Tue·Aug 6, 2019Tuesday·August 6, 2019

1. 01*

   Nonperturbative Dynamics of Hadronic Collisions

   Mateus Broilo

   In the last couple of years, the LHC has released precise measurements of elastic proton-proton scattering which has become an important guide in the search for selecting phenomenological models and theoretical approaches to understand, in a deeper level, the theory of strong interactions. In this thesis, through the formulation of two models compatible with analyticity and unitarity constraints, we study some aspects concerning the Physics behind hadronic interactions. In particular, we investigate the proton-proton and the antiproton-proton elastic scattering at high energies using a Regge theory-based model, where the increase of the total cross section is attributed to the exchange of a colorless state having the quantum numbers of the vacuum, and using a model based on the Quantum-Chromodynamics-improved parton model, where the increase of the total cross section is in turn associated with semihard scatterings of partons in the hadrons.

   hep-ph1 citation
2. 02*

   Hadron and Nuclear Physics on the Light Front

   Stanley J. Brodsky🇺🇸 · Alexandre Deur🇺🇸

   The QCD light-front (LF) Hamiltonian equation H_{LF}|\Psi> = M^2 |\Psi> derived from quantization at fixed LF time \tau = t+z/c provides a causal, frame-independent, method for computing hadron spectroscopy as well as dynamical observables such as structure functions, transverse momentum distributions, and distribution amplitudes. The LF formalism also leads to novel nuclear phenomena, such as "hidden color", "color transparency", "nuclear-bound quarkonium" and the shadowing and antishadowing of nuclear structure functions. For example, there are five distinct color-singlet Fock state representations of the six color-triplet quarks of the deuteron. The hidden color Fock states become manifest when the deuteron is probed when it has small transverse size, as in measurements of the deuteron form factor at large momentum transfer. The QCD Lagrangian with zero quark mass has no explicit mass scale. However, as shown by de Alfaro, Fubini, and Furlan (dAFF), a mass scale can appear in the equations of motion without affecting the conformal invariance of the Action. When one applies the dAFF procedure to the QCD LF Hamiltonian, it leads to a color confining potential \kappa^4 \zeta^2 for mesons, where \zeta^2 is the LF radial variable conjugate to the qbar-q invariant mass squared. The same result, including spin terms, is obtained using LF holography (AdS/QCD) -- the duality between LF dynamics and AdS_5 -- if one modifies the AdS_5 Action by the dilaton exp{+\kappa^2 z^2} in the fifth dimension z. If this procedure is generalized using superconformal algebra, the resulting LF eigensolutions provide unified Regge spectroscopy of mesons, baryons, and tetraquarks, including remarkable supersymmetric relations between the masses of mesons, baryons and tetraquarks with a universal Regge slope...

   hep-phhep-thnucl-thJPS Conf.Proc.(2020)·1 citation
3. 03*

   Centrality dependence of Electrical and Hall conductivity at RHIC and LHC energies for a Conformal System

   Bhaswar Chatterjee🇮🇳 · Rutuparna Rath🇮🇳 · Golam Sarwar🇮🇳 · Raghunath Sahoo

   In this work, we study electrical conductivity and Hall conductivity in the presence of electromagnetic field using Relativistic Boltzmann Transport Equation with Relaxation Time Approximation. We evaluate these transport coefficients for a strongly interacting system consisting of nearly massless particles which is similar to Quark-Gluon Plasma and is likely to be formed in heavy-ion collision experiments. We explicitly include the effects of magnetic field in the calculation of relaxation time. The values of magnetic field are obtained for all the centrality classes of Au+Au collisions at $\sqrt{s_{\mathrm{NN}}}=$ 200 GeV and Pb+Pb collisions at $\sqrt{s_{\mathrm{NN}}}=$ 2.76 TeV. We consider the three lightest quark flavors and their corresponding antiparticles in this study. We estimate the temperature dependence of the electrical conductivity and Hall conductivity for different strengths of magnetic field. We observe a significant dependence of temperature on electrical and Hall conductivity in the presence of magnetic field.

   hep-phnucl-exnucl-thEPJA(2021)·11 citations
4. 04*

   Modeling of Charged-Neutral Kaon Fluctuations as a Signature of DCC Production in A--A Collisions

