Thu·Dec 6, 2018Thursday·December 6, 2018

1. 01*

   Probing Neutrino Dirac Mass in Left-Right Symmetric Models at the LHC and Next Generation Colliders

   Juan Carlos Helo🇨🇱 · Haolin Li🇨🇳 · Nicolas A. Neill🇨🇱 · Michael Ramsey-Musolf🇺🇸 · Juan Carlos Vasquez🇨🇱

   We assess the sensitivity of the LHC, its high energy upgrade, and a prospective 100 TeV hadronic collider to the Dirac Yukawa coupling of the heavy neutrinos in left-right symmetric models (LRSMs). We focus specifically on the trilepton final state in regions of parameter space yielding prompt decays of the right-handed gauge bosons ($W_R$) and neutrinos ($N_R$). In the minimal LRSM, the Dirac Yukawa couplings are completely fixed in terms of the mass matrices for the heavy and light neutrinos. In this case, the trilepton signal provides a direct probe of the Dirac mass term for a fixed $W_R$ and $N_R$ mass. We find that while it is possible to discover the $W_R$ at the LHC, probing the Dirac Yukawa couplings will require a 100 TeV $pp$ collider. We also show that the observation of the trilepton signal at the LHC would indicate the presence of a non-minimal LRSM scenario.

   hep-phhep-exPRD(2019)·24 citations
2. 02*

   Exotic Higgs Decays in Type-II 2HDMs at the LHC and Future 100 TeV Hadron Colliders

   Felix Kling🇺🇸 · Honglei Li🇨🇳 · Adarsh Pyarelal🇺🇸 · Huayang Song🇺🇸 · Shufang Su🇺🇸

   The exotic decay modes of non-Standard Model (SM) Higgses in models with extended Higgs sectors have the potential to serve as powerful search channels to explore the space of Two-Higgs Doublet Models (2HDMs) that cannot be studied effectively using conventional decay channels. Once kinematically allowed, heavy Higgses could decay into pairs of light non-SM Higgses, or a non-SM Higgs and a SM gauge boson, with branching fractions that dominate those of the conventional decay modes to SM particles. In this study, we focus on the prospects of probing exotic decay channels at the LHC and a future 100 TeV \emph{pp} collider in the context of Type-II 2HDMs. We study the three prominent exotic decay channels, A -> HZ, A -> H^+ W and H^+ -> HW, and find that a 100-TeV pp collider can probe the entire region of the Type-II 2HDM parameter space that survives current theoretical and experimental constraints with exotic decay branching fraction > 20%.

   hep-phJHEP(2019)·38 citations
3. 03*

   Searching for Heavy Neutral Leptons with Displaced Vertices at the LHC

   Asmaa Abada🇫🇷 · Nicolás Bernal🇨🇴 · Marta Losada🇨🇴 · Xabier Marcano🇫🇷

   Heavy Neutral Leptons are naturally present in many well-motivated extensions of the Standard Model. If their mass is of few dozens of GeVs, they can be long-lived and lead to events with displaced vertices, giving rise to promising signatures due to the low background. We revisit the opportunities offered by the LHC to discover these long-lived states via searches with displaced vertices. We study in particular the implication on the parameter space sensitivity when all mixings to active flavors are taken into account.

   hep-ph2 citations
4. 04*

   Phenomenology of the Partially Aligned 2HDM with leptonic decay of mesons

   A. Carrillo-Monteverde🇬🇧 · S. Gómez-Ávila🇲🇽 · R. Gómez-Rosas🇲🇽 · L. Lopez-Lozano🇲🇽 · A. Rosado🇲🇽

   In this paper we present a phenomenological analysis of the Partially Aligned Two Higgs Doublet Model (PA-2HDM) by using leptonic decays of mesons and $B_{d,s}^0$-${\bar{B}}_{d,s}^0$ mixing. We focus our attention in a scenario where the leading contribution to FCNC is given by the tree level interaction with the light pseudoscalar $A^0$ ($M_{A^0}\sim 250$ GeV). We show how an underlying flavor symmetry controls FCNC in the quark and lepton couplings with the pseudoscalar, without alignment between Yukawa matrices. Upper bounds on the free parameters are calculated in the context of the leptonic decays $B_{s,d}^0\to {\mu }^{+}{\mu }^{-}$ and $K_L^0\to {\mu }^{+}{\mu }^{-}$ and $B_{s,d}^0$ mixing. Also, our assumptions implies that bounds on New Physics contribution in the quark sector coming from $B_{s,d}^0$ mixing impose an upper bound on the parameters for the leptonic sector. Finally we give predictions of branching ratios for leptonic decay of mesons with FCNC and LFV.

