Fri·Sep 14, 2018Friday·September 14, 2018

1. 01*

   Quark jets scattering from a gluon field: from saturation to high $p_t$

   Jamal Jalilian-Marian🇺🇸

   We continue our studies of possible generalization of the Color Glass Condensate (CGC) effective theory of high energy QCD to include the high $p_t$ (or equivalently large $x$) QCD dynamics as proposed in [JJM-elastic]. Here we consider scattering of a quark from both the small and large $x$ gluon degrees of freedom in a proton or nucleus target and derive the full scattering amplitude by including the interactions between the small and large $x$ gluons of the target. We thus generalize the standard eikonal approximation for parton scattering which can now be deflected by a large angle (and therefore have large $p_t$) and also lose a significant fraction of its longitudinal momentum (unlike the eikonal approximation). The corresponding production cross section can thus serve as the starting point toward derivation of a general evolution equation that would contain DGLAP evolution equation at large $Q^2$ and the JIMWLK evolution equation at small $x$. This amplitude can also be used to construct the quark Feynman propagator which is the first ingredient needed to generalize the Color Glass Condensate (CGC) effective theory of high energy QCD to include the high $p_t$ dynamics. We outline how it can be used to compute observables in the large $x$ (high $p_t$) kinematic region where the standard Color Glass Condensate formalism breaks down.

   hep-phPRD(2019)·61 citations
2. 02*

   Superstatistics and the effective QCD phase diagram

   Alejandro Ayala🇲🇽 · Martin Hentschinski🇲🇽 · Luis Alberto Hernandez🇲🇽 · Marcelo Loewe🇨🇱 · Renato Zamora🇨🇱

   We study the effect of a partially thermalized scenario for chiral symmetry restoration at finite temperature and quark chemical potential, and in particular for the position of the critical end point in an effective description of the QCD phase diagram. We show that these effects produce the critical end point to be displaced towards larger values of temperature and lower values of the quark chemical potential as compared to the case when the system can be regarded as completely thermalized. We conclude that these effects may be important for relativistic heavy ion collisions where the number of subsystems making the whole interaction volume can be linked to the finite number of participants in the reaction.

   hep-phnucl-thPRD(2018)·26 citations
3. 03*

   $P$-wave contributions to $B\to \psi \pi \pi$ decays in perturbative QCD approach

   Zhou Rui🇨🇳 · Ya Li🇨🇳 · Hsiang-nan Li🇹🇼

   We present the differential branching fractions for the $B\to \psi \pi \pi$ decays with the charmonia $\psi =J/\psi ,\psi (2S)$ in the invariant mass of the $P$-wave pion pairs in the perturbative QCD approach. The two-pion distribution amplitudes (DAs) corresponding to both longitudinal and transverse polarizations are constructed to capture important final state interactions in the processes. The time-like form factors, normalizing the two-pion DAs, contains contributions from the $\rho$ resonance and radial excitations fitted to the BaBar data. Given the hadronic parameters for the two-pion DAs associated with the longitudinal polarization which were determined in our previous study, and tuning those associated with the transverse polarization, we accommodate well the observed branching ratios and polarization fractions of the $B\to J/\psi \pi \pi$ decays. Our predictions for the $B\to \psi (2S)\pi \pi$ modes from the same set of parameters can be tested in future LHCb and BelleII experiments. We also investigate the sources of theoretical uncertainties in our calculation.

   hep-phhep-exPRD(2018)·29 citations
4. 04*

   Pseudoscalar decays to gauge bosons at the LHC and at a future 100 TeV collider

   Abdesslam Arhrib🇲🇦 · Rachid Benbrik🇲🇦 · Jaouad El Falaki🇲🇦 · Marco Sampaio🇵🇹 · Rui Santos🇵🇹