   Ranjit Nayak🇮🇳 · Sadhana Dash🇮🇳 · Basanata Nandi🇮🇳 · Claude Pruneau🇺🇸

   Anomalous event-by-event fluctuations of the relative yields of neutral (K${}_s^0$) and charged kaon (K${}^{\pm }$) have been predicted to yield a signature for the formation of Disoriented Chiral Condensate (DCC) in relativistic heavy-ion collisions. In this work, we model the production and decay of DCCs in the context of heavy-ion collisions at the Large Hadron Collider, and estimate the sensitivity of large acceptance detectors, such as the ALICE detector, towards the identification of such anomalous decays. Our study is based on the robust statistical observable, ${\nu }_{\mathrm{dyn}}$, known for its sensitivity to dynamical fluctuations. We first present simulations without DCCs, based on the HIJING and AMPT models, in order to establish an approximate reference for the magnitude of ${\nu }_{\mathrm{dyn}}({\mathrm{K}}^{\pm },{\mathrm{K}}_s^0)$ and its centrality evolution in Pb--Pb collisions at the TeV energy scale. We next introduce simple phenomenological models of K${}_s^0$ vs. K${}^{\pm }$ event-by-event yield fluctuations, which we use to study the feasibility and sensitivity of detection of the production of DCCs in heavy-ion collisions. Although the precision of models such as HIJING and AMPT limit their use as absolute references and thus render anomalous fluctuations difficult to define precisely, our studies demonstrate that the magnitude of ${\nu }_{\mathrm{dyn}}({\mathrm{K}}^{\pm },{\mathrm{K}}_s^0)$ is in fact very sensitive to the presence of small admixture of DCCs in normal non-DCC events. Consequently, while large values of ${\nu }_{\mathrm{dyn}}({\mathrm{K}}^{\pm },{\mathrm{K}}_s^0)$ may not be sufficient to identify the existence of DCCs, nonetheless they constitute a first and necessary condition to signal their possible production in heavy-ion collisions.

   hep-phnucl-thPRC(2020)·11 citations
5. 05*

   Nucleon resonances in $\gamma p\to \omega p$ reaction

   N.C. Wei🇨🇳 · F. Huang🇨🇳 · K. Nakayama🇺🇸 · D. M. Li🇨🇳

   The most recent high-precision data on spin observables $\Sigma$, $T$, $P^{\prime }$, $E$, $F$ and $H$ reported by the CLAS Collaboration together with the previous data on differential cross sections and spin-density-matrix elements reported by the CLAS, A2, GRAAL, SAPHIR and CBELSA/TAPS Collaborations for the reaction $\gamma p\to \omega p$ are analyzed within an effective Lagrangian approach. The reaction amplitude is constructed by considering the $t$-channel $\pi$ and $\eta$ exchanges, the $s$-channel nucleon and nucleon resonances exchanges, the $u$-channel nucleon exchange and the generalized contact current. The latter accounts effectively for the interaction current and ensures that the full photoproduction amplitude is gauge invariant. It is shown that all the available CLAS data can be satisfactorily described by considering the $N(1520)3/2^{-}$, $N(1700)3/2^{-}$, $N(1720)3/2^{+}$, $N(1860)5/2^{+}$, $N(1875)3/2^{-}$, $N(1895)1/2^{-}$ and $N(2060)5/2^{-}$ resonances in the $s$-channel. The parameters of these resonances are extracted and compared with those quoted by PDG.

   hep-phnucl-thPRD(2019)·23 citations
6. 06*

   Pion off-shell electromagnetic form factors: data extraction and model analysis

   Ho-Meoyng Choi🇰🇷 · T. Frederico🇧🇷 · Chueng-Ryong Ji🇺🇸 · J. P. B. C. de Melo🇧🇷

   We investigate the pion electromagnetic half off-shell form factors, which parametrize the matrix element of the charged pion electromagnetic current with one leg off-mass-shell and the other leg on-mass-shell, using an exactly solvable manifestly covariant model of a $(3+1)$ dimensional fermion field theory. The model provides a 3D imaging of the two off-shell pion form factors $F_1$ and $F_2$ as a function of $(Q^2,t)$, which are related to each other satisfying the Ward-Takahashi identity. The normalization of the renormalized charge form factor $F_1$ is fixed by $F_1(Q^2=0,t=m_{\pi }^2)=1$ while the other form factor $F_2$ vanishes, i.e. $F_2(Q^2,t=m_{\pi }^2)=0$ for any value of $Q^2$ due to the time-reversal invariance of the strong interaction. We define the new form factor $g(Q^2,t)=F_2(Q^2,t)/(t-m_{\pi }^2)$ and find that $g(Q^2,t)$ can be measurable in the on-mass-shell limit. In particular, $g(Q^2=0,t=m_{\pi }^2)$ is related with the pion charge radius. We also compare our form factors with the data extracted from the pion electroproduction reaction for both the off-shell region ($t<0$) and the on-shell limit ($t\to m_{\pi }^2$).

   hep-phnucl-thPRD(2019)·14 citations
7. 07*

   Little hierarchies solve the little fine-tuning problem: a case study in supersymmetry with heavy guinos