   hep-phInt.J.Mod.Phys.A(2019)·3 citations
5. 05*

   Affinity of NJL${}_2$ and NJL${}_4$ model results on duality and pion condensation in chiral asymmetric dense quark matter

   T. G. Khunjua🇷🇺 · K.G. Klimenko🇷🇺 · R. N. Zhokhov-Larionov🇷🇺

   In this paper we investigate the phase structure of a (1+1) and (3+1)-dimensional quark model with four-quark interaction and in the presence of baryon (${\mu }_B$), isospin (${\mu }_I$) and chiral isospin (${\mu }_{I5}$) chemical potentials. It is shown that the chemical potential ${\mu }_{I5}$ promotes the appearance of the charged PC phase with nonzero baryon density. Results of both models are qualitatively the same, this fact enhances one's confidence in %the faith in the obtained predictions. It is established that in the large-$N_c$ limit ($N_c$ is the number of colored quarks) there exists a duality correspondence between the chiral symmetry breaking phase and the charged pion condensation one.

   hep-phhep-thEPJ Web Conf.(2018)·9 citations
6. 06*

   Gravitational wave and collider probes of a triplet Higgs sector with a low cutoff

   Mikael Chala🇬🇧 · Maria Ramos🇵🇹 · Michael Spannowsky🇬🇧

   We study the scalar triplet extension of the standard model with a low cutoff, preventing large corrections to the quadratic masses that would otherwise worsen the hierarchy problem. We explore the reach of LISA to test the parameter space region of the scalar potential (not yet excluded by Higgs to diphoton measurements) in which the electroweak phase transition is strongly first-order and produces sizeable gravitational waves. We also demonstrate that the collider phenomenology of the model is drastically different from its renormalizable counterpart. We study the reach of the LHC in ongoing searches and project bounds for the HL-LHC. Likewise, we develop a dedicated analysis to test the key but still unexplored signature of pair-production of charged scalars decaying to third-generation quarks: $pp\to t\overline{b}(\overline{t}b),b\overline{b}$. These results apply straightforwardly to other extensions of the Higgs sector such as the 2HDM/MSSM.

   hep-phEPJC(2019)·78 citations
7. 07*

   Recent developments in small-x resummation

   Marco Bonvini🇮🇹

   There has been a revived interest in small-x resummation in recent times. The main motivation was its success in describing small-x HERA data without the inclusion of non-perturbative corrections. In this contribution I will review the recent developments in the field.

   hep-phActa Phys.Polon.Supp.(2019)·5 citations
8. 08*

   Investigating two heavy neutral leptons neutrino seesaw mechanism at SHiP

   Marco Chianese🇳🇱 · Damiano F. G. Fiorillo🇮🇹 · Gennaro Miele🇮🇹 · Stefano Morisi🇮🇹

   One of the main purposes of SHiP experiment is to shed light on neutrino mass generation mechanisms like the so-called seesaw. We consider a minimal type-I seesaw neutrino mass mechanism model with two heavy neutral leptons (right-handed or sterile neutrinos) with arbitrary masses. Extremely high active-sterile mixing angle requires a correlation between the phases of the Dirac neutrino couplings. Actual experimental limits on the half-life of neutrinoless double beta decay $0\nu \beta \beta$-rate on the active-sterile mixing angle are not significative for SHiP.

   hep-phhep-exInt.J.Mod.Phys.A(2019)·14 citations
9. 09*

   Dynamics of the Polyakov loops in QCD

   R.A Abramchuk🇷🇺 · Z.V.Khaidukov🇷🇺 · Yu.A.Simonov🇷🇺

   A non-perturbative method of Field Correlators is applied to calculate the Polyakov loop dependence on temperature, $L(T)$, in the 2+1 flavor QCD with small quark masses, so the only relevant scale is the color-electric string tension $\sigma (T)$. Polyakov loop in the temperature range 100 MeV $\lesssim T\lesssim$ 400 MeV is expressed via the heavy-light meson mass that decreases with $T$ as $\sqrt{\sigma (T)}$. The latter is deduced from a gradually vanishing chiral condensate. The resulting $L(T)$ is in good agreement with recent lattice data.