   We discuss the search for a CP-odd scalar decaying into gauge bosons in the framework of a CP-conserving two-Higgs doublet model (2HDM) and of a 2HDM extended with a vector-like quark (VLQ) at the Large Hadron Collider and at a future 100 TeV collider. The rate of decay of a pseudoscalar to $Z$-bosons could be important to ascertain the CP-nature of the scalars in the model. In the 2HDM $A\to ZZ$ will be extremely hard to detect even at a future 100 TeV $pp$ collider while in the 2HDM+VLQ this decay can be probed even during the present LHC run. We further discuss all decays of the pseudoscalar into gauge bosons at the LHC and at a future 100 TeV collider in the alignment limit where the lightest scalar is the 125 GeV Higgs with SM-like couplings to the fermions and gauge bosons.

   hep-phPRD(2019)·10 citations
5. 05*

   Freeze-in production of decaying dark matter in five steps

   Saniya Heeba🇩🇪 · Felix Kahlhoefer🇩🇪 · Patrick Stöcker🇩🇪

   We study the cosmological evolution and phenomenological properties of scalar bosons in the keV to MeV range that have a tiny mixing with the Standard Model Higgs boson. The mixing determines both the abundance of light scalars produced via the freeze-in mechanism and their lifetime. Intriguingly, the parameters required for such scalars to account for all of the dark matter in the present Universe generically predict lifetimes comparable to the sensitivity of present and future indirect detection experiments. In order to accurately determine the relic abundance of light scalars, we calculate freeze-in yields including effects from finite temperatures and quantum statistics and develop a new approach for solving the Boltzmann equation for number-changing processes in the dark sector. We find that light scalars can potentially explain the anomalous x-ray emission at 3.5 keV, while evading constraints from structure formation and predicting potentially observable self-interaction cross sections.

   hep-phastro-ph.COJCAP(2018)·76 citations
6. 06*

   Current status of Two-Higgs-Doublet models with a softly broken ${\mathbb{Z}}_2$ symmetry

   Otto Eberhardt🇪🇸

   One of the most popular extensions of the Standard Model is the Two-Higgs-Doublet model (2HDM), in which a second Higgs doublet is added to the conventional Standard Model particle content. 2HDM's with a softly broken ${\mathbb{Z}}_2$ symmetry avoid flavour-changing neutral Higgs currents at tree-level. They also comprise the Higgs sector of the Minimal Supersymmetric Standard Model. Current Higgs observables put strong constraints on these models. We present global fits to these data and combine them with information from theoretical bounds, electroweak precision observables and the most important flavour constraints, using the open-source package HEPfit. The resulting limits on the 2HDM parameters like mixing angles, the heavy Higgs masses as well as the allowed Higgs mass splittings will be discussed.

   hep-phhep-exPoS(2019)·6 citations
7. 07*

   Double longitudinal-spin asymmetries in $J/\psi$ production at RHIC

   Yu Feng🇨🇳 · Hong-Fei Zhang🇨🇳

   The double longitudinal-spin asymmetry, $A_{LL}$, of the $J/\psi$ production in polarized proton-proton collisions is presented in this paper at QCD next-to-leading order. It is found that the obtained values of $A_{LL}$ are in general consistent with the PHENIX measurements. Various sets of the long-distance matrix elements (LDMEs) are employed in our calculation to study the possible theoretical uncertainties. It is found that, for $p_t<5\text{gev}$, all these LDMEs lead to almost the same results, which are within the tolerance of the experimental data uncertainties.

   hep-phhep-exJHEP(2018)·5 citations
8. 08*

   Bubble wall velocities in the Standard Model and beyond

   Glauber C. Dorsch🇩🇪 · Stephan J. Huber🇬🇧 · Thomas Konstandin🇩🇪

   We present results for the bubble wall velocity and bubble wall thickness during a cosmological first-order phase transition in a condensed form. Our results are for minimal extensions of the Standard Model but in principle are applicable to a much broader class of settings. Our first assumption about the model is that only the electroweak Higgs is obtaining a vacuum expectation value during the phase transition. The second is that most of the friction is produced by electroweak gauge bosons and top quarks. Under these assumptions the bubble wall velocity and thickness can be deduced as a function of two equilibrium properties of the plasma: the strength of the phase transition and the pressure difference along the bubble wall.