   Thomas Deppisch🇩🇪 · Ulrich Nierste🇩🇪

   Radiative corrections with new heavy particles coupling to Higgs doublets destabilize the electroweak scale and require an ad-hoc counterterm cancelling the large loop contribution. If the mass scale m1 of these new particles in in the TeV range, this feature constitutes the "little fine-tuning problem". We consider the case that the new-physics spectrum has a little hierarchy with two particle mass scales m1, m2 and m2 = O(10 m1) and no tree-level couplings of the heavier particles to Higgs doublets. As a concrete example we study the (next-to-)minimal supersymmetric standard model ((N)MSSM) for the case that the gluino mass M3 is significantly larger than the stop mass parameters m_{L,R} and show that the usual one-loop fine-tuning analysis breaks down. If m_{L,R} is defined in the dimensional-reduction (DR-bar) or any other fundamental scheme, corrections enhanced by powers of M3^2/m_{L,R}^2 occur in all higher loop orders. After resumming these terms we find the fine-tuning measure substantially improved compared to the usual analyses with M3 <~ m_{L,R}. In our hierarchical scenario the stop self-energies grow like M3^2, so that the stop masses m_{L,R}^{OS} in the on-shell (OS) scheme are naturally much larger than their DR-bar counterparts m_{L,R}^{DR-bar}. This feature permits a novel solution to the little fine-tuning problem: DR-bar stop masses are close to the electroweak scale, but radiative corrections involving the heavy gluino push the OS masses, which are probed in collider searches, above their experimental lower limits. As a byproduct, we clarify which renormalization scheme must be used for squark masses in loop corrections to low-energy quantities such as the B-B-bar mixing amplitude.

   hep-ph3 citations
8. 08*

   Excited heavy quarkonium production in Higgs boson decays

   Qi-Li Liao🇨🇳 · Jun Jiang🇨🇳

   The rare decay channels of Higgs boson to heavy quarkonium offer vital opportunities to explore the coupling of Higgs to heavy quarks. We study the semi-exclusive decay channels of Higgs boson to heavy quarkonia, i.e., $H^0\to |(Q\overline{Q^{\prime }})[n]⟩+\bar{Q}{Q}^{\prime }$ ($Q^{(\prime )}=c\text{or}b$ quark) within the NRQCD framework. In addition to the lower-level Fock states $|(Q\overline{Q^{\prime }})[1S]⟩$ continent, contributions of high excited states $|(Q\overline{Q^{\prime }})[2S]⟩$, $|(Q\overline{Q^{\prime }})[3S]⟩$, $|(Q\overline{Q^{\prime }})[4S]⟩$, $|(Q\overline{Q^{\prime }})[1P]⟩$, $|(Q\overline{Q^{\prime }})[2P]⟩$, $|(Q\overline{Q^{\prime }})[3P]⟩$ and $|(Q\overline{Q^{\prime }})[4P]⟩$ are also studied. According to our study, the contributions of high excited Fock states should be considered seriously. Differential distributions of total decay width with respect to invariant-mass and angles, as well as uncertainties caused by non-perturbative hadronic non-perturbative matrix elements are discussed. If all excited heavy quarkonium states decay to the ground spin-singlet state through electromagnetic or hadronic interactions, we obtain the decay widths for $|(Q\overline{Q^{\prime }})⟩$ quarkonium production through $H^0$ semi-exclusive decays: $25.10_{-51.6\%}^{+11.6\%}$ keV for $|(b\bar{c})[n]⟩$ meson, $3.23_{-62.2\%}^{+0\%}$ keV for $|(c\bar{c})[n]⟩$ and $2.36_{-57.1\%}^{+0\%}$ keV for $|(b\bar{b})[n]⟩$, where uncertainties are caused by adopting different non-perturbative potential models. At future high energy LHC ($\sqrt{s}=27$ TeV), numerical results show that sizable amounts of events for those high excited states can be produced, which implies that one could also consider exploring the coupling properties of Higgs to heavy quarks in these high excited states channels, especially for the charmonium and bottomonium.

   hep-phPRD(2019)·14 citations
9. 09*

   Structure of proton based on the classical string model

   Z. G. Tan🇨🇳 · Y. F. Mo🇨🇳 · L. P. Sun🇨🇳

   In this paper, we propose several proton structure imagination scenarios based on classical string model. The radius and mass properties of protons in relativistic and non-relativistic cases are discussed, Contrary to asymptotic freedom, we find that the interaction between quarks in protons is inversely proportional to distance.

   hep-ph0 citations
10. 10*

    On the stability of two-flavor and three-flavor quark stars

    Qianyi Wang🇨🇳 · Tong Zhao🇨🇳 · Hongshi Zong🇨🇳

    Following our recenty proposed self-consistent mean-field approximation approach, we have done some researches on the chiral phase transition of strong interaction matter within the framework of Nambu-Jona-Lasinio (NJL) model. The chiral susceptibility and equation of state (EOS) are computed in this work for both two-flavor and three-flavor quark matter for contrast. The Pauli-Villars scheme, which can preserve gauge invariance, is used in this paper. Moreover, whether the three-flavor quark matter is more stable than the two-flavor quark matter or not in quark stars is discussed in this work. In our model, when the bag constant are the same, the two-flavor quark matter has a higher pressure than the three-flavor quark matter, which is different from what Witten proposed in his pioneering work.