   hep-phhep-lat4 citations
10. 10*

    TASI Lectures on Indirect Searches For Dark Matter

    Dan Hooper🇺🇸

    In these lectures, I describe a variety of efforts to identify or constrain the identity of dark matter by detecting the annihilation or decay products of these particles, or their effects. After reviewing the motivation for indirect searches, I discuss what we have learned about dark matter from observations of gamma rays, cosmic rays and neutrinos, as well as the cosmic microwave background. Measurements such as these have been used to significantly constrain a wide range of thermal relic dark matter candidates, in particular those with masses below a few hundred GeV. I also discuss a number of anomalies and excesses that have been interpreted as possible signals of dark matter, including the Galactic Center gamma-ray excess, the cosmic-ray antiproton excess, the cosmic-ray positron excess, and the 3.5 keV line. These lectures were originally presented as part of the 2018 Theoretical Advanced Study Institute (TASI) summer school on "Theory in an Era of Data". Although intended for advanced graduate students, these lectures may be useful for a wide range of physicists, astrophysicists and astronomers who wish to get an overview of the current state of indirect searches for dark matter.

    hep-phastro-ph.COastro-ph.GAastro-ph.HEPoS(2019)·63 citations
11. 11*

    The Roper resonance as a meson-baryon molecular state

    B. Golli🇸🇮

    The recently proposed mechanism for the formation of the Roper resonance, in which a dynamically generated state as well as a genuine three-quark resonant state play an equally important role, is confronted with the model proposed almost twenty years ago in which the Roper is pictured as a molecular state of the nucleon and the $\sigma$ meson.

    hep-phnucl-thBled Workshops Phys.(2018)·0 citations
12. 12*

    Pion-cloud contribution to the $N\to \Delta$ transition form factors

    Ju-Hyun Jung🇦🇹 · Wolfgang Schweiger🇦🇹

    We examine the contribution of the pion cloud to the electromagnetic $N\to \Delta$ transition form factors within a relativistic hybrid constituent-quark model. In this model baryons consist not only of the $3q$ valence component, but contain, in addition, a $3q\pi$ non-valence component. We start with constituent quarks which are subject to a scalar, isoscalar confining force. This leads to an $SU(6)$ spin-flavor symmetric spectrum with degenerate nucleon and Delta masses. Mass splitting is caused by pions which are assumed to couple directly to the quarks. The point-form of relativistic quantum mechanics is employed to achieve a relativistically invariant description of this system. The $N\to \Delta$ transition current is then determined from the one-photon exchange contribution to the $\Delta$ electroproduction amplitude. We will give predictions for the ratios $R_{EM}$ and $R_{SM}$ of electric to magnetic and Coulomb to magnetic form factors, which are supposed to be most sensitive to pion-cloud effects.

    hep-phSpringer Proc.Phys.(2020)·1 citation
13. 13*

    How Heavy can Neutralino Dark Matter be?

    Hajime Fukuda🇯🇵 · Feng Luo🇨🇳 · Satoshi Shirai🇯🇵

    What is the upper limit of the mass of the neutralino dark matter whose thermal relic is consistent with the observation? If the neutralino dark matter and colored sparticles are extremely degenerated in mass, with a mass difference less than the QCD scale, the dark matter annihilation is significantly increased and enjoys the "second freeze-out" after the QCD phase transition. In this case, the neutralino dark matter with a mass much greater than 100 TeV can realize the correct dark matter abundance. We study the dark matter abundance and its detection in the case of such highly degenerated mass spectrum of the neutralino dark matter and colored supersymmetric particles.

    hep-phJHEP(2019)·21 citations
14. 14*

    The CLIC Potential for New Physics

    J. de Blas🇮🇹 · R. Franceschini🇮🇹 · F. Riva🇨🇭 · P. Roloff🇨🇭 · U. Schnoor🇨🇭 · M. Spannowsky🇬🇧 · J. D. Wells🇺🇸 · A. Wulzer🇨🇭 · J. Zupan🇺🇸 · S. Alipour-Fard🇺🇸 · W. Altmannshofer🇺🇸 · A. Azatov🇮🇹 and 91 other authors