   hep-phJCAP(2018)·103 citations
9. 09*

   Recent progress in PDF theory

   Marco Bonvini🇮🇹

   We discuss the recent results obtained in the context of PDF determination with the inclusion of logarithmic resummations and their phenomenological applications.

   hep-phhep-exPoS(2018)·0 citations
10. 10*

    Decay patterns of low-lying $N_{s\bar{s}}$ states to the strangeness channels

    Chun-Sheng An🇨🇳 · Ju-Jun Xie🇨🇳 · Gang Li🇨🇳

    Here we investigate the decay patterns of the low-lying hidden strangeness nucleon resonances ($\equiv N_{s\bar{s}}$) to the strangeness channels by employing the chiral Lagrangian approach, where the $N_{s\bar{s}}$ states are treated as compact pentaquark states. The $S$-wave decays of these states to the $PB$ (pseudoscalar meson and baryon) and $VB$ (vector meson and baryon) channels are studied. According to the obtained masses and decay properties, we find four states, namely, $N_{s\bar{s}}(1874)$ with quantum numbers $I(J^P)=1/2(1/2^{-})$, $N_{s\bar{s}}(1885)$ with $I(J^P)=1/2(3/2^{-})$, $N_{s\bar{s}}(2327)$ with $I(J^P)=1/2(1/2^{-})$, and $N_{s\bar{s}}(2252)$ with $I(J^P)=1/2(3/2^{-})$, may be associated to the well established nucleon resonances $N^{\ast }(1895)$, $N^{\ast }(1875)$, and the newly predicted $N^{\ast }(2355)$ and $N^{\ast }(2250)$ by CLAS collaboration, respectively. In addition, several other obtained hidden strangeness nucleon resonances may be expected to be dominant components of the predicted missing resonances in the literatures.

    hep-phPRC(2018)·8 citations
11. 11*

    Chiral anomaly and strange-nonstrange mixing

    Francesco Giacosa🇵🇱

    As a first step, a simple and pedagogical recall of the $\eta$-${\eta }^{\prime }$ system is presented, in which the role of the axial anomaly, related to the heterochiral nature of the multiplet of (pseudo)scalar states, is underlined. As a consequence, $\eta$ is close to the octet and ${\eta }^{\prime }$ to the singlet configuration. On the contrary, for vector and tensor states, which belong to homochiral multiplets, no anomalous contribution to masses and mixing is present. Then, the isoscalar physical states are to a very good approximation nonstrange and strange, respectively. Finally, for pseudotensor states, which are part of an heterochiral multiplet (just as pseudoscalar ones), a sizable anomalous term is expected: ${\eta }_2(1645)$ roughly corresponds to the octet and ${\eta }_2(1870)$ to the singlet.

    hep-phEPJ Web Conf.(2019)·1 citation
12. 12*

    Nonperturbative strange-quark sea from lattice QCD, light-front holography, and meson-baryon fluctuation models

    Raza Sabbir Sufian🇺🇸 · Tianbo Liu🇺🇸 · Guy F. de Téramond🇨🇷 · Hans Günter Dosch🇩🇪 · Stanley J. Brodsky🇺🇸 · Alexandre Deur🇺🇸 · Mohammad T. Islam🇺🇸 · Bo-Qiang Ma🇨🇳

    We demonstrate that a nonzero strangeness contribution to the spacelike electromagnetic form factor of the nucleon is evidence for a strange-antistrange asymmetry in the nucleon's light-front wave function, thus implying different nonperturbative contributions to the strange and antistrange quark distribution functions. A recent lattice QCD calculation of the nucleon strange quark form factor predicts that the strange quark distribution is more centralized in coordinate space than the antistrange quark distribution, and thus the strange quark distribution is more spread out in light-front momentum space. We show that the lattice prediction implies that the difference between the strange and antistrange parton distribution functions, $s(x)-\bar{s}(x)$, is negative at small-$x$ and positive at large-$x$. We also evaluate the strange quark form factor and $s(x)-\bar{s}(x)$ using a baryon-meson fluctuation model and a novel nonperturbative model based on light-front holographic QCD. This procedure leads to a Veneziano-like expression of the form factor, which depends exclusively on the twist of the hadron and the properties of the Regge trajectory of the vector meson which couples to the quark current in the hadron. The holographic structure of the model allows us to introduce unambiguously quark masses in the form factors and quark distributions preserving the hard scattering counting rule at large-$Q^2$ and the inclusive counting rule at large-$x$. Quark masses modify the Regge intercept which governs the small-$x$ behavior of quark distributions, therefore modifying their small-$x$ singular behavior. Both nonperturbative approaches provide descriptions of the strange-antistrange asymmetry and intrinsic strangeness in the nucleon consistent with the lattice QCD result.