    hep-phnucl-th10 citations
11. 11*

    Lorentz Breaking and SU(2)_L x U(1)_Y Gauge Invariance for Neutrino Decays

    U. D. Jentschura🇺🇸 · I. Nandori🇭🇺 · G. Somogyi🇭🇺

    Conceivable Lorentz-violating effects in the neutrino sector remain a research area of great general interest, as they touch upon the very foundations on which the Standard Model and our general understanding of fundamental interactions is laid. Here, we investigate the relation of Lorentz violation in the neutrino sector in light of the fact that neutrinos and corresponding left-handed charged leptons form SU(2)_L doublets under the electroweak gauge group. Lorentz-violating effects thus cannot be fully separated from questions related to gauge invariance. The model dependence of the effective interaction Lagrangians used in various recent investigations is investigated, with a special emphasis on neutrino splitting, otherwise known as neutrino-pair Cerenkov radiation, NPCR, and vacuum pair emission (electron-positron-pair Cerenkov radiation, LPCR). We investigate two scenarios in which Lorentz violating effects do not necessarily also break electroweak gauge invarianceThe first of these involves a restricted set of gauge transformation, a subgroup of SU(2)_L x U(1)_Y, while in the second, differential Lorentz violation is exclusively introduced by the mixing of the neutrino flavor and mass eigenstates. Our study culminates in a model which fully preserves SU(2)_L x U(1)_Y gauge invariance, involves flavor-dependent Lorentz-breaking parameters, and still allows for NPCR and LPCR decays to proceed.

    hep-phhep-thIJMPE(2019)·6 citations
12. 12*

    Probing of violation of Lorentz invariance by ultracold neutrons in the Standard Model Extension

    A. N. Ivanov🇦🇹 · M. Wellenzohn🇦🇹 · H. Abele🇦🇹

    We analyze a dynamics of ultracold neutrons (UCNs) caused by interactions violating Lorentz invariance within the Standard Model Extension (SME) (Colladay and Kostelecky, Phys. Rev. D55, 6760 (1997) and Kostelecky, Phys. Rev. D69, 105009 (2004)). We use the effective non-relativistic potential for interactions violating Lorentz invariance derived by Kostelecky and Lane (J. Math. Phys. 40, 6245 (1999)) and calculate contributions of these interactions to the transition frequencies of transitions between quantum gravitational states of UCNs bouncing in the gravitational field of the Earth. Using the experimental sensitivity of qBounce experiments we make some estimates of upper bounds of parameters of Lorentz invariance violation in the neutron sector of the SME which can serve as a theoretical basis for an experimental analysis. We show that an experimental analysis of transition frequencies of transitions between quantum gravitational states of unpolarized and polarized UCNs should allow to place some new constraints in comparison to the results adduced by Kostelecky and Russell in Rev. Mod. Phys. 83, 11 (2011); edition 2019, arXiv: 0801.0287v12 [hep-ph].

    hep-phgr-qcnucl-exPLB(2019)·24 citations
13. 13*

    Triple (and quadruple) soft-gluon radiation in QCD hard scattering

    Stefano Catani🇮🇹 · Dimitri Colferai🇮🇹 · Alessandro Torrini🇮🇹

    We consider the radiation of three soft gluons in a generic process for multiparton hard scattering in QCD. In the soft limit the corresponding scattering amplitude has a singular behaviour that is factorized and controlled by a colorful soft current. We compute the tree-level current for triple soft-gluon emission from both massless and massive hard partons. The three-gluon current is expressed in terms of maximally non-abelian irreducible correlations. We compute the soft behaviour of squared amplitudes and the colour correlations produced by the squared current. The radiation of one and two soft gluons leads to colour dipole correlations. Triple soft-gluon radiation produces in addition colour quadrupole correlations between the hard partons. We examine the soft and collinear singularities of the squared current in various energy ordered and angular ordered regions. We discuss some features of soft radiation to all-loop orders for processes with two and three hard partons. Considering triple soft-gluon radiation from three hard partons, colour quadrupole interactions break the Casimir scaling symmetry between quarks and gluons. We also present some results on the radiation of four soft gluons from two hard partons, and we discuss the colour monster contribution and its relation with the violation (and generalization) of Casimir scaling. We also compute the first correction of $\mathcal{O}(1/N_c^2)$ to the eikonal formula for multiple soft-gluon radiation with strong energy ordering from two hard gluons.

    hep-phJHEP(2020)·60 citations
14. 14*

    Extending parton branching TMDs to small $x$

    Sara Taheri Monfared🇩🇪 · Francesco Hautmann🇧🇪 · Hannes Jung🇩🇪 · Melanie Schmitz🇩🇪

    We explore the possibility to include small-$x$ dynamics effects in the parton branching (PB) approach to transverse momentum dependent (TMD) parton distribution functions. To this end, we first revisit the PB method at leading order, presenting a new fit to inclusive-DIS precision data, and performing a numerical study of the dynamic soft-gluon resolution scale. Next we investigate the effects of modified CCFM kernels, including both Sudakov and non-Sudakov form factors.