    The Compact Linear Collider (CLIC) is a mature option for the future of high energy physics. It combines the benefits of the clean environment of $e^{+}{e}^{-}$ colliders with operation at high centre-of-mass energies, allowing to probe scales beyond the reach of the Large Hadron Collider (LHC) for many scenarios of new physics. This places the CLIC project at a privileged spot in between the precision and energy frontiers, with capabilities that will significantly extend knowledge on both fronts at the end of the LHC era. In this report we review and revisit the potential of CLIC to search, directly and indirectly, for physics beyond the Standard Model.

    hep-phhep-exCERN Yellow Rep.Monogr.(2018)·279 citations
15. 15*

    Heavy-quark production with $k_t$-factorization: The importance of the sea-quark distribution

    Benjamin Guiot🇨🇱

    We discuss the fact that $k_t$-factorization calculations for heavy-quark production include only the $gg\to Q\bar{Q}$ contribution. The cases of fixed-flavor-number scheme and variable-flavor-number scheme calculations are analyzed separately. For the latter, we show that, similarly to the collinear factorization, the main contribution is given by the $Qg\to Qg$ process. In this scheme, calculations including only the $gg$ contribution should show a large discrepancy with the data. We show that, if they do not, it is because they include (effectively) a large $K$ factor.

    hep-phPRD(2019)·11 citations
16. 16*

    Modular $A_5$ Symmetry for Flavour Model Building

    P. P. Novichkov🇮🇹 · J. T. Penedo🇵🇹 · S. T. Petcov🇮🇹 · A. V. Titov🇬🇧

    In the framework of the modular symmetry approach to lepton flavour, we consider a class of theories where matter superfields transform in representations of the finite modular group ${\Gamma }_5\simeq A_5$. We explicitly construct a basis for the 11 modular forms of weight 2 and level 5. We show how these forms arrange themselves into two triplets and a quintet of $A_5$. We also present multiplets of modular forms of higher weight. Finally, we provide an example of application of our results, constructing two models of neutrino masses and mixing based on the supersymmetric Weinberg operator.

    hep-phhep-thJHEP(2019)·240 citations
17. 17*

    Small-scale structure from charged leptophilia

    Ottavia Balducci🇩🇪 · Stefan Hofmann🇩🇪 · Alexis Kassiteridis🇩🇪

    We consider a charged leptophilic extension of the Standard Model of particle physics as a minimal dark sector. It accomodates a WIMP paradigm at the TeV-scale that is sufficient to solve all small-scale problems of $\Lambda$CDM and explain the excess of highly energetic cosmic ray Standard Model electrons and positrons presented recently by the DAMPE collaboration. The predictive power of this model allows to test it in the near future.

    hep-phastro-ph.HE4 citations
18. 18*

    Scalar Dark Matter Probes the Scale of Non-locality

    Anish Ghoshal🇮🇹

    Scalar dark matter (DM) in a theory introduces hierarchy problems, and suffers from the inability to predict the preferred mass range for the DM. In a WIMP-like minimal scalar DM set-up we show that the infinite derivative theory can predict DM mass and its coupling. The scale of non-locality (M) in such a theory in its lower-most limit (constrained by LHC) implies a DM mass $\sim$ TeV and a coupling with the Standard Model (SM) Higgs ${\lambda }_{\mathrm{HS}}\sim 10^{-2}$. Planned DM direct detection experiments reaching such sensitivity in the DM will effectively translate into lower bounds on the scale at which the non-locality comes into the play. Self-interactions of DM and its impact on vacuum stability in this model are also discussed in the context.

    hep-phInt.J.Mod.Phys.A(2019)·16 citations
19. 19*

    4D ensembles of percolating center vortices and chains

    L. E. Oxman🇧🇷

    In this work, we review a recently proposed measure to compute center-element averages in a mixed ensemble of center vortices and chains with non-Abelian d.o.f. and monopole fusion. When center vortices percolate and monopoles condense, the average is captured by a saddle point and collective modes in a YMH model. In this manner, the Lüscher term, confining flux tubes with N-ality and confined gluons were accommodated in an ensemble picture.