    hep-phhep-exhep-latnucl-thPRD(2018)·44 citations
13. 13*

    Phenomenology of doublet-triplet fermionic dark matter in nonstandard cosmology and multicomponent dark sectors

    Amalia Betancur🇨🇴 · Óscar Zapata🇨🇴

    We consider the doublet-triplet fermionic model in the scheme of the custodial limit when the dark matter (DM) candidate is pure doublet and lies at the electroweak scale. This scheme, despite being an appealing and promising DM model, is severely constrained by the interplay between the DM relic density constraint and the LHC measurement of the Higgs diphoton decay rate. In this work, the DM relic density is considered to arise from either a nonstandard cosmology scenario or as a part of a larger sector encompassing other DM particles, this in order to saturate the observed relic abundance. For these scenarios we investigate the impact of the new sector in different collider observables, and study constraints coming from direct detection and indirect detection of gamma-rays both in the diffuse and linelike spectrum. As a result, we find that in the nonstandard cosmology scenario most experiments impose, up to a certain point, restrictions, though large portions of the parameter space are still viable. For the multicomponent case, only direct detection imposes constraints.

    hep-phPRD(2018)·26 citations
14. 14*

    MICROSCOPE limits on the strength of a new force, with comparisons to gravity and electromagnetism

    Pierre Fayet🇫🇷

    Extremely weak new forces could lead to apparent violations of the Equivalence Principle. The MICROSCOPE experiment implies that the relative strength of a new long-range force, compared with gravity, is constrained to $|{\bar{\alpha }}_g|<3.210^{-11},2.310^{-13},2.210^{-13},6.710^{-13}$ and $1.510^{-12}$ at $2\sigma$, for a coupling to $B,L,B-L,B+L$ or $3B+L$; or, for a coupling to isospin, $|{\alpha }_g|<8.410^{-12}$. This is a gain in sensitivity $\simeq 3$ for a coupling to $B$, to $\approx$ 15 in the other cases, including $B-L$ as suggested by grand unification. This requires paying attention to the definition of ${\bar{\alpha }}_g$. A force coupled to $L$ (or $B-L$) would act effectively on protons (or neutrons) only, its relative intensity being reduced from ${\alpha }_g$ to about ${\bar{\alpha }}_g={\alpha }_g/4$ for an average nucleon. It is thus convenient to view such forces as acting on $\bar{Q}=B,2L,2(B-L),2(B+L)/3$ or $2(3B+L)/7$, leading to ${\bar{\alpha }}_g={\alpha }_g\times (1,1/4,1/4,9/4$ or $49/4$). The sensitivity for a coupling to $L$ or $B-L$ is better than for $B$ by two orders of magnitude (as $\Delta (2L/A_r)\simeq 144\Delta (B/A_r)$ for Ti-Pt); and about 3 or 7 times better than for $B+L$ or $3B+L$. A coupling to $({ϵ}_{B}B+{ϵ}_{Q_{el}}{Q}_{el})e$ should verify $|{ϵ}_B|<510^{-24}$; similarly $|{ϵ}_L|$ or $|{ϵ}_{B-L}|<.910^{-24}$, $|{ϵ}_{B+L}|<.510^{-24},|{ϵ}_{3B+L}|<.3210^{-24}$ and $|{ϵ}_{B-2L}|<2.610^{-24}$, implying a new interaction weaker than electromagnetism by more than $10^{46}$ to $10^{48}$. The resulting hierarchy between couplings, typically by $>10^{24}$, may be related within supersymmetry with a large hierarchy in energy scales by $>10^{12}$. This points to a $\sqrt{\xi }\approx 10^{16}$ GeV scale, associated with a huge vacuum energy density that may be responsible for the inflation of the early Universe.

