Thu·Dec 20, 2018Thursday·December 20, 2018

1. 01*

   Collider phenomenology of a unified leptoquark model

   Thomas Faber🇩🇪 · Matěj Hudec🇨🇿 · Helena Kolešová🇳🇴 · Yang Liu🇩🇪 · Michal Malinský🇨🇿 · Werner Porod🇩🇪 · Florian Staub🇩🇪

   We demonstrate that in a recently proposed unified leptoquark model based on the gauge group $SU(4{)}_C\times SU(2{)}_L\times U(1{)}_R$ significant deviations from the Standard Model values of $R_K$ and $R_{K^{\ast }}$ can be accommodated without any need of extra heavy fermions. Low energy data, in particular lepton flavour violating $\mu$ decays and $K_L\to e\mu$, severely constrain the available parameter space. We show that in the allowed part of the parameter space (i) some of the lepton-flavour-violating tau decay branching ratios are predicted to be close to their current experimental limits. (ii) The underlying scalar leptoquarks can be probed at the LHC via their dominant decay modes into tau-leptons and electrons and the third generation quarks. (iii) The constraints from meson oscillations imply that the masses of scalar gluons, another pair of coloured multiplets around, have to be bigger than around 15 TeV and, thus, they can be probed only at a future 100 TeV collider. In both neutral and charged variants, these scalars decay predominantly into third generation quarks, with up to $O$(10\%) branching ratios into family-mixed final states. Besides that, we comment on the phenomenology of the scalar gluons in the current scenarios in the case that the $B$-decay anomalies eventually disappear.

   hep-phPRD(2020)·31 citations
2. 02*

   Precise predictions for ${\Lambda }_b\to {\Lambda }_c$ semileptonic decays

   Florian U. Bernlochner🇩🇪 · Zoltan Ligeti🇺🇸 · Dean J. Robinson🇺🇸 · William L. Sutcliffe🇩🇪

   We calculate the ${\Lambda }_b\to {\Lambda }_c\ell \nu$ form factors and decay rates for all possible $b\to c\ell \bar{\nu }$ four-Fermi interactions beyond the Standard Model, including nonzero charged lepton masses and terms up to order ${\alpha }_s{\Lambda }_{\text{QCD}}/m_{c,b}$ and ${\Lambda }_{\text{QCD}}^2/m_c^2$ in the heavy quark effective theory. At this order, we obtain model independent predictions for semileptonic ${\Lambda }_b\to {\Lambda }_c$ decays in terms of only two unknown sub-subleading Isgur-Wise functions, which can be determined from fitting LHCb and lattice QCD data. We thus obtain model independent results for ${\Lambda }_b\to {\Lambda }_c\ell \bar{\nu }$ decays, including predictions for the ratio $R({\Lambda }_c)=\mathcal{B}({\Lambda }_b\to {\Lambda }_c\tau \bar{\nu })/\mathcal{B}({\Lambda }_b\to {\Lambda }_c\mu \bar{\nu })$ in the presence of new physics, that are more precise than prior results in the literature, and systematically improvable with better data on the decays with $\mu$ (or $e$) in the final state. We also explore tests of factorization in ${\Lambda }_b\to {\Lambda }_c\pi$ decays, and emphasize the importance of measuring at LHCb the double differential rate $d^2\Gamma ({\Lambda }_b\to {\Lambda }_c\ell \bar{\nu })/(d{q}^{2}d\cos \theta )$, in addition to the $q^2$ spectrum.

   hep-phPRD(2019)·89 citations
3. 03*

   New global fits to $b\to s$ data with all relevant parameters

   T. Hurth🇩🇪 · A. Arbey🇫🇷 · F. Mahmoudi🇫🇷 · S. Neshatpour🇮🇷

   The LHCb experiment has made several measurements in $b\to s$ transitions which indicate tensions with the Standard Model predictions. Assuming the source of these tensions to be new physics, we present new global fits to all Wilson coefficients which can effectively receive beyond the Standard Model contributions. While the theoretically clean ratios $R_{K^{(\ast )}}$ which are sensitive to lepton flavour non-universality may unambiguously establish lepton non-universal new physics in the near future, most of the other tensions with the SM in the $b\to s$ data, in particular in the angular observables of the $B\to K^{\ast }\mu \mu$ decay and in the branching ratio of the $B_s\to \varphi \mu \mu$ decay, depend on the estimates of non-factorisable power corrections. Therefore, we also analyse the dependence of the new global fit on these corrections.

   hep-phNucl.Part.Phys.Proc.(2018)·6 citations
4. 04*

   Opportunities in Flavour Physics at the HL-LHC and HE-LHC

   A. Cerri🇬🇧 · V.V. Gligorov🇫🇷 · S. Malvezzi🇮🇹 · J. Martin Camalich🇪🇸 · J. Zupan🇺🇸 · S. Akar🇺🇸 · J. Alimena🇺🇸 · B.C. Allanach🇬🇧 · W. Altmannshofer🇺🇸 · L. Anderlini🇮🇹 · F. Archilli🇳🇱 · P. Azzi🇮🇹 and 291 other authors

   Motivated by the success of the flavour physics programme carried out over the last decade at the Large Hadron Collider (LHC), we characterize in detail the physics potential of its High-Luminosity and High-Energy upgrades in this domain of physics. We document the extraordinary breadth of the HL/HE-LHC programme enabled by a putative Upgrade II of the dedicated flavour physics experiment LHCb and the evolution of the established flavour physics role of the ATLAS and CMS general purpose experiments. We connect the dedicated flavour physics programme to studies of the top quark, Higgs boson, and direct high-$p_T$ searches for new particles and force carriers. We discuss the complementarity of their discovery potential for physics beyond the Standard Model, affirming the necessity to fully exploit the LHC's flavour physics potential throughout its upgrade eras.

   hep-phhep-exCERN Yellow Rep.Monogr.(2019)·321 citations
5. 05*

   Selection rules for light-by-light scattering in strong magnetic field

   A.E. Shabad🇷🇺

   Selection rules that follow from CP- and 4-momentum conservation are listed for head-on light-by-light scattering in strong magnetic field taking into account nontrivial dispersion laws of different photon eigenmodes.

   hep-ph0 citations
6. 06*

   New physics searches with heavy-ion collisions at the LHC

   Roderik Bruce🇨🇭 · David d'Enterria🇨🇭 · Albert de Roeck🇨🇭 · Marco Drewes🇧🇪 · Glennys R. Farrar🇺🇸 · Andrea Giammanco🇧🇪 · Oliver Gould🇫🇮 · Jan Hajer🇧🇪 · Lucian Harland-Lang🇬🇧 · Jan Heisig🇧🇪 · John M. Jowett🇨🇭 · Sonia Kabana🇫🇷 and 9 other authors

   This document summarises proposed searches for new physics accessible in the heavy-ion mode at the CERN Large Hadron Collider (LHC), both through hadronic and ultraperipheral $\gamma \gamma$ interactions, and that have a competitive or, even, unique discovery potential compared to standard proton-proton collision studies. Illustrative examples include searches for new particles -- such as axion-like pseudoscalars, radions, magnetic monopoles, new long-lived particles, dark photons, and sexaquarks as dark matter candidates -- as well as new interactions, such as non-linear or non-commutative QED extensions. We argue that such interesting possibilities constitute a well-justified scientific motivation, complementing standard quark-gluon-plasma physics studies, to continue running with ions at the LHC after the Run-4, i.e. beyond 2030, including light and intermediate-mass ion species, accumulating nucleon-nucleon integrated luminosities in the accessible fb${}^{-1}$ range per month.

   hep-phhep-exnucl-exnucl-thJ.Phys.G(2020)·95 citations
7. 07*

   Effect of Rope Hadronisation on Strangeness Enhancement in p$-$p collisions at LHC energies