    ↳ hep-thhep-phPoS(2019)·2 citations
20. 20*

    Updated CLIC luminosity staging baseline and Higgs coupling prospects

    Aidan Robson🇬🇧 · Philipp Roloff🇨🇭

    An updated luminosity staging baseline for CLIC is presented. Assuming accelerator ramp-up and up-time scenarios that are harmonized with those of other potential future colliders, CLIC will deliver 1 ab^-1 at sqrt(s)=380 GeV, 2.5 ab^-1 at sqrt(s)=1.5 TeV, and 5 ab^-1 at sqrt(s)=3 TeV. The complete programme will take 25-30 years. The baseline scenario for luminosity sharing between the two electron beam polarisation states is also discussed. Updated Higgs coupling sensitivities are given for this new luminosity staging baseline.

    ↳ hep-exhep-ph86 citations
21. 21*

    Radiative corrections and Lorentz violation

    A. F. Ferrari🇧🇷 · J. R. Nascimento🇧🇷 · A. Yu. Petrov🇧🇷

    Radiative corrections in Lorentz violating (LV) models have already received a lot of attention in the literature in recent years, with many instances where a LV operator in one sector of the Standard Model Extension (SME) generates, via loop corrections, one of the LV coefficients in the photon sector, which is probably the most understood and well constrained part of the SME. In many of these works, however, the now standard notation of the SME is not used, which can obscure the comparison of different results, and their possible phenomenological relevance. In this work, we fill this gap, trying to build up a more general perspective on the topic, bringing many of the results to the SME conventional notation and commenting on their possible phenomenological relevance. We uncover one example where a result already presented in the literature can be used to place a stronger bound on the temporal component of the b_{\mu} coefficient of the fermion sector of the SME.

    ↳ hep-thhep-phEPJC(2020)·46 citations
22. 22*

    Formation and Evolution of Primordial Black Hole Binaries in the Early Universe

    Martti Raidal🇪🇪 · Christian Spethmann🇪🇪 · Ville Vaskonen🇬🇧 · Hardi Veermäe🇪🇪

    The abundance of primordial black holes (PBHs) in the mass range $0.1-10^3{M}_{\odot }$ can potentially be tested by gravitational wave observations due to the large merger rate of PBH binaries formed in the early universe. To put the estimates of the latter on a firmer footing, we first derive analytical PBH merger rate for general PBH mass functions while imposing a minimal initial comoving distance between the binary and the PBH nearest to it, in order to pick only initial configurations where the binary would not get disrupted. We then study the formation and evolution of PBH binaries before recombination by performing N-body simulations. We find that the analytical estimate based on the tidally perturbed 2-body system strongly overestimates the present merger rate when PBHs comprise all dark matter, as most initial binaries are disrupted by the surrounding PBHs. This is mostly due to the formation of compact N-body systems at matter-radiation equality. However, if PBHs make up a small fraction of the dark matter, $f_{\mathrm{PBH}}\lesssim 10\%$, these estimates become more reliable. In that case, the merger rate observed by LIGO imposes the strongest constraint on the PBH abundance in the mass range $2-160M_{\odot }$. Finally, we argue that, even if most initial PBH binaries are perturbed, the present BH-BH merger rate of binaries formed in the early universe is larger than $\mathcal{O}(10){\mathrm{Gpc}}^{-3}{\mathrm{yr}}^{-1}{f}_{\mathrm{PBH}}^3$

    ↳ astro-ph.COastro-ph.HEhep-phJCAP(2019)·394 citations
23. 23*

    Baryonic or quarkyonic matter?

    Owe Philipsen🇩🇪 · Jonas Scheunert🇩🇪

    During the last years it has become possible to address the cold and dense regime of QCD directly for sufficiently heavy quarks, where combined strong coupling and hopping expansions are convergent and a 3d effective theory can be derived, which allows to control the sign problem either in simulations or by fully analytic calculations. In this contribution we review the effective theory and study the $N_c$-dependence of the nuclear liquid gas transition, as well as the equation of state of baryonic matter in the strong coupling limit. We find the transition to become more strongly first order with growing $N_c$, suggesting that in the large $N_c$ limit its critical endpoint moves to high temperatures to connect with the deconfinement transition. Furthermore, to leading and next-to-leading order in the strong coupling and hopping expansions, respectively, the pressure is found to scale as $p\sim N_c$. This suggests that baryonic and quarkyonic matter might be the same at nuclear densities. Further work is needed to see whether this result is stable under gauge corrections.