    hep-phgr-qcPRD(2019)·48 citations
15. 15*

    Fingerprinting models of first-order phase transitions by the synergy between collider and gravitational-wave experiments

    Katsuya Hashino🇯🇵 · Ryusuke Jinno🇰🇷 · Mitsuru Kakizaki🇯🇵 · Shinya Kanemura🇯🇵 · Tomo Takahashi🇯🇵 · Masahiro Takimoto🇮🇱

    We investigate the sensitivity of future space-based interferometers such as LISA and DECIGO to the parameters of new particle physics models which drive a first-order phase transition in the early Universe. We first perform a Fisher matrix analysis on the quantities characterizing the gravitational wave spectrum resulting from the phase transition, such as the peak frequency and amplitude. We next perform a Fisher analysis for the quantities which determine the properties of the phase transition, such as the latent heat and the time dependence of the bubble nucleation rate. Since these quantities are determined by the model parameters of the new physics, we can estimate the expected sensitivities to such parameters. We illustrate this point by taking three new physics models for example: (1) models with additional isospin singlet scalars (2) a model with an extra real Higgs singlet, and (3) a classically conformal $B-L$ model. We find that future gravitational wave observations play complementary roles to future collider experiments in pinning down the parameters of new physics models driving a first-order phase transition.

    hep-phastro-ph.COPRD(2019)·87 citations
16. 16*

    QCD multiplet bases with arbitrary parton ordering

    Malin Sjodahl🇸🇪 · Johan Thorén🇸🇪

    We develop an algorithm for recursively constructing orthogonal multiplet bases for the color space of QCD, for any order of partons and any Nc. This recipe is then applied for explicitly constructing some of these bases. Using the bases, a corresponding set of Wigner 6j coefficients are calculated. The Wigner coefficients offer a method of using multiplet bases without resorting to the explicit expressions of the basis vectors, which lead to a significant speed-up compared to other methods of treating full color structure.

    hep-phhep-thJHEP(2018)·16 citations
17. 17*

    Extra Quarks and Bileptons in BSM Physics in a $331$ Model

    Claudio Coriano🇮🇹 · Antonio Costantini🇮🇹

    We describe some salient features of the $331_F$ (Frampton-Pisano-Pleitez) bilepton model, in which the constraints of anomaly cancelation require the number of generations to be three. In a class of six models, four of which characterised by a $\beta$ parameter describing the embedding of the hypercharge in the $SU(3{)}_L$ symmetry, a specific choice for $\beta$ allows bileptons in the spectrum, i.e. vectors and scalars of lepton numbers $\pm 2$. At the same time the model allows exotic quarks, with the third quark generation treated asymmetrically respect to the other two. Bileptons generate specific signatures in the form of multilepton final states in Drell-Yan like processes, with and without associated jets, which can be searched for at the LHC.

    hep-phEPJ Web Conf.(2018)·0 citations
18. 18*

    Bounds on extra dimensions from micro black holes in the context of the metastable Higgs vacuum

    Katherine J. Mack🇺🇸 · Robert McNees🇺🇸

    We estimate the rate at which collisions between ultra-high energy cosmic rays can form small black holes in models with extra dimensions. If recent conjectures about false vacuum decay catalyzed by black hole evaporation apply, the lack of vacuum decay events in our past light cone may place new bounds on the black hole formation rate and thus on the fundamental scale of gravity in these models. For theories with fundamental scale $E_{\ast }$ above the Higgs instability scale of the Standard Model, we find a lower bound on $E_{\ast }$ that is within about an order of magnitude of the energy where the cosmic ray spectrum begins to show suppression from the GZK effect. Otherwise, the abundant formation of semiclassical black holes with short lifetimes would likely initiate vacuum decay. Assuming a Higgs instability scale at the low end of the range compatible with experimental data, the excluded range is approximately $10^{17}\text{eV}\lesssim E_{\ast }\le 10^{18.8}\text{eV}$ for theories with $n=1$ extra dimension, narrowing to $10^{17}\text{eV}\lesssim E_{\ast }\le 10^{18.1}\text{eV}$ for $n=6$. These bounds rule out regions of parameter space that are inaccessible to collider experiments, small-scale gravity tests, or estimates of Kaluza-Klein processes in neutron stars and supernovae.