    hep-phPoS(2019)·11 citations
15. 15*

    Discussing 125 GeV and 95 GeV excess in Light Radion Model

    Divya Sachdeva🇮🇳 · Soumya Sadhukhan🇮🇳

    Even if the LHC observations are consistent with the Standard model (SM), current LHC results are not precise enough to rule out the presence of new physics. Taking a contrarian view of the SM Higgs fandom, we look out for a more suitable candidate for the 125 GeV boson observed at the LHC. At the same time, a recent result from CMS hints towards an excess near 95 GeV in the diphoton ($\gamma \gamma$) channel. Given these aspects, we revisit the Higgs-radion mixing model to explore the viability of the radion mixed Higgs to be the 125 GeV boson along with the presence of a light radion (to be precise Higgs mixed radion) that can show up in future experiments in the $\gamma \gamma$ channel. We find that the mixed radion-Higgs scenario gives a better fit than the SM, with the radion mixed Higgs as a more suitable 125 GeV scalar candidate. It also gives rise to a diphoton excess from the light radion, consistent with the LHC observations.

    hep-phPRD(2020)·22 citations
16. 16*

    Full two-loop QCD corrections to the Higgs mass in the MSSM with heavy superpartners

    Emanuele Bagnaschi🇨🇭 · Giuseppe Degrassi🇮🇹 · Sebastian Paßehr🇫🇷 · Pietro Slavich🇫🇷

    We improve the determination of the Higgs-boson mass in the MSSM with heavy superpartners, by computing the two-loop threshold corrections to the quartic Higgs coupling that involve both the strong and the electroweak gauge couplings. Combined with earlier results, this completes the calculation of the two-loop QCD corrections to the quartic coupling at the SUSY scale. We also compare different computations of the relation between the quartic coupling and the pole mass of the Higgs boson at the EW scale. We find that the numerical impact of the new corrections on the prediction for the Higgs mass is modest, but comparable to the accuracy of the Higgs-mass measurement at the LHC.

    hep-phEPJC(2019)·30 citations
17. 17*

    The QCD Axion and Unification

    Pavel Fileviez Perez🇺🇸 · Clara Murgui🇪🇸 · Alexis D. Plascencia🇺🇸

    The QCD axion is one of the most appealing candidates for the dark matter in the Universe. In this article, we discuss the possibility to predict the axion mass in the context of a simple renormalizable grand unified theory where the Peccei-Quinn scale is determined by the unification scale. In this framework, the axion mass is predicted to be in the range $m_a\simeq (3-13)\times 10^{-9}\mathrm{eV}$. We study the axion phenomenology and find that the ABRACADABRA and CASPEr-Electric experiments will be able to fully probe this mass window.

    hep-phhep-exhep-thJHEP(2019)·34 citations
18. 18*

    The soft drop groomed jet radius at NLL

    Zhong-Bo Kang🇺🇸 · Kyle Lee🇺🇸 · Xiaohui Liu🇨🇳 · Duff Neill🇺🇸 · Felix Ringer🇺🇸

    We present results for the soft drop groomed jet radius $R_g$ at next-to-leading logarithmic accuracy. The radius of a groomed jet which corresponds to the angle between the two branches passing the soft drop criterion is one of the characteristic observables relevant for the precise understanding of groomed jet substructure. We establish a factorization formalism that allows for the resummation of all relevant large logarithms, which is based on demonstrating the all order equivalence to a jet veto in the region between the boundaries of the groomed and ungroomed jet. Non-global logarithms including clustering effects due to the Cambridge/Aachen algorithm are resummed to all orders using a suitable Monte Carlo algorithm. We perform numerical calculations and find a very good agreement with Pythia 8 simulations. We provide theoretical predictions for the LHC and RHIC.

    hep-phhep-exnucl-exnucl-thJHEP(2020)·57 citations
19. 19*

    Novel Signals from Neutron Star Mergers at 511 keV

    Volodymyr Takhistov🇺🇸

    Synergetic observations of multi-band coincidence signals from merging neutron stars have definitively marked the significance of multi-messenger astronomy. We present a new generic signature of neutron star mergers, positron emission and the associated 511 keV radiation, produced from ejected neutron-rich radioactive merger material. Accounting for historical neutron star mergers within the Milky Way allows to readily explain the origin of the long-observed 511 keV emission line from the Galactic Center. Further, we draw a direct link between heavy element production ($r$-process nucleosynthesis) and 511 keV emission, which signifies the surprising recent observations of Reticulum II ultra-faint dwarf spheroidal galaxy as a smoking gun of our proposal. This novel tracer of neutron star mergers provides a distinct handle for exploring binary merger history.