    ↳ hep-lathep-phnucl-thPoS(2018)·5 citations
24. 24*

    Lower bound on the proton charge radius from electron scattering data

    Franziska Hagelstein (AEC Bern)🇨🇭 · Vladimir Pascalutsa (JGU Mainz)🇩🇪

    The proton charge-radius determinations from the electromagnetic form-factor measurements in electron-proton scattering require an extrapolation to zero momentum transfer ($Q^2=0$) which is prone to model-dependent assumptions. We show that the data at finite momentum transfer can be used to establish a rigorous lower bound on the proton charge radius. Using the available $ep$ data at low $Q^2$, we obtain $R_E>0.850(1)$ fm as the lower bound on the proton radius. This reaffirms the discrepancy between the $ep$ and muonic-hydrogen values, while bypassing the model-dependent assumptions that go into the fitting and extrapolation of the $ep$ data.

    ↳ nucl-thhep-phnucl-exPLB(2019)·7 citations
25. 25*

    NLO Productions of $\omega$ and $K_{\mathrm{S}}^0$ with a Global Extraction of the Jet Transport Parameter in Heavy Ion collisions

    Guo-Yang Ma🇨🇳 · Wei Dai🇨🇳 · Ben-Wei Zhang🇨🇳 · En-Ke Wang🇨🇳

    In this work, we pave the way to calculate the productions of $\omega$ and $K_{\mathrm{S}}^0$ mesons at large $p_T$ in p+p and A+A collisions at the RHIC and the LHC. The $\omega$ meson fragmentation functions (FFs) in vacuum at next-to-leading order (NLO) are obtained by evolving NLO DGLAP evolution equations with rescaled $\omega$ FFs at initial scale $Q_0^2=1.5$ GeV${}^2$ from a broken SU(3) model, and the $K_{\mathrm{S}}^0$ FFs in vacuum are taken from AKK08 parametrization directly. Within the framework of the NLO pQCD improved parton model, we make good descriptions of the experimental data on $\omega$ and $K_{\mathrm{S}}^0$ in p+p both at the RHIC and the LHC. With the higher-twist approach to take into account the jet quenching effect by medium modified FFs, the nuclear modification factors for $\omega$ meson and $K_{\mathrm{S}}^0$ meson at the RHIC and the LHC are presented with different sets of jet transport coefficient ${\hat{q}}_0$. Then we make a global extraction of ${\hat{q}}_0$ at the RHIC and the LHC by confronting our model calculations with all available data on 6 identified mesons: ${\pi }^0$, $\eta$, ${\rho }^0$, $\varphi$, $\omega$, and $K_{\mathrm{S}}^0$. The minimum value of the total ${\chi }^2/d.o.f$ for productions of these mesons gives the best value of ${\hat{q}}_0=0.5\mathrm{Ge}{\mathrm{V}}^2/fm$ for Au+Au collisions with $\sqrt{s_{\mathrm{NN}}}=200$ GeV at the RHIC, and ${\hat{q}}_0=1.2\mathrm{Ge}{\mathrm{V}}^2/fm$ for Pb+Pb collisions with $\sqrt{s_{\mathrm{NN}}}=2.76$ TeV at the LHC respectively, with the QGP spacetime evolution given by an event-by-event viscous hydrodynamics model IEBE-VISHNU. With these global extracted values of ${\hat{q}}_0$, the nuclear modification factors of ${\pi }^0$, $\eta$, ${\rho }^0$, $\varphi$, $\omega$, and $K_{\mathrm{S}}^0$ in A+A collisions are presented, and predictions of yield ratios such as $\omega /{\pi }^0$ and $K_{\mathrm{S}}^0/{\pi }^0$ at large $p_T$ in heavy-ion collisions at the RHIC and the LHC are provided.

    ↳ nucl-thhep-phEPJC(2019)·30 citations
26. 26*

    Topological susceptibility at $T>T_{\mathrm{c}}$ from master-field simulations of the SU(3) gauge theory

    Leonardo Giusti🇮🇹 · Martin Lüscher🇨🇭

    The topological susceptibility is computed in the SU(3) gauge theory at temperatures $T$ above the critical temperature $T_{\mathrm{c}}$ using master-field simulations of very large lattices, where the infamous topology-freezing issue is effectively bypassed. Up to $T=2.0T_{\mathrm{c}}$ no unusually large lattice effects are observed and the results obtained in the continuum limit confirm the expected rapid decay of the susceptibility with increasing temperature. As a byproduct, the reference gradient-flow time $t_0$ is determined in the range of lattice spacings from $0.023$ to $0.1\mathrm{fm}$ with a precision of 2 per mille.