    hep-phastro-ph.COhep-thPRD(2019)·8 citations
19. 19*

    Extragalactic Searches for Dark Matter Annihilation

    Siddharth Mishra-Sharma🇺🇸

    We are at the dawn of a data-driven era in astrophysics and cosmology. A large number of ongoing and forthcoming experiments combined with an increasingly open approach to data availability offer great potential in unlocking some of the deepest mysteries of the Universe. Among these is understanding the nature of dark matter (DM)---one of the major unsolved problems in particle physics. Characterizing DM through its astrophysical signatures will require a robust understanding of its distribution in the sky and the use of novel statistical methods. The first part of this thesis describes the implementation of a novel statistical technique which leverages the "clumpiness" of photons originating from point sources (PSs) to derive the properties of PS populations hidden in astrophysical datasets. This is applied to data from the Fermi satellite at high latitudes ($|b|>30$\deg) to characterize the contribution of PSs of extragalactic origin. We find that the majority of extragalactic gamma-ray emission can be ascribed to unresolved PSs having properties consistent with known sources such as active galactic nuclei. This leaves considerably less room for significant dark matter contribution. The second part of this thesis poses the question: "what is the best way to look for annihilating dark matter in extragalactic sources?" and attempts to answer it by constructing a pipeline to robustly map out the distribution of dark matter outside the Milky Way using galaxy group catalogs. This framework is then applied to Fermi data and existing group catalogs to search for annihilating dark matter in extragalactic galaxies and clusters.

    ↳ astro-ph.COhep-ph1 citation
20. 20*

    Hydrodynamic fluctuations of entropy in one-dimensionally expanding system

    Tetsufumi Hirano🇯🇵 · Ryuichi Kurita🇯🇵 · Koichi Murase🇯🇵

    The fluctuation-dissipation relation tells that dissipation always accompanies with thermal fluctuations. Relativistic fluctuating hydrodynamics is used to study the effects of the thermal fluctuations in the hydrodynamic expansion of the quark-gluon plasma created in the high-energy nuclear collisions. We show that the thermal noise obeys the steady-state fluctuation theorem when (i) the time scales of the evolution of thermodynamic quantities are sufficiently longer than the relaxation time, and (ii) the thermal fluctuations of temperature are sufficiently small. The steady-state fluctuation theorem describes the distribution of the entropy which can be related to the multiplicity observed in high-energy nuclear collisions. As a consequence, we propose an upper bound to the multiplicity fluctuations which is useful to test the initial state models. We also numerically investigate breaking of the steady-state fluctuation theorem due to the non-vanishing relaxation time in real nuclear collisions.

    ↳ nucl-thcond-mat.stat-mechhep-phnucl-exNPA(2019)·20 citations
21. 21*

    Multi-feature universe: large parameter space cosmology and the swampland

    Deng Wang🇨🇳

    Under the belief that the universe should be multi-feature and informative, we employ a model-by-model comparison method to explore the possibly largest upper bound on the swampland constant $c$. Considering the interacting quintessence dark energy as the comparison model, we constrain the large parameter space interacting dark energy model, a 12-parameter extension to the $\Lambda$CDM cosmology, in light of current observations. We obtain the largest $2\sigma$ ($3\sigma$) bound so far, $c\lesssim 1.62$ $(1.94)$, which would allow the existences of a number of string theory models of dark energy such as 11-dimensional supergravity with double-exponential potential, $O(16)\times O(16)$ heterotic string and some Type II string compactifications. For inflationary models with concave potential, we find the $2\sigma$ ($3\sigma$) bound $c\lesssim 0.13$ $(0.14)$, which is still in strong tension with the string-based expectation $c\sim \mathcal{O}(1)$. However, combining Planck primordial non-Gaussianity with inflation constraints, it is interesting that the Dirac-Born-Infeld inflation with concave potential gives the $2\sigma$ ($3\sigma$) bound $c\lesssim 0.53$ $(0.58)$, which is now in a modest tension with the swampland conjecture. Using the Bayesian evidence as the model selection tool, it is very surprising that our 18-parameter multi-feature cosmology is extremely strongly favored over the $\Lambda$CDM model.

