenta to much simpler three-dimensional ones. The applicability of the method is checked by comparing with the full results within a model of electroweak meson-exchange currents. The predictions are accurate enough, especially in the low-energy threshold region where the average momentum approximation works the best.

    ↳ nucl-thhep-phAnnals Phys.(2018)·14 citations
21. 21*

    Beyond integrability: Baryon-baryon backward scattering in the massive Gross-Neveu model

    Michael Thies🇩🇪

    Due to integrability, baryon-baryon scattering in the massless Gross-Neveu model at large N features only forward elastic scattering. A bare mass term breaks integrability and is therefore expected to induce backward elastic scattering as well as inelastic reactions. We confirm these expectations by a study of baryon-baryon scattering in the massive Gross-Neveu model near the non-relativistic limit. This restriction enables us to solve the time-dependent Hartree-Fock equations with controlled approximations, using a combination of analytical methods from an effective field theory and the numerical solution of partial differential equations.

    ↳ hep-thhep-phnlin.SInucl-thPRD(2017)·5 citations
22. 22*

    Scheme-Independent Calculations of Physical Quantities in an $\mathcal{N}=1$ Supersymmetric Gauge Theory

    Thomas A. Ryttov🇩🇰 · Robert Shrock🇺🇸

    We consider an asymptotically free, vectorial, $\mathcal{N}=1$ supersymmetric gauge theory with gauge group $G$ and $N_f$ pairs of chiral superfields in the respective representations $\mathcal{R}$ and $\bar{\mathcal{R}}$ of $G$, having an infrared fixed point (IRFP) of the renormalization group at ${\alpha }_{IR}$. We present exact results for the anomalous dimensions of various (gauge-invariant) composite chiral superfields ${\gamma }_{{\Phi }_{\mathrm{prod}}}$ at the IRFP and prove that these increase monotonically with decreasing $N_f$ in the non-Abelian Coulomb phase of the theory and that scheme-independent expansions for these anomalous dimensions as powers of an $N_f$-dependent variable, ${\Delta }_f$, exhibit monotonic and rapid convergence to the exact ${\gamma }_{{\Phi }_{\mathrm{prod}}}$ throughout this phase. We also present a scheme-independent calculation of the derivative of the beta function, $d\beta /d\alpha {|}_{\alpha ={\alpha }_{IR}}$, denoted ${\beta }_{IR}^{\prime }$, up to $O({\Delta }_f^3)$ for general $G$ and $\mathcal{R}$, and, for the case $G=\mathrm{SU}(N_c)$, $\mathcal{R}=F$, we give an analysis of the properties of ${\beta }_{IR}^{\prime }$ calculated to $O({\Delta }_f^4)$.

    ↳ hep-thhep-lathep-phPRD(2017)·22 citations
23. 23*

    Euclidean mirrors: enhanced vacuum decay from reflected instantons

    Ibrahim Akal🇩🇪 · Gudrid Moortgat-Pick🇩🇪

    We study the tunneling of virtual matter-antimatter pairs from the quantum vacuum in the presence of a spatially uniform, time-dependent electric background composed of a strong, slow field superimposed with a weak, rapid field. After analytic continuation to Euclidean spacetime, we obtain from the instanton equations two critical points. While one of them is the closing point of the instanton path, the other serves as an Euclidean mirror which reflects and squeezes the instanton. It is this reflection and shrinking which is responsible for an enormous enhancement of the vacuum pair production rate. We discuss how important features of two different mechanisms can be analysed and understood via such a rotation in the complex plane. a) Consistent with previous studies, we first discuss the standard assisted mechanism with a static strong field and certain weak fields with a distinct pole structure in order to show that the reflection takes place exactly at the poles. We also discuss the effect of possible sub-cycle structures. We extend this reflection picture then to weak fields which have no poles present and illustrate the effective reflections with explicit examples. An additional field strength dependence for the rate occurs in such cases. We analytically compute the characteristic threshold for the assisted mechanism given by the critical combined Keldysh parameter. We discuss significant differences between these two types of fields. For various backgrounds, we present the contributing instantons and perform analytical computations for the corresponding rates treating both fields nonperturbatively. b) In addition, we also study the case with a nonstatic strong field which gives rise to the assisted dynamical mechanism. For different strong field profiles we investigate the impact on the critical combined Keldysh parameter. [...]