    ↳ hep-lathep-phhep-thEPJC(2019)·64 citations
27. 27*

    Unresolved Gamma-Ray Sky through its Angular Power Spectrum

    M. Ackermann🇩🇪 · M. Ajello🇺🇸 · L. Baldini🇮🇹 · J. Ballet🇫🇷 · G. Barbiellini🇮🇹 · D. Bastieri🇮🇹 · R. Bellazzini🇮🇹 · E. Bissaldi🇮🇹 · R. D. Blandford🇺🇸 · R. Bonino🇮🇹 · E. Bottacini🇺🇸 · J. Bregeon🇫🇷 and 98 other authors

    The gamma-ray sky has been observed with unprecedented accuracy in the last decade by the Fermi large area telescope (LAT), allowing us to resolve and understand the high-energy Universe. The nature of the remaining unresolved emission (unresolved gamma-ray background, UGRB) below the LAT source detection threshold can be uncovered by characterizing the amplitude and angular scale of the UGRB fluctuation field. This work presents a measurement of the UGRB autocorrelation angular power spectrum based on eight years of Fermi LAT Pass 8 data products. The analysis is designed to be robust against contamination from resolved sources and noise systematics. The sensitivity to subthreshold sources is greatly enhanced with respect to previous measurements. We find evidence (with $\sim$3.7$\sigma$ significance) that the scenario in which two classes of sources contribute to the UGRB signal is favored over a single class. A double power law with exponential cutoff can explain the anisotropy energy spectrum well, with photon indices of the two populations being 2.55 $\pm$ 0.23 and 1.86 $\pm$ 0.15.

    ↳ astro-ph.HEastro-ph.COhep-phPRL(2018)·54 citations
28. 28*

    Two-loop kite master integral for a correlator of two composite vertices

    S. V. Mikhailov🇷🇺 · N. Volchanskiy🇷🇺

    We consider the most general two-loop massless correlator $I(n_1,n_2,n_3,n_4,n_5;x,y;D)$ of two composite vertices with the Bjorken fractions $x$ and $y$ for arbitrary indices $\{n_i\}$ and space-time dimension $D$; this correlator is represented by a "kite" diagram. The correlator $I(\{n_i\};x,y;D)$ is the generating function for any scalar Feynman integrals related to this kind of diagrams. We calculate $I(\{n_i\};x,y;D)$ and its Mellin moments in a direct way by evaluating hypergeometric integrals in the $\alpha$ representation. The result for $I(\{n_i\};x,y;D)$ is given in terms of a double hypergeometric series -- the Kampé de Férriet function. In some particular but still quite general cases it reduces to a sum of generalized hypergeometric functions ${}_3{F}_2$. The Mellin moments can be expressed through generalized Lauricella functions, which reduce to the Kampé de Férriet functions in several physically interesting situations. A number of Feynman integrals involved and relations for them are obtained.

    ↳ hep-thhep-phJHEP(2019)·7 citations
29. 29*

    Search for a Dark Photon in Electro-Produced $e^{+}{e}^{-}$ Pairs with the Heavy Photon Search Experiment at JLab

    P. H. Adrian · N. A. Baltzell · M. Battaglieri · M. Bondí · S. Boyarinov · S. Bueltmann · V. D. Burkert · D. Calvo · M. Carpinelli · A. Celentano · G. Charles · L. Colaneri and 65 other authors

    The Heavy Photon Search experiment took its first data in a 2015 engineering run using a 1.056 GeV, 50 nA electron beam provided by CEBAF at the Thomas Jefferson National Accelerator Facility, searching for an electro-produced dark photon. Using 1.7 days (1170 nb${}^{-1}$) of data, a search for a resonance in the $e^{+}{e}^{-}$ invariant mass distribution between 19 and 81 MeV/c${}^2$ showed no evidence of dark photon decays above the large QED background, confirming earlier searches and demonstrating the full functionality of the experiment. Upper limits on the square of the coupling of the dark photon to the Standard Model photon are set at the level of 6$\times 10^{-6}$. In addition, a search for displaced dark photon decays did not rule out any territory but resulted in a reliable analysis procedure that will probe hitherto unexplored parameter space with future, higher luminosity runs.

    ↳ hep-exhep-phPoS(2019)·4 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.