    ↳ astro-ph.COgr-qchep-phPhys.Dark Univ.(2020)·49 citations
22. 22*

    Cosmogenic Neutrinos Through the GRAND Lens Unveil the Nature of Cosmic Accelerators

    Klaes Møller🇩🇰 · Peter B. Denton🇩🇰 · Irene Tamborra🇩🇰

    The sources of cosmic rays with energies above 55 EeV are still mysterious. A guaranteed associated flux of ultra high energy neutrinos known as the cosmogenic neutrino flux will be measured by next generation radio facilities, such as the proposed Giant Radio Array for Neutrino Detection (GRAND). By using the orthogonal information provided by the cosmogenic neutrino flux, we here determine the prospects of GRAND to constrain the source redshift evolution and the chemical composition of the cosmic ray sources. If the redshift evolution is known, independently on GRAND's energy resolution, GRAND with 200,000 antennas will constrain the proton/iron fraction to the $\sim 5-10\%$ level after one year of data taking; on the other hand, if hints on the average source composition are given, GRAND will measure the redshift evolution of the sources to a $\sim 10\%$ uncertainty. However, the foreseen configuration of GRAND alone will not be able to break the degeneracy between redshift evolution of the sources and their composition. Our findings underline the discriminating potential of next generation radio array detectors and motivate further efforts in this direction.

    ↳ astro-ph.HEhep-exhep-phJCAP(2019)·40 citations
23. 23*

    New Results on Hard Probes in Heavy-Ion Collisions with ALICE

    Christian Klein-Bösing (for the ALICE Collaboration)🇩🇪

    Hard probes - final state particles related to an interaction with large momentum transfer or mass scale - play a distinguished role in the discovery and the study of the Quark-Gluon Plasma (QGP), a phase of deconfined quarks and gluons reached at high temperatures in heavy ion collisions. In heavy ion collisions, parton scatterings with a large momentum transfer ($1/Q\ll 1$ fm/$c$) occur prior to QGP formation and thus provide a source of coloured probe particles for the QGP created in the later stage of the reaction. The hard scattered partons and the subsequent parton shower interact strongly with the QGP and its constituents via elastic and radiative processes before hadronization into jets of observable particles. Thus, the comparison to jet and high-$p_T$ observables in pp (vacuum) potentially probes their modification due to medium effects. One of the key observables in the discovery and investigation of these jet modifications has been the nuclear modification factor $R_{AA}$, for which new results on charged particle production in different colliding systems are presented and the question of apparant suppression in peripheral Pb-Pb collisions is addressed. Fore more differential studies of the jet sub-structure and hence the parton shower evolution in the medium, recent results on jet grooming in heavy ion colisions are presented.

    ↳ hep-exhep-phnucl-exPoS(2018)·1 citation
24. 24*

    Fakeons, Microcausality And The Classical Limit Of Quantum Gravity

    Damiano Anselmi🇮🇹

    We elaborate on the idea of fake particle and study its physical consequences. When a theory contains fakeons, the true classical limit is determined by the quantization and a subsequent process of "classicization". One of the major predictions due to the fake particles is the violation of microcausality, which survives the classical limit. This fact gives hope to detect the violation experimentally. A fakeon of spin 2, together with a scalar field, is able to make quantum gravity renormalizable while preserving unitarity. We claim that the theory of quantum gravity emerging from this construction is the right one. By means of the classicization, we work out the corrections to the field equations of general relativity. We show that the finalized equations have, in simple terms, the form $⟨F⟩=ma$, where $⟨F⟩$ is an average that includes a little bit of "future".