   Ranjit Nayak🇮🇳 · Subhadip Pal🇮🇳 · Sadhana Dash🇮🇳

   The p$-$p collisions at high multiplicity at LHC show small scale collective effects similar to that observed in heavy ion collisions such as enhanced production of strange and multi-strange hadrons, long range azimuthal correlations, etc. The observation of strangeness enhancement in p$-$p collisions at at $\sqrt{s}$ = 7 TeV and 13 TeV as measured by ALICE experiment is explored using Pythia8 event generator within the framework of microscopic rope hadronization model which assumes the formation of ropes due to overlapping of strings in high multiplicity environment. The transverse momentum ($p_T$) spectra shape and its hardening with multiplicity is well described by the model. The mechanism of formation of ropes also described the observed experimental strangeness enhancement for higher multiplicity classes in p$-$p collisions at 7 TeV and 13 TeV. The enhancement with multiplicity is further investigated by studying the mean $p_T$ ($<p_T>$) and the integrated yields ($<dN/dy>$ ) of strange and multi-strange hadrons and comparing the predictions to the measured data at LHC for 7 TeV and 13 TeV.

   hep-phPRD(2019)·37 citations
8. 08*

   Representing seesaw neutrino models and their motion in lepton flavour space

   Pasquale Di Bari🇬🇧 · Michele Re Fiorentin🇮🇹 · Rome Samanta🇬🇧

   We discuss how seesaw neutrino models can be graphically represented in lepton flavour space. We examine various popular models and show how this representation helps understanding their properties and connection with experimental data showing in particular how certain texture zero models are ruled out. We also introduce a new matrix, the bridging matrix, that brings from the light to the heavy neutrino mass flavour basis, showing how this is related to the orthogonal matrix and how different quantities are easily expressed through it. We then show how one can randomly generate orthogonal and leptonic mixing matrices uniformly covering all flavour space in an unbiased way (Haar-distributed matrices). Using the isomorphism between the group of complex rotations and the Lorentz group, we also introduce the conceptof Lorentz boost in flavour space for a seesaw model and how this has an insightful physical interpretation. Finally, as a significant application, we consider $N_2$-leptogenesis. Using current experimental values of low energy neutrino parameters, we show that the probability that at least one flavoured decay parameter of the lightest right-handed neutrino is smaller than unity is about $49\%$ (to be compared with the tiny probability that the total decay parameter is smaller than unity, $P(K_{\mathrm{I}}<1)\sim 0.1\%$, confirming the crucial role played by flavour effects). On the other hand when $m_1\gtrsim 0.1\mathrm{eV}$ this probability reduces to less than $5\%$, showing how also $N_2$-leptogenesis disfavours degenerate light neutrinos.

   hep-phJHEP(2019)·13 citations
9. 09*

   Exact Top Yukawa corrections to Higgs boson decay into bottom quarks

   Amedeo Primo🇨🇭 · Gianmarco Sasso🇮🇹 · Gabor Somogyi🇭🇺 · Francesco Tramontano🇮🇹

   In this letter we present the results of the exact computation of contributions to the Higgs boson decay into bottom quarks that are proportional to the top Yukawa coupling. Our computation demonstrates that approximate results already available in the literature turn out to be particularly accurate for the three physical mass values of the Higgs boson, the bottom and top quarks. Furthermore, contrary to expectations, the impact of these corrections on differential distributions relevant for the searches of the Higgs boson decaying into bottom quarks at the Large Hadron Collider is rather small.

   hep-phhep-exPRD(2019)·45 citations
10. 10*

    Charged lepton beams as a source of effective neutrinos

    I. Alikhanov🇷🇺

    Neutrinos are likely the most poorly understood basic constituents of the Standard Model. In order to investigate precisely their interactions one should be able to create high intensity and well-collimated neutrino beams with known flavor compositions. This is a challenging problem for neutrino experiments. We propose a method of studying neutrino interactions based on the fact that a charged lepton is able to manifest itself effectively, with a certain probability, as a neutrino. The effective neutrino method may provide an additional tool for probing neutrino-induced reactions at $e^{+}{e}^{-}$ and $ep$ colliders as well as at other facilities that use charged lepton beams. We derive the distributions of the effective neutrinos in the charged leptons and give examples of application of the method to electron-positron collisions.

    hep-phEPL(2020)·2 citations
11. 11*

    Scalar Electroweak Multiplet Dark Matter

    Wei Chao🇨🇳 · Gui-Jun Ding🇨🇳 · Xiao-Gang He🇹🇼 · Michael Ramsey-Musolf🇺🇸

    We revisit the theory and phenomenology of scalar electroweak multiplet thermal dark matter. We derive the most general, renormalizable scalar potential, assuming the presence of the Standard Model Higgs doublet, $H$, and an electroweak multiplet $\Phi$ of arbitrary SU(2${)}_L$ rank and hypercharge, $Y$. We show that, in general, the $\Phi$-$H$ Higgs portal interactions depend on three, rather than two independent couplings as has been previously considered in the literature. For the phenomenologically viable case of $Y=0$ multiplets, we focus on the septuplet and quintuplet cases, and consider the interplay of relic density and spin-independent direct detection cross section. We show that both the relic density and direct detection cross sections depend on a single linear combination of Higgs portal couplings, ${\lambda }_{\mathrm{eff}}$. For ${\lambda }_{\mathrm{eff}}\sim \mathcal{O}(1)$, present direct detection exclusion limits imply that the neutral component of a scalar electroweak multiplet would comprise a subdominant fraction of the observed DM relic density.

    hep-phJHEP(2019)·39 citations
12. 12*

    Beyond the Standard Model Physics at the HL-LHC and HE-LHC

    X. Cid Vidal🇪🇸 · M. D'Onofrio🇬🇧 · P. J. Fox🇺🇸 · R. Torre🇨🇭 · K. A. Ulmer🇺🇸 · A. Aboubrahim🇺🇸 · A. Albert🇩🇪 · J. Alimena🇺🇸 · B. C. Allanach🇬🇧 · C. Alpigiani🇺🇸 · M. Altakach🇫🇷 · S. Amoroso🇩🇪 and 285 other authors

    This is the third out of five chapters of the final report [1] of the Workshop on Physics at HL-LHC, and perspectives on HE-LHC [2]. It is devoted to the study of the potential, in the search for Beyond the Standard Model (BSM) physics, of the High Luminosity (HL) phase of the LHC, defined as $3{\mathrm{ab}}^{-1}$ of data taken at a centre-of-mass energy of $14\mathrm{TeV}$, and of a possible future upgrade, the High Energy (HE) LHC, defined as $15{\mathrm{ab}}^{-1}$ of data at a centre-of-mass energy of $27\mathrm{TeV}$. We consider a large variety of new physics models, both in a simplified model fashion and in a more model-dependent one. A long list of contributions from the theory and experimental (ATLAS, CMS, LHCb) communities have been collected and merged together to give a complete, wide, and consistent view of future prospects for BSM physics at the considered colliders. On top of the usual standard candles, such as supersymmetric simplified models and resonances, considered for the evaluation of future collider potentials, this report contains results on dark matter and dark sectors, long lived particles, leptoquarks, sterile neutrinos, axion-like particles, heavy scalars, vector-like quarks, and more. Particular attention is placed, especially in the study of the HL-LHC prospects, to the detector upgrades, the assessment of the future systematic uncertainties, and new experimental techniques. The general conclusion is that the HL-LHC, on top of allowing to extend the present LHC mass and coupling reach by $20-50\%$ on most new physics scenarios, will also be able to constrain, and potentially discover, new physics that is presently unconstrained. Moreover, compared to the HL-LHC, the reach in most observables will generally more than double at the HE-LHC, which may represent a good candidate future facility for a final test of TeV-scale new physics.

    hep-phhep-exCERN Yellow Rep.Monogr.(2019)·319 citations
13. 13*

    Magnetic moments of the spin-1/2 singly charmed baryons in covariant baryon chiral perturbation theory