    ↳ astro-ph.HEhep-phPoS(2020)·3 citations
20. 20*

    Backward nucleon production by heavy baryonic resonances in proton-nucleus collisions

    Oleksandra Panova🇺🇦 · Anton Motornenko🇩🇪 · Mark I. Gorenstein🇺🇦 · Jan Steinheimer🇩🇪 · Horst Stoecker🇩🇪

    The production of backward nucleons, $N(180^{\circ })$, at $180^{\circ }$ in the nuclear target rest frame in proton-nucleus ($\mathrm{p}+A$) collisions is studied. The backward nucleons appearing outside of the kinematically allowed range of proton-nucleon ($\mathrm{p}+N$) reactions are shown to be due to secondary reactions of heavy baryonic resonances produced inside the nucleus. Baryonic resonances $R$ created in primary $\mathrm{p}+N$ reactions can change their masses and momenta due to successive collisions $R+N\to R+N$ with other nuclear nucleons. Two distinct mechanisms and kinematic restrictions are studied: the reaction $R+N\to N(180^{\circ })+N$ and the resonance decay $R\to N(180^{\circ })+\pi$. Simulations of $\mathrm{p}+A$ collisions using the Ultra-relativistic Quantum Molecular Dynamics model support these mechanisms and are consistent with available data on proton backward production.

    ↳ nucl-thhep-phPRC(2019)·5 citations
21. 21*

    Cosmological constraints in extended parameter space from the Planck 2018 Legacy release

    Eleonora Di Valentino🇬🇧 · Alessandro Melchiorri🇮🇹 · Joseph Silk🇫🇷

    We present new constraints on extended cosmological scenarios using the recent data from the Planck 2018 Legacy release. In addition to the six parameters of the standard LCDM model, we also simultaneously vary the dark energy equation of state, the neutrino mass, the neutrino effective number, the running of the spectral index and the lensing amplitude $A_L$. We confirm that a resolution of the Hubble tension is given by a dark energy equation of state with w<-1, ruling out quintessence models at high statistical significance. This solution is, however, not supported by BAO and Pantheon data. We find no evidence for evolving dark energy, i.e. $w_a\ne 0$. The neutrino effective number is always in agreement with the expectations of the standard model based on three active neutrinos. The running of the spectral index also is always consistent with zero. Despite the increase in the number of parameters, the $A_L$ lensing anomaly is still present at more than two standard deviations. The $A_L$ anomaly significantly affects the bounds on the neutrino mass that can be larger by a factor four with respect to those derived under standard $\Lambda$CDM. While the lensing data reduces the evidence for $A_L>1$, the inclusion of BAO and Pantheon increase its statistical significance.

    ↳ astro-ph.COgr-qchep-phJCAP(2020)·157 citations
22. 22*

    Grand Unified Theories in Renormalisable, Classically Scale Invariant Gravity

    Martin B Einhorn🇺🇸 · D R Timothy Jones🇺🇸

    We analyze $SO(N)$ and $SU(N)$ gauge theories with scalars in adjoint and fundamental representations, coupled to renormalisable, classically scale invariant gravity. In the specific case of $SO(12),$ we show that the quantum field theory can be can be asymptotically free in all couplings (hence ultra-violet complete). For a region of parameter space, Dimensional Transmutation occurs, with the adjoint vacuum expectation value breaking $SO(12)\to SU(6)\otimes U(1)$ and producing a Low Energy Effective Theory having Einstein-Hilbert gravity. We verify that certain minima are locally stable and lie within the catchment basin of the ultraviolet fixed points.

    ↳ hep-thgr-qchep-phJHEP(2019)·6 citations
23. 23*

    New Venues in Formation and Detection for Primordial Black Hole Dark Matter

    Volodymyr Takhistov🇺🇸

    Primordial black holes (PBHs) are not as exotic as once thought and constitute a compelling non-particle dark matter (DM) candidate. We present a novel general PBH formation mechanism from scalar field fragmentation, which does not suffer from the inflaton potential fine-tuning that plagues many of the standard PBH formation models. We discuss how interactions of compact stars with very small sub-lunar/asteroid-size PBHs, which reside in the open window of parameter space where PBHs can constitute all of DM, allow for a slew of new astrophysical signatures that could shed light on PBH DM and are particularly interesting in the era of multi-messenger astronomy.

    ↳ astro-ph.COastro-ph.HEhep-phPoS(2020)·2 citations
24. 24*

    Black Hole Binary Dynamics from the Double Copy and Effective Theory

    Zvi Bern🇺🇸 · Clifford Cheung🇺🇸 · Radu Roiban🇺🇸 · Chia-Hsien Shen🇺🇸 · Mikhail P. Solon🇺🇸 · Mao Zeng🇨🇭

    We describe a systematic framework for computing the conservative potential of a compact binary system using modern tools from scattering amplitudes and effective field theory. Our approach combines methods for integration and matching adapted from effective field theory, generalized unitarity, and the double-copy construction, which relates gravity integrands to simpler gauge-theory expressions. With these methods we derive the third post-Minkowskian correction to the conservative two-body Hamiltonian for spinless black holes. We describe in some detail various checks of our integration methods and the resulting Hamiltonian.