    ↳ hep-thgr-qchep-phmath-ph+1Class.Quant.Grav.(2019)·81 citations
25. 25*

    The propagator seagull: general evaluation of a two loop diagram

    Barak Kol🇮🇱 · Ruth Shir🇮🇱

    We study a two loop diagram of propagator type with general parameters through the Symmetries of Feynman Integrals (SFI) method. We present the SFI group and equation system, the group invariant in parameter space and a general representation as a line integral over simpler diagrams. We present close form expressions for three sectors, each with three or four energy scales, for any spacetime dimension $d$ as well as the $ϵ$ expansion. We determine the singular locus and the diagram's value on it.

    ↳ hep-thhep-phJHEP(2019)·4 citations
26. 26*

    SymBuild: a package for the computation of integrable symbols in scattering amplitudes

    Vladimir Mitev🇩🇪 · Yang Zhang🇨🇭

    The article presents and documents the Mathematica package SymBuild. This package implements the computation and manipulation of integrable symbols appearing in various calculations in high-energy scattering amplitudes. By using Gröbner bases, implementing various simplifications and by the potential utilization of the C++ program SpaSM, integrable symbols in a large class of alphabets (including roots) can be computed to high weights.

    ↳ hep-thhep-ph12 citations
27. 27*

    Resolving the Weinberg Paradox with Topology

    John Terning🇺🇸 · Christopher B. Verhaaren🇺🇸

    Long ago Weinberg showed, from first principles, that the amplitude for a single photon exchange between an electric current and a magnetic current violates Lorentz invariance. The obvious conclusion at the time was that monopoles were not allowed in quantum field theory. Since the discovery of topological monopoles there has thus been a paradox. On the one hand, topological monopoles are constructed in Lorentz invariant quantum field theories, while on the other hand, the low-energy effective theory for such monopoles will reproduce Weinberg's result. We examine a toy model where both electric and magnetic charges are perturbatively coupled and show how soft-photon resummation for hard scattering exponentiates the Lorentz violating pieces to a phase that is the covariant form of the Aharonov-Bohm phase due to the Dirac string. The modulus of the scattering amplitudes (and hence observables) are Lorentz invariant, and when Dirac charge quantization is imposed the amplitude itself is also Lorentz invariant. For closed paths there is a topological component of the phase that relates to aspects of 4D topological quantum field theory.

    ↳ hep-thhep-phJHEP(2019)·35 citations
28. 28*

    Strongly Coupled Quintessence

    Guido D'Amico🇨🇭 · Nemanja Kaloper🇺🇸 · Albion Lawrence🇺🇸

    We present a family of consistent quantum field theories of monodromy quintessence in strong coupling, which can serve as benchmarks in modeling dark energy different from cosmological constant. These theories have discrete gauge symmetries which can protect them from quantum field theory and quantum gravity corrections, both perturbative and nonperturbative. The strong coupling effects, at scales $\text{ga}{\mathrm{mm}}^{-1}$, flatten the potential and activate operators with higher powers of derivatives. The predicted equation of state is close to, but not exactly equal to $-1$, thus being within reach of the (near!) future programs to explore the nature of dark energy.

    ↳ hep-thastro-ph.COgr-qchep-phPRD(2019)·52 citations
29. 29*

    Gravitational reheating through conformally coupled superheavy scalar particles

    Soichiro Hashiba🇯🇵 · Jun'ichi Yokoyama🇯🇵

    We calculate the number density and the energy density of a massive scalar particle conformally coupled to gravity produced by gravitational particle creation in the case the kination stage follows inflation. In this model, mode functions are derived in terms of exact or numerical solutions of the equation of motion without using the adiabatic approximation. We define the adiabatic vacuum in each stage and calculate the produced number density and the energy density. The resultant power spectra show that even the superheavy particle which is as heavy as or much heavier than the Hubble scale during inflation can be produced abundantly if the transition time scale from inflation to the kination stage is smaller than the inverse of the mass of the scalar field. We also give simple forms of the reheating temperature for two cases, one that the produced scalar particles decay instantly and the other that they decay when their energy density exceeds that of inflaton.

    ↳ gr-qchep-phhep-thJCAP(2019)·64 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.