    Shi-Rui Xiabng🇨🇳 · Yang Xiao🇨🇳 · Li-Sheng Geng🇨🇳

    Recent experimental advances have reignited theoretical interests in heavy-flavor hadrons. In this work, we study the magnetic moments of the spin-1/2 singly charmed baryons up to the next-to-leading order in covariant baryon chiral perturbation theory with the extended-on-mass-shell renormalization scheme. The pertinent low energy constants $g_{1-4}$ are fixed with the help of the quark model and the heavy quark spin flavor symmetry, while the remaining $d_2$, $d_3$, $d_5$ and $d_6$ are determined by fitting to the lattice QCD pion-mass dependent data. We study the magnetic moments as a function of $m_{\pi }^2$ and compare our results with those obtained in the heavy baryon chiral perturbation theory. We find that the loop corrections induced by the anti-triplet states are dominated by the baryon pole diagram. In addition, we predict the magnetic moments of the spin-1/2 singly charmed baryons and compare them with those of other approaches.

    hep-phhep-latPRD(2019)·26 citations
14. 14*

    Constraining the Inert Doublet Model using Vector Boson Fusion

    Daniel Dercks🇩🇪 · Tania Robens🇭🇷

    In this work, we use a recast of the Run II search for invisible Higgs decays within Vector Boson Fusion to constrain the parameter space of the Inert Doublet model, a two Higgs doublet model with a dark matter candidate. When including all known theoretical as well as collider constraints, we find that the above can rule out a relatively large part in the mH-lambda345 parameter space, for dark scalar masses mH <= 100 GeV. Including the latest dark matter constraints, a smaller part of parameter space remains which is solely excluded from the above analysis. We also discuss the sensitivity of monojet searches and multilepton final states from Run II.

    hep-phEPJC(2019)·60 citations
15. 15*

    Resolving $B$-meson anomalies by flavor-dependent gauged symmetries $\prod _{i=1}^{3}U(1{)}_{B_i-L_i}$

    Chao-Qiang Geng🇨🇳 · Hiroshi Okada🇰🇷

    We propose a model with flavor dependent gauged symmetries of $\prod _{i=1}^{3}U(1{)}_{B_i-L_i}$ with $i$ the family indices. After formulating the renormalizable Yukawa Lagrangian, Higgs potential and kinetic term, we study the lepton sector based on a successful two-zero texture without introducing extra scalar bosons to avoid the dangerous Goldstone bosons. In particular, we discuss the muon related phenomenologies via additional neutral gauge bosons. In our numerical analysis, we explore the allowed parameter space, in which the anomaly of $B\to K^{\ast }\bar{\mu }\mu$ can be explained.

    hep-ph7 citations
16. 16*

    Neutrinos and the challenges of particle physics

    J. W. F. Valle🇪🇸

    I present a grand view of some of the main particle physics challenges from a neutrino perspective. After a brief review of the current status of neutrino physics, I illustrate the possible role neutrinos can play in the elucidation of various puzzles in particle physics and cosmology, for which the Standard Model offers no answer.

    hep-phastro-ph.COhep-exPoS(2019)·6 citations
17. 17*

    Understanding wide jet suppression in data through the hybrid strong/weak coupling model

    Jorge Casalderrey-Solana🇪🇸 · Guilherme Milhano🇵🇹 · Daniel Pablos🇺🇸 · Krishna Rajagopal🇺🇸

    We explore a set of jet substructure observables that use grooming techniques such as the Soft Drop procedure by performing simulations with the hybrid strong/weak coupling model for jet quenching. The results obtained for the observables presented in this proceedings, namely the number of Soft Drop splittings, or $n_{\mathrm{SD}}$, and the sharing momentum distribution $z_g$ for different angular cuts between the two main branches in a jet, can be easily understood as arising from the fact that among all the jets with a given jet $p_T$, those jets which are wider in opening angle, meaning that they have a higher jet mass and come from showers featuring more splittings, tend to lose more energy than the narrower jets. We comment on the comparison to data from ALICE and CMS, and point out the caveats arising from the consideration of smearing effects due to the presence of a large fluctuating background.

    hep-phPoS(2018)·2 citations
18. 18*

    Correlation between the decays $h^0\to \gamma \gamma /gg$ in the MSSM with quark flavour violation

    H. Eberl🇦🇹 · K. Hidaka🇯🇵 · E. Ginina🇦🇹

    We study the loop-induced decays $h^0\to \gamma \gamma$ and $h^0\to gg$ in the Minimal Supersymmetric Standard Model (MSSM) with quark flavour violation (QFV), identifying $h^0$ with the Higgs boson with a mass of 125 GeV, where $\gamma$ and $g$ are photon and gluon, respectively. We perform a MSSM parameter scan and a detailed analysis around a fixed reference point respecting theoretical constraints from vacuum stability conditions and experimental constraints, such as those from B meson data and electroweak precision data, as well as recent limits on supersymmetric (SUSY) particle masses from LHC experiments. We find that (i) the relative deviation of the decay width $\Gamma (h^0\to gg)$ from the Standard Model value, $DEV(g)$, can be large and negative, $\lesssim -15\%$, (ii) the analogous deviation of $\Gamma (h^0\to \gamma \gamma )$ is strongly correlated, $DEV(\gamma )\simeq -1/4DEV(g)$ for $DEV(g)\lesssim -4\%$, (iii) the relative deviation of the width ratio $\Gamma (h^0\to \gamma \gamma )/\Gamma (h^0\to gg)$ from the SM value, $DEV(\gamma /g)$, can be large (up to $\sim$ 20\%), (iv) the deviations can be large due to the up-type squark loop contributions, (v) the SUSY QFV parameters can have a significant effect on these deviations. Such large deviations can be observed at a future $e^{+}{e}^{-}$ collider like ILC. Observation of the deviation patterns as shown in this study would favour the MSSM with flavour-violating squark mixings and encourage to perform further studies in this model.

    hep-phInt.J.Mod.Phys.A(2019)·6 citations
19. 19*

    Higgsino Dark Matter in an economical Scherk-Schwarz setup

    Antonio Delgado🇺🇸 · Adam Martin🇺🇸 · Mariano Quiros🇪🇸

    We consider a minimal natural supersymmetric model based on an extra dimension with supersymmetry breaking provided by the Scherk-Schwarz mechanism. The lightest supersymmetric particle is a neutral, quasi-Dirac Higgsino and, unlike in previous studies, we assume that all Standard Model fields are propagating in the bulk. The resulting setup is minimal, as neither extra matter, effective operators, nor extra $U(1)$ groups are needed in order to be viable. The model has three free parameters which are fixed by the Higgsino mass -- set to the range 1.1-1.2 TeV so it can play the role of Dark Matter, and by the requirements of correct electroweak breaking and the mass of the Higgs. After imposing the previous conditions we find a benchmark scenario that passes all experimental constrains with an allowed range for the supersymmetric parameters. In particular we have found gluinos in the range 2.0-2.1 TeV mass, electroweakinos and sleptons almost degenerate in the range 1.7-1.9 TeV and squarks degenerate in the range 1.9-2.0 TeV. The best discovery prospects are: i.) gluino detection at the high luminosity LHC ($\gtrsim 3{\text{ab}}^{-1}$), and ii.) Higgsino detection at next-generation dark matter direct detection experiments. The model is natural, as the fine-tuning for the fixed values of the parameters is moderate mainly because supersymmetry breaking parameters contribute linearly to the Higgs mass parameter, rather than quadratically as in most models.