    ↳ hep-thgr-qchep-phJHEP(2019)·542 citations
25. 25*

    Jet charge in high energy nuclear collisions

    Shi-Yong Chen🇨🇳 · Ben-Wei Zhang🇨🇳 · En-Ke Wang🇨🇳

    Averaged jet charge characterizes the electric charge for the initiating parton, and provides a powerfull tool to distinguish quark jets from gluon jets. In this paper, we give the first prediction for the medium modification of averaged jet charge in heavy-ion collision at the LHC, where jet productions in p+p collisions are simulated by PYTHIA6, and parton energy loss in QGP are calculated with two Monte Carlo models of jet quenching: PYQUEN and JEWEL. We found that the distribution of averaged jet charge is significantly suppressed by initial state isospin effects due to the participants of neutrons with zero electric charge during nuclear collisions. Considerable enhancement of averaged jet charge in central Pb+Pb collisions relative to peripheral collisions is observed, since jet quenching effect is more pronounced in central collisions. Distinct feature of averaged jet charge between quark and gluon jets, together with the sensitivity of medium modifications on jet charge to flavor dependence of parton energy loss, could be very useful to discriminate the energy loss pattern between quark and gluon jets in heavy-ion collisions.

    ↳ nucl-thhep-phCPC(2020)·32 citations
26. 26*

    Electroweak Current Operators in Chiral Effective Field Theory

    Hermann Krebs🇩🇪

    In this proceeding I briefly review current status of the construction of nuclear electro-weak currents within chiral effective field theory. I show that gauge and chiral symmetry requirements lead to the well-known continuity equations for the current and charge operators which, however, get modified at higher orders. Regularization of the current will be also discussed. I demonstrate that implementation of a cutoff regulator in a naive way leads to violation of chiral symmetry. To respect the underlying symmetries I propose to use higher derivative regularization in the nuclear forces and currents.

    ↳ nucl-thhep-phPoS(2019)·14 citations
27. 27*

    Hunting for T-violation and Majoranality of Neutrinos in Muon Decays

    Takeshi Fukuyama🇯🇵 · Sohtaro Kanda🇯🇵 · Daisuke Nomura🇯🇵 · Koichiro Shimomura🇯🇵

    We propose a new experiment to search for a time-reversal (T) symmetry breaking process in muon decay and the Majoranality of the neutrinos. In the presence of V+A interactions, the Majoranality appears as a T-violating term in the muon decay width as shown by Doi et al, while in the Standard Model such a T-violating term is negligibly small. The presences of V+A interactions and the corresponding heavy right-handed Majorana neutrinos give us an important clue to solve two major issues in particle physics, the deficit of baryon asymmetry in the universe and the Majoranality of neutrinos. In the experiment, the polarization of positrons from muon decays is measured using a polarimeter consisting of a magnetized foil and a segmented calorimeter. According to our result of numerical calculation, a factor of ten improvement in sensitivity to the T-violating process is expected by a year of measurement at J-PARC Materials and Life Science Experimental Facility, compared to the most recent precursor experiment.

    ↳ hep-exhep-ph3 citations
28. 28*

    Noncovariance at low accelerations as a route to MOND

    Mordehai Milgrom🇮🇱

    MOND has limelighted the fact that Newtonian dynamics (ND) and general relativity (GR) have not been verified at accelerations below MOND's $a_0$. In particular, we do not know that all the principles underlying ND or GR apply below $a_0$. I discuss possible breakdown of general covariance (GC) in this limit. This resonates well with MOND, which hinges on accelerations. Relaxing GC affords more freedom in constructing MOND theories. I exemplify this with a simplified theory whose gravitational Lagrangian is ${\mathcal{L}}_M\propto {\ell }_M^{-2}\mathcal{F}({\ell }_M^2\mathcal{R})$, where $\mathcal{R}=g^{\mu \nu }({\Gamma }_{\mu \nu }^{\gamma }{\Gamma }_{\lambda \gamma }^{\lambda }-{\Gamma }_{\mu \lambda }^{\gamma }{\Gamma }_{\nu \gamma }^{\lambda })/2$. ${\Gamma }_{\mu \nu }^{\gamma }$ is the Levi-Civita connection of a metric, $g_{\mu \nu }$, and ${\ell }_M=c^2/a_0$ is the MOND length. Requiring $\mathcal{F}(z)\to z+\zeta$, for $z\gg 1$ gives GR with a cosmological constant $\zeta c^{-4}{a}_0^2$ for high accelerations. In the MOND limit ${\mathcal{F}}^{\prime }(z\ll 1)\propto z^{1/2}$. In the nonrelativistic limit the metric is of the form $g_{\mu \nu }\approx {\eta }_{\mu \nu }-2\varphi {\delta }_{\mu \nu }$, as in GR, but the potential $\varphi$ solves a MOND, nonlinear Poisson analog. This form of $g_{\mu \nu }$ also produces gravitational lensing as in GR only with the MOND potential. I show that this theory is a fixed-gauge expression of BIMOND, with the auxiliary metric constrained to be flat. The latter theory is thus a covariantized version of the former a-la Stückelberg. This theory is also a special case of so-called $f(\mathcal{Q})$ theories -- aquadratic generalizations of `symmetric, teleparallel GR', which are, in turn, also equivalent to constrained BIMOND-type theories. (Abridged.)