    ↳ hep-thhep-phJ.Phys.G(2018)·10 citations
24. 24*

    Baryon-Baryon Interactions and Spin-Flavor Symmetry from Lattice Quantum Chromodynamics

    Michael L. Wagman🇺🇸 · Frank Winter🇺🇸 · Emmanuel Chang🇺🇸 · Zohreh Davoudi🇺🇸 · William Detmold🇺🇸 · Kostas Orginos🇺🇸 · Martin J. Savage🇺🇸 · Phiala E. Shanahan🇺🇸

    Lattice quantum chromodynamics is used to constrain the interactions of two octet baryons at the SU(3) flavor-symmetric point, with quark masses that are heavier than those in nature (equal to that of the physical strange quark mass and corresponding to a pion mass of $\approx 806\mathtt{MeV}$). Specifically, the S-wave scattering phase shifts of two-baryon systems at low energies are obtained with the application of Lüscher's formalism, mapping the energy eigenvalues of two interacting baryons in a finite volume to the two-particle scattering amplitudes below the relevant inelastic thresholds. The values of the leading-order low-energy scattering parameters in the irreducible representations of SU(3) are consistent with an approximate SU(6) spin-flavor symmetry in the nuclear and hypernuclear forces that is predicted in the large-$N_c$ limit of QCD. The two distinct SU(6)-invariant interactions between two baryons are constrained at this value of the quark masses, and their values indicate an approximate accidental SU(16) symmetry. The SU(3) irreducible representations containing the $NN({}^1{S}_0)$, $NN({}^3{S}_1)$ and $\frac{1}{\sqrt{2}}({\Xi }^{0}n+{\Xi }^{-}p)({}^3{S}_1)$ channels unambiguously exhibit a single bound state, while the irreducible representation containing the ${\Sigma }^{+}p({}^3{S}_1)$ channel exhibits a state that is consistent with either a bound state or a scattering state close to threshold. These results are in agreement with the previous conclusions of the NPLQCD collaboration regarding the existence of two-nucleon bound states at this value of the quark masses.

    ↳ hep-lathep-phnucl-thPRD(2017)·125 citations
25. 25*

    Constructing probability density function of net-proton multiplicity distributions using Pearson curve method

    Nirbhay Kumar Behera🇰🇷 · Min Jung Kweon🇰🇷

    The probability density functions of proton, anti-proton, and net-proton multiplicity distributions are constructed from the Beam Energy Scan results of the STAR experiment using the Pearson curve method. The constructed distributions of proton and anti-proton are compared with Poisson and Binomial distributions. The net-proton probability distributions are compared with Skellam distributions to study the O(4) criticality near the chiral crossover transition. The $C_6/C_2$ results estimated from the obtained PDFs are compared with Skellam and Binomial baselines for the Beam Energy Scan data. The current study shows some signatures of O(4) criticality, which can be further investigated by precision measurements of the cumulants and understanding the contribution of non-critical fluctuations to them. This study also provides a baseline for the higher-order cumulant measurement in the upcoming RHIC BES II program and future LHC run.

    ↳ nucl-exhep-exhep-phnucl-thEPJA(2022)·4 citations
26. 26*

    $R^2$ corrections to holographic Schwinger effect

    Zi-qiang Zhang🇨🇳 · Chong Ma🇨🇳 · De-fu Hou🇨🇳 · Gang Chen🇨🇳

    We study $R^2$ corrections to the holographic Schwinger effect in an AdS black hole background and a confining D3-brane background, respectively. The potential analysis for these backgrounds is presented. The critical values for the electric field are obtained. It is shown that for both backgrounds increasing the Gauss-Bonnet parameter the Schwinger effect is enhanced. Moreover, the results provide an estimate of how the Schwinger effect changes with the shear viscosity to entropy density ratio, $\eta /s$, at strong coupling.

    ↳ hep-thhep-phAnnals Phys.(2017)·6 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.