    hep-phPRD(2019)·4 citations
20. 20*

    Chiral Anomaly and Schwinger Effect in Non-Abelian Gauge Theories

    Valerie Domcke🇩🇪 · Yohei Ema🇩🇪 · Kyohei Mukaida🇩🇪 · Ryosuke Sato🇩🇪

    We study the production of chiral fermions in a background of a strong non-abelian gauge field with a non-vanishing Chern-Pontryagin density. We discuss both pair production analogous to the Schwinger effect as well as asymmetric production through the chiral anomaly, sourced by the Chern-Pontryagin density. In abelian gauge theories one may nicely understand these processes by considering that the fermion dispersion relation forms discrete Landau levels. Here we extend this analysis to a non-abelian gauge theory, considering an intrinsically non-abelian isotropic and homogeneous SU(2) gauge field background with a non-vanishing Chern-Pontryagin density. We show that the asymmetric fermion production, together with a non-trivial vacuum contribution, correctly reproduces the chiral anomaly. This indicates that the usual vacuum subtraction scheme, imposing normal ordering, fails in this case. As a concrete example of this gauge field background, we consider chromo-natural inflation. Applying our analysis to this particular model, we compute the backreaction of the generated fermions on the gauge field background. This backreaction receives contributions both from the vacuum through a Coleman-Weinberg-type correction and from the fermion excitations through an induced current.

    hep-phastro-ph.COcond-mat.mes-hallhep-thJHEP(2019)·35 citations
21. 21*

    Heavy neutral leptons and high-intensity observables

    Asmaa Abada🇫🇷 · Ana M. Teixeira🇫🇷

    New Physics models in which the Standard Model particle content is enlarged via the addition of sterile fermions remain among the most minimal and yet most appealing constructions, particularly since these states are present as building blocks of numerous mechanisms of neutrino mass generation. Should the new sterile states have non-negligible mixings to the active (light) neutrinos, and if they are not excessively heavy, one expects important contributions to numerous high-intensity observables, among them charged lepton flavour violating muon decays and transitions, and lepton electric dipole moments. We briefly review the prospects of these minimal SM extensions to several of the latter observables, considering both simple extensions and complete models of neutrino mass generation. We emphasise the existing synergy between different observables at the Intensity Frontier, which will be crucial in unveiling the new model at work.

    hep-phhep-exFront.in Phys.(2018)·32 citations
22. 22*

    Finite Quark-Mass Effects in Higgs Boson Production With Dijets at Large Energies

    Jeppe R. Andersen🇬🇧 · James D. Cockburn🇬🇧 · Marian Heil🇬🇧 · Andreas Maier🇩🇪 · Jennifer M. Smillie🇬🇧

    The production of a Higgs boson in association with at least two jets receives contributions both from the fusion of weak vector bosons (VBF) and from QCD processes, especially gluon fusion (GF). The former process is important for measuring the coupling of the Higgs boson to weak bosons, whereas the latter process plays an important role in determining any $CP$-admixtures in the Higgs sector. In this paper we go beyond the current state-of-the-art for fixed order calculations of the GF process (i.e. one loop $H+2j$ including full quark mass effects) by including the all-order effects in leading $\log (\hat{s}/p_t^2)$, together with full quark mass and loop-propagator kinematic effects. We calculate the mass-dependent components and implement the resummation within the framework of High Energy Jets. The high energy effects suppress the prediction compared to fixed order at large $\Delta y_{12}$ and $m_{jj}$ (and therefore within the usual VBF cuts of widely separated jets), just as found in the limit of $m_t\to \infty$. The mass dependence is more significant than at fixed order, because the systematic inclusion of the leading logarithms in $\hat{s}/p_t^2$ results in a hardening of the transverse momentum of the Higgs boson, which in turn probes in more detail the loop-structure of the coupling. In particular, the full mass dependence reduces the cross section within VBF cuts by 11\% compared to a calculation based just on the infinite top mass limit, but the impact of the bottom quark remains small. This all implies that the gluon-fusion contribution within VBF-cuts is less severe than current estimates suggest.

    hep-phJHEP(2019)·27 citations
23. 23*

    Lepton-jet Correlations in Deep Inelastic Scattering at the Electron-Ion Collider

    Xiaohui Liu🇨🇳 · Felix Ringer🇺🇸 · Werner Vogelsang🇩🇪 · Feng Yuan🇺🇸

    We propose the lepton-jet correlation in deep inelastic scattering as a unique tool for nucleon/nucleus tomography at the electron-ion collider. The azimuthal angular correlation between the final state lepton and jet depends on the transverse momentum dependent quark distributions. We take the example of single transverse spin asymmetries to show the sensitivity to the quark Sivers function. When the correlation is studied in lepton-nucleus collisions, transverse momentum broadening effects can be used to explore cold nuclear matter effects. These features make lepton-jet correlations an important new hard probe at the EIC.

    hep-phnucl-exnucl-thPRL(2019)·113 citations
24. 24*

    Uncertainties of hadronic scalar decay calculations

    F. Bezrukov🇬🇧 · D. Gorbunov🇷🇺 · I. Timiryasov🇨🇭

    Dispersion relations---a corollary of unitarity and analyticity---are among the few methods which can be employed to study low energy processes in QCD. In this work we critically revisit the calculation of decay widths of a hypothetical light scalar boson into pions and kaons. Strong interactions of the mesons in the final state affect these decays significantly. We argue that applications of the dispersion relations to the calculation of these decay widths, which are present in the literature, rely on an uncontrollable approximation of the reduced S-matrix. When a limited number of initial and final decay channels are considered, in general neither a unitary S-matrix nor its version corrected by an inelasticity factor are justified. The scalar form factor calculation provides a transparent example to illustrate this statement. Therefore, the results of this calculation, which are important for theoretical, cosmological and experimental applications, must be treated with caution. Our work, therefore, calls for a breakthrough in the understanding of the dispersion relations of realistic many-channel systems.

    hep-ph15 citations
25. 25*

    The "DIS and Related Subjects" Strategy Document: Fundamental Science from Lepton-Hadron Scattering

    Allen Caldwell🇩🇪 · Rolf Ent🇺🇸 · Aharon Levy🇮🇱 · Paul Newman🇬🇧 · Fred Olness🇺🇸

    The diverse community of scientists involved in Deep Inelastic Scattering includes about 2000 experimental and theoretical physicists worldwide and envisages projects such as the EIC, LHeC, FCC-eh and VHEeP as future lepton-hadron scattering facilities. The proposed facilities will address fundamental questions in strong interaction / QCD physics, including a first-ever tomographic mapping of the hadrons' internal structure, a solution to the proton mass and spin problems, understanding of the high-energy structure of hadronic matter and insight into connections between gravity and the strong interactions. They also extend and enhance the CERN programme of searches for new physics at the energy frontier, through a standalone precision Higgs and top programme, considerable sensitivity to the direct production of new particles and the most precise determinations of proton and nuclear structure in the kinematic range that is relevant to the LHC. In particular, we highlight the complementary aspects of the different lepton-hadron projects, and underscore how all are required to provide a complete characterization of the physics across the full kinematic reach. This review of the proposed facilities and their vast potential for particle physics was inspired by the discussions in the 2018 "DIS and Related Subjects" Workshop.

    hep-phhep-exnucl-ex7 citations
26. 26*

    Searching for dark matter in final states with two jets and missing transverse energy

    Ulrich Haisch🇩🇪 · Giacomo Polesello🇮🇹

    We reemphasise the usefulness of angular correlations in LHC searches for missing transverse energy ($E_T^{\mathrm{miss}}$) signatures that involve jet $(j)$ pairs with large invariant mass. For the case of mono-jet production via gluon-fusion, we develop a realistic analysis strategy that allows to split the dark matter (DM) signal into distinct one jet-like and two jet-like event samples. By performing state-of-the-art Monte Carlo simulations of both the mono-jet signature and the standard model background, it is shown that the dijet azimuthal angle difference $\Delta {\varphi }_{j_1{j}_2}$ in $2j+E_T^{\mathrm{miss}}$ production provides a powerful discriminant in realistic searches. Employing a shape fit to $\Delta {\varphi }_{j_1{j}_2}$, we then determine the LHC reach of the mono-jet channel in the context of spin-0 $s$-channel DM simplified models. The constraints obtained by the proposed $\Delta {\varphi }_{j_1{j}_2}$ shape fit turn out to be significantly more stringent than those that derive from standard $E_T^{\mathrm{miss}}$ shape analyses.