    ↳ gr-qcastro-ph.COastro-ph.GAhep-phPRD(2019)·45 citations
29. 29*

    Beam-beam effects on the luminosity measurement at LEP and the number of light neutrino species

    Georgios Voutsinas🇨🇭 · Emmanuel Perez🇨🇭 · Mogens Dam🇩🇰 · Patrick Janot🇨🇭

    In $e^{+}{e}^{-}$ collisions, electromagnetic effects caused by large charge density bunches modify the effective acceptance of the luminometer system of the experiments. These effects consequently bias the luminosity measurement from the rate of low-angle Bhabha interactions $e^{+}{e}^{-}\to e^{+}{e}^{-}$. Surprisingly enough, the magnitude of this bias is found to yield an underestimation of the integrated luminosity measured by the LEP experiments by about 0.1%, significantly larger than the reported experimental uncertainties. When accounted for, this effect modifies the number of light neutrino species determined at LEP from the measurement of the hadronic cross section at the Z peak.

    ↳ hep-exhep-phphysics.acc-phPLB(2020)·39 citations
30. 30*

    Transversely polarized Drell-Yan measurements at COMPASS

    Bakur Parsamyan🇨🇭

    The exploration of the transverse spin structure of the nucleon by measuring spin (in)dependent azimuthal asymmetries in semi-inclusive DIS (SIDIS) and in Drell-Yan processes is one of the main objectives of the COMPASS experiment at CERN (SPS, M2 beamline). During the first phase of the experiment (2002-2011) a series of SIDIS measurements were performed, using a longitudinally polarized muon beam impinging on transversely polarized ${}^6$LiD or NH${}_3$ targets. As a part of the COMPASS-II programme, in 2015 and 2018 the experiment performed Drell-Yan measurements with a ${\pi }^{-}$ beam interacting with a transversely polarized NH${}_3$. The measurement of the Sivers and other azimuthal asymmetries at the same hard scale in polarized SIDIS and Drell-Yan provides a unique possibility to test predicted in QCD (pseudo-)universal features of transverse momentum dependent parton distribution functions.

    ↳ hep-exhep-phPoS(2019)·6 citations
31. 31*

    Tunneling Without Bounce

    J.R. Espinosa🇪🇸

    The false vacua of some potentials do not decay via Euclidean bounces. This typically happens for tunneling actions with a flat direction (in field configuration space) that is lifted by a perturbation into a sloping valley, pushing the bounce off to infinity. Using three different approaches we find a consistent picture for such decays. In the Euclidean approach the bottom of the action valley consists of a family of pseudo-bounces (field configurations with some key good properties of bounces except extremizing the action). The pseudo-bounce result is validated by minimizing a WKB action in Minkowski space along appropriate paths in configuration space. Finally, the simplest approach uses the tunneling action method proposed recently with a simple modification of boundary conditions.

    ↳ hep-thhep-phPRD(2019)·35 citations
32. 32*

    Gravitational Lensing Signatures of Axion Dark Matter Minihalos in Highly Magnified Stars

    Liang Dai🇺🇸 · Jordi Miralda-Escudé🇺🇸

    Axions are a viable candidate for Cold Dark Matter (CDM) which should generically form minihalos of sub-planetary masses from white-noise isocurvature density fluctuations if the Peccei-Quinn phase transition occurs after inflation. Despite being denser than the larger halos formed out of adiabatic fluctuations from inflation, axion minihalos have surface densities much smaller than the critical value required for gravitational lensing to produce multiple images or high magnification, and hence are practically undetectable as lenses in isolation. However, their lensing effect can be enhanced when superposed near critical curves of other lenses. We propose a method to detect them through photometric monitoring of recently discovered caustic transiting stars behind cluster lenses, under extreme magnification factors $\mu \gtrsim 10^3$--$10^4$ as the lensed stars cross microlensing caustics induced by intracluster stars. For masses of the first gravitationally collapsed minihalos in the range $\sim 10^{-15}$--$10^{-8}{h}^{-1}{M}_{\odot }$, we show that axion minihalos in galaxy clusters should collectively produce subtle surface density fluctuations of amplitude $\sim 10^{-4}$--$10^{-3}$ on projected length scales of $\sim 10$--$10^4$AU, which imprint irregularities in the microlensing light curves of caustic transiting stars. We estimate that, inside a cluster halo and over the age of the Universe, most of these minihalos are likely to avoid dynamic disruption by encounters with stars or other minihalos.

    ↳ astro-ph.COhep-phAstron.J.(2020)·123 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.