    hep-phhep-exJHEP(2019)·17 citations
27. 27*

    Machine learning classification: case of Higgs boson CP state in H to tau tau decay at LHC

    K. Lasocha🇵🇱 · E. Richter-Was🇵🇱 · D. Tracz🇵🇱 · Z. Was🇵🇱 · P. Winkowska🇵🇱

    Machine Learning (ML) techniques are rapidly finding a place among the methods of High Energy Physics data analysis. Different approaches are explored concerning how much effort should be put into building high-level variables based on physics insight into the problem, and when it is enough to rely on low-level ones, allowing ML methods to find patterns without explicit physics model. In this paper we continue the discussion of previous publications on the CP state of the Higgs boson measurement of the H to tau tau decay channel with the consecutive tau^pm to rho^pm nu; rho^pm to pi^pm pi^0 and tau^pm to a_1^pm nu; a_1^pm to rho^0 pi^pm to 3 pi^pm cascade decays. The discrimination of the Higgs boson CP state is studied as a binary classification problem between CP-even (scalar) and CP-odd (pseudoscalar), using Deep Neural Network (DNN). Improvements on the classification from the constraints on directly non-measurable outgoing neutrinos are discussed. We find, that once added, they enhance the sensitivity sizably, even if only imperfect information is provided. In addition to DNN we also evaluate and compare other ML methods: Boosted Trees (BT), Random Forest (RF) and Support Vector Machine (SVN).

    hep-phPRD(2019)·8 citations
28. 28*

    The CKM parameters in the SMEFT

    Sébastien Descotes-Genon🇫🇷 · Adam Falkowski🇫🇷 · Marco Fedele🇪🇸 · Martín González-Alonso🇨🇭 · Javier Virto🇩🇪

    The extraction of the Cabibbo-Kobayashi-Maskawa (CKM) matrix from flavour observables can be affected by physics beyond the Standard Model (SM). We provide a general roadmap to take this into account, which we apply to the case of the Standard Model Effective Field Theory (SMEFT). We choose a set of four input observables that determine the four Wolfenstein parameters, and discuss how the effects of dimension-six operators can be included in their definition. We provide numerical values and confidence intervals for the CKM parameters, and compare them with the results of CKM fits obtained in the SM context. Our approach allows one to perform general SMEFT analyses in a consistent fashion, independently of any assumptions about the way new physics affects flavour observables. We discuss a few examples illustrating how our approach can be implemented in practice.

    hep-phhep-exJHEP(2019)·82 citations
29. 29*

    PHOTON-2017 conference proceedings

    David d'Enterria · Albert de Roeck · Michelangelo Mangano (eds.) · Jaroslav Adam · Massimiliano Alvioli · Christopher D. Anson · Hamed Bakhshiansohi · Cristian Baldenegro · Valerio Bertone · Stanley J. Brodsky · Peter J. Bussey · Chav Chhiv Chau and 69 other authors

    This document collects the proceedings of the PHOTON 2017 conference ("International Conference on the Structure and the Interactions of the Photon", including the 22th "International Workshop on Photon-Photon Collisions", and the "International Workshop on High Energy Photon Colliders") held at CERN (Geneva) in May 2017. The latest experimental and theoretical developments on the topics of the PHOTON conference series are covered: (i) $\gamma \gamma$ processes in e${}^{+}$e${}^{-}$, proton-proton (pp) and nucleus-nucleus (AA) collisions at current and future colliders, (ii) $\gamma$-hadron interactions in e${}^{\pm }$p, pp, and AA collisions, (iii) final-state photon production (including Standard Model studies and searches beyond it) in pp and AA collisions, and (iv) high-energy $\gamma$-ray astrophysics. These proceedings are dedicated to the memory of Maria Krawczyk.

    hep-phhep-exnucl-exnucl-thCERN Proc.(2018)·6 citations
30. 30*

    Discovering the Twin Higgs Boson with Displaced Decays

    Can Kilic🇺🇸 · Saereh Najjari🇧🇪 · Christopher B. Verhaaren🇺🇸

    The Twin Higgs mechanism keeps the scalar sector of the Standard Model (SM) natural while remaining consistent with the non-observation of new colored particles at the Large Hadron Collider (LHC). In this construction the heavy twin Higgs boson provides a portal between the SM particles and the twin sector, but is quite challenging to discover at colliders. In the Fraternal Twin Higgs setup, where light twin quarks are absent, we study a novel discovery channel for the heavy twin Higgs boson by considering its decay to a pair of light Higgs bosons, one of which subsequently decays to glueball states in the twin sector, leading to displaced vertex signatures. We estimate the sensitivity of existing LHC searches in this channel, and assess the discovery potential of the high luminosity (HL) LHC. We show that the glueballs probed by these searches are outside the sensitivity of existing searches for exotic decays of the light Higgs boson. In addition, we demonstrate that the displaced signals we consider probe a region of heavy Higgs masses beyond the reach of prompt signals. We also comment on the possibility of probing the input parameters of the microscopic physics and providing a way to test the Twin Higgs mechanism with this channel.

    hep-phhep-exPRD(2019)·34 citations
31. 31*

    Automatic Peccei-Quinn symmetry

    M.B. Gavela🇪🇸 · M. Ibe🇯🇵 · P. Quilez🇪🇸 · T. T. Yanagida🇯🇵

    We present a dynamical (composite) axion model where the Peccei-Quinn (PQ) symmetry arises automatically as a consequence of chirality and gauge symmetry. The Standard Model is simply extended by a confining and chiral $SU(5)$ gauge symmetry. The PQ symmetry coincides with a $B-L$ symmetry of the exotic sector. The theory is protected by construction from quantum gravitational corrections stemming from operators with mass dimension lower than nine.

    hep-phEPJC(2019)·71 citations
32. 32*

    Cosmic neutrino background search experiments as decaying dark matter detectors

    David McKeen🇨🇦

    We investigate the possibility that particles that are long-lived on cosmological scales, making up part or all of the dark matter, decay to neutrinos that have present-day energies around an eV. The neutrinos from these decays can potentially be visible at experiments that hope to directly observe the cosmic neutrino background through neutrino capture on tritium, such as PTOLEMY. In the context of a simple model that can realize such decays, we discuss the allowed signatures at a PTOLEMY-like experiment given current cosmological constraints.

    hep-phastro-ph.COhep-exPRD(2019)·38 citations
33. 33*

    Almost Inert Higgs Bosons at the LHC

    Christina Gao🇺🇸 · Markus A. Luty🇺🇸 · Nicolás A. Neill🇨🇱

    Non-minimal Higgs sectors are strongly constrained by the agreement of the measured couplings of the 125 GeV Higgs with Standard Model predictions. This agreement can be explained by an approximate ${\mathbb{Z}}_2$ symmetry under which the additional Higgs bosons are odd. This allows the additional Higgs bosons to be approximately inert, meaning that they have suppressed VEVs and suppressed mixing with the Standard Model Higgs. In this case, single production of the new Higgs bosons is suppressed, but electroweak pair production is unsuppressed. We study the phenomenology of a minimal 2 Higgs doublet model that realizes this scenario. In a wide range of parameters, the phenomenology of the model is essentially fixed by the masses of the exotic Higgs bosons, and can therefore be explored systematically. We study a number of different plausible signals in this model, and show that several LHC searches can constrain or discover additional Higgs bosons in this parameter space. We find that the reach is significantly extended at the high luminosity LHC.

    hep-phJHEP(2019)·6 citations
34. 34*

    Symmetry Breaking and Reheating after Inflation in No-Scale Flipped SU(5)

    John Ellis🇬🇧 · Marcos A. G. Garcia🇺🇸 · Natsumi Nagata🇯🇵 · Dimitri V. Nanopoulos🇺🇸 · Keith A. Olive🇺🇸

    No-scale supergravity and the flipped SU(5)$\times$U(1) gauge group provide an ambitious prototype string-inspired scenario for physics below the string scale, which can accommodate the Starobinsky-like inflation favoured by observation when the inflaton is associated with one of the singlet fields associated with neutrino mass generation. During inflation, the vacuum remains in the unbroken GUT phase, and GUT symmetry breaking occurs later when a field with a flat direction (the flaton) acquires a vacuum expectation value. Inflaton decay and the reheating process depend crucially on GUT symmetry breaking, as decay channels open and close, depending on the value of the flaton vacuum expectation value. Here, we consider the simultaneous cosmological evolution of both the inflaton and flaton fields after inflation. We distinguish weak, moderate and strong reheating regimes, and calculate in each case the entropy produced as all fields settle to their global minima. These three reheating scenarios differ in the value of a Yukawa coupling that introduces mass mixing between the singlets and the $10$s of SU(5). The dynamics of the GUT transition has an important impact on the production of gravitinos, and we also discuss the pattern of neutrino masses we expect in each of the three cases. Finally, we use recent CMB limits on neutrino masses to constrain the reheating models, finding that neutrino masses and the cosmological baryon asymmetry can both be explained if the reheating is strong.

    hep-phastro-ph.COgr-qchep-thJCAP(2019)·34 citations
35. 35*

    Subleading Power Rapidity Divergences and Power Corrections for $q_T$

    Markus A. Ebert🇺🇸 · Ian Moult🇺🇸 · Iain W. Stewart🇺🇸 · Frank J. Tackmann🇩🇪 · Gherardo Vita🇺🇸 · Hua Xing Zhu🇨🇳

    A number of important observables exhibit logarithms in their perturbative description that are induced by emissions at widely separated rapidities. These include transverse-momentum ($q_T$) logarithms, logarithms involving heavy-quark or electroweak gauge boson masses, and small-$x$ logarithms. In this paper, we initiate the study of rapidity logarithms, and the associated rapidity divergences, at subleading order in the power expansion. This is accomplished using the soft collinear effective theory (SCET). We discuss the structure of subleading-power rapidity divergences and how to consistently regulate them. We introduce a new pure rapidity regulator and a corresponding $\overline{\mathrm{MS}}$-like scheme, which handles rapidity divergences while maintaining the homogeneity of the power expansion. We find that power-law rapidity divergences appear at subleading power, which give rise to derivatives of parton distribution functions. As a concrete example, we consider the $q_T$ spectrum for color-singlet production, for which we compute the complete $q_T^2/Q^2$ suppressed power corrections at $\mathcal{O}({\alpha }_s)$, including both logarithmic and nonlogarithmic terms. Our results also represent an important first step towards carrying out a resummation of subleading-power rapidity logarithms.

    hep-phnucl-thJHEP(2019)·163 citations
36. 36*

    ${\alpha }_s(\mu )$ from $M_{{\chi }_{0c(0b)}}-M_{{\eta }_{c(b)}}$@N2LO

    Stephan Narison (LUPM-CNRS/IN2P3, Montpellier-FR)🇫🇷

    This note complements and clarifies the results obtained in the original paper {\it QCD Parameters Correlations from Heavy Quarkonia} [1] where, here, we present a more detailed discussion of the \alpha_s-results obtained @ N2LO at two different subtraction scales \mu=2.85 and 9.50 GeV from the (pseudo)scalar heavy quarkonia mass-spliitings M_{\chi_{0c(0b)}}-M_{\eta_{c(b)}}. We obtain from the M_{\chi_{0c}}-M_{\eta_{c}} sum rule: \alpha_s(2.85)=0.262(9) --> \alpha_s(M_\tau)=0.318(15) --> \alpha_s(M_Z)=0.1183(19)(3) and from the M_{\chi_{0b}}-M_{\eta_{b}} one: \alpha_s(9.50)=0.180(8) --> \alpha_s(M_\tau)=0.312(27) --> \alpha_s(M_Z)=0.1175(32)(3), in complete agreement with the world average: \alpha_s(M_Z)=0.1181(11).

    hep-phhep-exhep-lat17 citations
37. 37*

    Exotic compact objects with soft hair

    Guilherme Raposo🇮🇹 · Paolo Pani🇮🇹 · Roberto Emparan🇪🇸

    Motivated by the lack of a general parametrization for exotic compact objects, we construct a class of perturbative solutions valid for small (but otherwise generic) multipolar deviations from a Schwarzschild metric in general relativity. We introduce two classes of exotic compact objects, with "soft" and "hard" hair, for which the curvature at the surface is respectively comparable to or much larger than that at the corresponding black-hole horizon. We extend the Hartle-Thorne formalism to relax the assumption of equatorial symmetry and to include deformations induced by multipole moments higher than the spin, thus constructing the most general, axisymmetric quasi-Schwarzschild solution to Einstein's vacuum equations. We explicitly construct several particular solutions of objects with soft hair, which might be useful for tests of quasi-black-hole metrics, and also to study deformed neutron stars. We show that the more compact a soft exotic object is, the less hairy it will be. All its multipole moments can approach their corresponding Kerr values only in two ways as their compactness increases: either logarithmically (or faster) if the moments are spin-induced, or linearly (or faster) otherwise. Our results suggest that it is challenging (but possibly feasible with next-generation gravitational-wave detectors) to distinguish Kerr black holes from a large class of ultracompact exotic objects on the basis of their different multipolar structure.

    ↳ gr-qcastro-ph.HEhep-phhep-thPRD(2019)·74 citations
38. 38*

    de Sitter swampland bound in the Dirac-Born-Infeld inflation model

    Min-Seok Seo🇰🇷

    We study the de Sitter (dS) swampland conjecture in the Dirac-Born-Infeld (DBI) inflation model. We obtain the dS swampland bound for the relativistic regime using Bousso's entropy bound argument and proper distance. It restricts $m_{\mathrm{Pl}}\nabla V/V$ by some positive constant depending on warping and the field range. In the specific case of the DBI model driven by the quadratic potential, the model-dependent backreaction argument is interpreted as a natural bound for the slow-roll parameter. This shows that quasi-dS spacetime in the DBI model is a result of tuning.

    ↳ hep-thastro-ph.COhep-phPRD(2019)·30 citations
39. 39*

    Electromagnetic currents for dressed hadrons

    Helmut Haberzettl🇺🇸

    We propose an extension of the minimal-substitution prescription for coupling the electromagnetic field to hadronic systems with internal structure. The resulting rules of extended substitution necessarily distinguish between couplings to scalar and Dirac particles. Moreover, they allow for the incorporation of electromagnetic form factors for virtual photons in an effective phenomenological framework. Applied to pions and nucleons, assumed to be fully dressed to all orders, the resulting dressed currents are shown to be locally gauge invariant. Moreover, half-on-shell expressions of (hadron propagator)$\times$(electromagnetic current) needed in all descriptions of physical processes will lose \textit{all} information about hadronic dressing for real photons. The Ball-Chiu ansatz for the spin-1/2 current is seen to suffer from an incomplete coupling procedure where some essential aspects of the Dirac particle are effectively treated as those of a scalar particle. Applied to real Compton scattering on pions and nucleons, we find that \emph{all} dressing information cancels exactly when external hadrons are on shell, leaving only gauge-invariant bare Born-type contributions with physical masses. Hence, nontrivial descriptions necessarily require contact-type two-photon processes obtained by hadrons looping around two photon insertion points.

    ↳ nucl-thhep-phPRD(2019)·3 citations
40. 40*

    COMET - A submission to the 2020 update of the European Strategy for Particle Physics on behalf of the COMET collaboration

    J.-C. Angélique🇫🇷 · C. Cârloganu🇫🇷 · W. da Silva🇫🇷 · A. Drutskoy🇷🇺 · M. Finger🇨🇿 · D. N. Grigoriev🇷🇺 · T. Kachelhoffer🇫🇷 · F. Kapusta🇫🇷 · Y. Kuno🇯🇵 · P. Lebrun🇺🇸 · R. P. Litchfield🇬🇧 · D. Lomidze🇬🇪 and 7 other authors

    The search for charged lepton flavour violation (CLFV) has enormous discovery potential in probing new physics Beyond the Standard Model (BSM). Among the muonic CLFV processes, $\mu \to e$ conversion is one of the most important processes, having several advantages compared to other such processes. We describe the COMET experiment, which is searching for $\mu \to e$ conversion in a muonic atom at the J-PARC proton accelerator laboratory in Japan. The COMET experiment has taken a staged approach; the first stage, COMET Phase-I, is currently under construction at J-PARC, and is aiming at a factor 100 improvement over the current limit. The second stage, COMET Phase-II is seeking another 100 improvement (a total of 10,000), allowing a single event sensitivity (SES) of $2.6\times 10^{-17}$ with $2\times 10^7$ seconds of data-taking. Further improvements by one order of magnitude, which arise from refinements to the experimental design and operation, are being considered whilst staying within the originally-assumed beam power and beam time. Such a sensitivity could be translated into probing many new physics constructions up to $\mathcal{O}(10^4)$ TeV energy scales, which would go far beyond the level that can be reached directly by collider experiments. The search for CLFV $\mu \to e$ conversion is thus highly complementary to BSM searches at the LHC.

    ↳ hep-exhep-ph23 citations
41. 41*

    Hidden and explicit quantum scale invariance

    Sander Mooij🇨🇭 · Mikhail Shaposhnikov🇨🇭 · Thibault Voumard🇨🇭

    There exist renormalisation schemes that explicitly preserve the scale invariance of a theory at the quantum level. Imposing a scale invariant renormalisation breaks renormalisability and induces new non-trivial operators in the theory. In this work, we study the effects of such scale invariant renormalisation procedures. On the one hand, an explicitly quantum scale invariant theory can emerge from the scale invariant renormalisation of a scale invariant Lagrangian. On the other hand, we show how a quantum scale invariant theory can equally emerge from a Lagrangian visibly breaking scale invariance renormalised with scale dependent renormalisation (such as the traditional MS-bar scheme). In this last case, scale invariance is hidden in the theory, in the sense that it only appears explicitly after renormalisation.

    ↳ hep-thhep-phPRD(2019)·29 citations
42. 42*

    Searches for Higgs bosons with dark matter at the Large Hadron Collider

    Michele Gallinaro (on behalf of the ATLAS and CMS collaborations)🇵🇹

    Convincing and direct evidence for dark matter (DM) on galactic scales comes from the observation of the rotation curves of galaxies. At particle colliders, searches for DM involve the production of a pair of stable electrically neutral and weakly interacting particles with a signature of missing transverse energy ($E_{\mathrm{miss}}^{\mathrm{T}}$) recoiling against a SM particle. The resulting signature yields a final state denoted as X+$E_{\mathrm{miss}}^{\mathrm{T}}$, where the SM particle X is emitted as initial state radiation. The Higgs boson discovery at the LHC opens a new window into the searches for new physics processes beyond the SM through the h+$E_{\mathrm{miss}}^{\mathrm{T}}$ signature, as a direct probe of the interaction involving DM particles. Due to the small Yukawa couplings to quarks and gluons, the initial state radiation of the Higgs boson is suppressed, but it can be produced in the case of a new interaction with DM particles. Searches for DM particles produced in association with the Higgs boson are discussed. They are based on proton-proton collision data at the LHC in different final states.

    ↳ hep-exhep-phPoS(2019)·0 citations
43. 43*

    Multi-wavelength astronomical searches for primordial black holes

    Julien Manshanden🇳🇱 · Daniele Gaggero🇳🇱 · Gianfranco Bertone🇳🇱 · Riley M. T. Connors🇳🇱 · Massimo Ricotti🇺🇸

    If primordial black holes of $\mathcal{O}(1-100)M_{\odot }$ constitute a significant portion of the dark matter in the Universe, they should be very abundant in our Galaxy. We present here a detailed analysis of the radio and X-ray emission that these objects are expected to produce due to the accretion of gas from the interstellar medium. With respect to previous studies, we relax the assumption of a monochromatic mass function, and introduce an improved treatment of the physics of gas accretion onto isolated, moving compact objects, based on a set of state-of-the-art numerical simulations. By comparing our predictions with known radio and X-ray sources in the Galactic center region, we show that the maximum relic density of primordial black holes in the mass range of interest is $\sim 10^{-3}$ smaller than that of dark matter. The new upper bound is two orders of magnitude stronger with respect to previous results, based on a conservative phenomenological treatment of the accretion physics. We also provide a comprehensive critical discussion on the reliability of this bound, and on possible future developments in the field. We argue in particular that future multi-wavelength searches will soon start to probe the galactic population of astrophysical black holes.

    ↳ astro-ph.HEhep-phJCAP(2019)·87 citations
44. 44*

    The Compact Linear e${}^{+}$e${}^{-}$ Collider (CLIC): Physics Potential

    P. Roloff🇨🇭 · R. Franceschini🇮🇹 · U. Schnoor🇨🇭 · A. Wulzer🇨🇭

    The Compact Linear Collider, CLIC, is a proposed e${}^{+}$e${}^{-}$ collider at the TeV scale whose physics potential ranges from high-precision measurements to extensive direct sensitivity to physics beyond the Standard Model. This document summarises the physics potential of CLIC, obtained in detailed studies, many based on full simulation of the CLIC detector. CLIC covers one order of magnitude of centre-of-mass energies from 350 GeV to 3 TeV, giving access to large event samples for a variety of SM processes, many of them for the first time in e${}^{+}$e${}^{-}$ collisions or for the first time at all. The high collision energy combined with the large luminosity and clean environment of the e${}^{+}$e${}^{-}$ collisions enables the measurement of the properties of Standard Model particles, such as the Higgs boson and the top quark, with unparalleled precision. CLIC might also discover indirect effects of very heavy new physics by probing the parameters of the Standard Model Effective Field Theory with an unprecedented level of precision. The direct and indirect reach of CLIC to physics beyond the Standard Model significantly exceeds that of the HL-LHC. This includes new particles detected in challenging non-standard signatures. With this physics programme, CLIC will decisively advance our knowledge relating to the open questions of particle physics.

    ↳ hep-exhep-ph122 citations
45. 45*

    Semi-inclusive jets recoiling from ${\gamma }_{dir}$ and ${\pi }^0$ triggers in central Au+Au collisions at $\sqrt{s_{\mathrm{NN}}}$ = 200 GeV in STAR

    Nihar Ranjan Sahoo (For the STAR Collaboration)🇺🇸

    We report the first measurement of fully corrected semi-inclusive charged recoil jets for both direct-photon (${\gamma }_{dir}$) and ${\pi }^0$ triggers, within two trigger transverse energy ranges between 9 GeV and 15 GeV, in central Au+Au collisions at $\sqrt{s_{\mathrm{NN}}}$ = 200 GeV using data with an integrated luminosity of 13 $\mathrm{n}{\mathrm{b}}^{-1}$ collected by the STAR experiment. A comparison between ${\pi }^0$-triggered recoil jets in p+p collisions and PYTHIA is discussed. A comparison is also presented between the suppression of ${\gamma }_{dir}$- and ${\pi }^0$-triggered recoil jets in central Au+Au collisions with respect to their corresponding PYTHIA references. A strong and similar level of suppression is observed in recoil-jet yields as a function of jet transverse momentum for ${\gamma }_{dir}$+jet and ${\pi }^0$+jet.

    ↳ nucl-exhep-exhep-phnucl-thPoS(2018)·1 citation
46. 46*

    Direct photon production and flow at low transverse momenta in pp, p-Pb and Pb-Pb collisions

    Nicolas Schmidt (for the ALICE Collaboration)🇺🇸

    Low transverse momentum direct photon measurements have been carried out by the ALICE experiment at the CERN LHC in small collision systems (pp, $\sqrt{s}=2.76$ and 8 TeV and p--Pb, $\sqrt{s_{\text{NN}}}=5.02$ TeV) as well as in heavy-ion collisions (Pb--Pb, $\sqrt{s_{\text{NN}}}=2.76$ TeV). For the first time, also the multiplicity dependence of direct photon production was investigated in p--Pb collisions. Whereas in the small systems no significant thermal photon signal was observed, a $\sim 15\%$ excess has been measured in central Pb--Pb collisions in the region of $p_{\mathrm{T}}<3$ GeV/$c$. A signal of prompt photon production at high transverse momentum consistent with binary scaling has been observed in all collision systems following NLO pQCD predictions. Direct photon flow has been measured in central and semi-central Pb--Pb collisions and found to be of similar size as the charged hadron and decay photon flow.

    ↳ nucl-exhep-exhep-phnucl-thPoS(2018)·7 citations
47. 47*

    Entanglement and thermalization

    Jürgen Berges🇩🇪 · Stefan Floerchinger🇩🇪 · Raju Venugopalan🇺🇸

    In a quantum field theory, apparent thermalization can be a consequence of entanglement as opposed to scatterings. We discuss here how this can help to explain open puzzles such as the success of thermal models in electron-positron collisions. It turns out that an expanding relativistic string described by the Schwinger model (which also underlies the Lund model) has at early times an entanglement entropy that is extensive in rapidity. At these early times, the reduced density operator is of thermal form, with an entanglement temperature $T_{\tau }=\hslash /(2\pi k_B\tau )$, even in the absence of any scatterings.

    ↳ hep-thhep-phNPA(2019)·18 citations
48. 48*

    Physics perspectives with heavy ions in the HL-LHC phase and beyond

    Stefan Floerchinger🇩🇪

    The current state of research on high-energy heavy ion physics, including its motivations and purpose is reviewed from a theorist's perspective. Possible future directions are discussed, in particular the possibility of investigating the regime of small transverse momenta in more detail and an improved interplay between experiments and dedicated theory development.

    ↳ nucl-thhep-phPoS(2018)·0 citations
49. 49*

    Study in the noncanonical domain of Goldstone inflation

    Sukannya Bhattacharya🇮🇳 · Mayukh R. Gangopadhyay🇮🇳

    Recent observations of the cosmic microwave background (CMB) indicate that a successful theory of cosmological inflation needs to have flat potential of the inflaton scalar field. Realizing the inflaton to be a pseudo-Nambu Goldstone boson (pNGB) could ensure the flatness and the sub-Planckian scales related to the dynamics of the paradigm. In this work, we have taken the most general form of such a scenario: Goldstone inflation, and studied the model in the noncanonical domain. Natural inflation is a limiting case of this model, which is also studied here in the noncanonical regime. Our result is compared with the recent release by Planck collaboration and it is shown that for some combination of the model parameters, a Goldstone inflationary model in the noncanonical realisation obeys the current observational bounds. Then, we studied the era of reheating after the end of inflation. For different choice of model parameters, constraints on the reheating temperature ($T_{\mathrm{re}}$) and number of e-folds during reheating($N_{\mathrm{re}}$) for the allowed inflationary observables (e.g. scalar spectral index($n_s$) and tensor to scalar ratio($r$)) are predicted for this model.

    ↳ astro-ph.COhep-phPRD(2020)·13 citations
50. 50*

    Angular and CP-violation analyses of $\bar{B}\to D^{\ast +}{l}^{-}{\bar{\nu }}_l$ decays at hadron collider experiments

    Daniele Marangotto🇮🇹

    The $\bar{B}\to D^{\ast +}{l}^{-}{\bar{\nu }}_l$ branching fraction ratio $R(D^{\ast })$ has shown intriguing discrepancies between the Standard Model prediction and measurements performed at BaBar, Belle and LHCb experiments, a possible sign of beyond the Standard Model physics. Theoretical studies prove how observables related to the $\bar{B}\to D^{\ast +}{l}^{-}{\bar{\nu }}_l$ differential decay distribution can be used to further constrain New Physics contributions, but their experimental measurements is lacking to date. This article presents the attainable precision on the measurement of $\bar{B}\to D^{\ast +}{l}^{-}{\bar{\nu }}_l$ angular and CP-violating observables by exploiting approximate reconstruction algorithms using information from detectable final-state particles only, a case of special interest for hadron collider experiments. The resolution on the phase space variables is studied using $\bar{B}\to D^{\ast +}{l}^{-}{\bar{\nu }}_l$ decays simulated in a forward detector geometry like LHCb. A novel method to correct the observable values for the reconstruction inaccuracies based on detector simulation is successfully tested on simulated data and the decrease in precision with respect to a perfect reconstruction is evaluated. The $D^{\ast +}$ longitudinal polarization fraction and one of the CP-violating observables can be measured losing a factor 2 and 5 in precision, respectively. The extraction of phase space distributions from the template fit selecting $\bar{B}\to D^{\ast +}{l}^{-}{\bar{\nu }}_l$ decays and associated systematic uncertainties are also discussed.

    ↳ hep-exhep-phAdv.High Energy Phys.(2019)·5 citations
51. 51*

    Testing Dark Matter and Modifications to Gravity using Local Milky Way Observables

    Mariangela Lisanti🇺🇸 · Matthew Moschella🇺🇸 · Nadav Joseph Outmezguine🇮🇱 · Oren Slone🇺🇸

    Galactic rotation curves are often considered the first robust evidence for the existence of dark matter. However, even in the presence of a dark matter halo, other galactic-scale observations, such as the Baryonic Tully-Fisher Relation and the Radial Acceleration Relation, remain challenging to explain. This has motivated long-distance, infrared modifications to gravity as an alternative to the dark matter hypothesis as well as various DM theories with similar phenomenology. In general, the standard lore has been that any model that reduces to the phenomenology of MOdified Newtonian Dynamics (MOND) on galactic scales explains essentially all galaxy-scale observables. We present a framework to test precisely this statement using local Milky Way observables, including the vertical acceleration field, the rotation curve, the baryonic surface density, and the stellar disk profile. We focus on models that predict scalar amplifications of gravity, i.e., models that increase the magnitude but do not change the direction of the gravitational acceleration. We find that models of this type are disfavored relative to a simple dark matter halo model because the Milky Way data requires a substantial amplification of the radial acceleration with little amplification of the vertical acceleration. We conclude that models which result in a MOND-like force struggle to simultaneously explain both the rotational velocity and vertical motion of nearby stars in the Milky Way.

    ↳ astro-ph.GAastro-ph.COhep-phPRD(2019)·37 citations
52. 52*

    Discrete Gauge Symmetries and the Weak Gravity Conjecture

    Nathaniel Craig🇺🇸 · Isabel Garcia Garcia🇺🇸 · Seth Koren🇺🇸

    In theories with discrete Abelian gauge groups, requiring that black holes be able to lose their charge as they evaporate leads to an upper bound on the product of a charged particle's mass and the cutoff scale above which the effective description of the theory breaks down. This suggests that a non-trivial version of the Weak Gravity Conjecture (WGC) may also apply to gauge symmetries that are discrete, despite there being no associated massless field, therefore pushing the conjecture beyond the slogan that `gravity is the weakest force'. Here, we take a step towards making this expectation more precise by studying ${\mathbb{Z}}_N$ and ${\mathbb{Z}}_2^N$ gauge symmetries realised via theories of spontaneous symmetry breaking. We show that applying the WGC to a dual description of an Abelian Higgs model leads to constraints that allow us to saturate but not violate existing bounds on discrete symmetries based on black hole arguments. In this setting, considering the effect of discrete hair on black holes naturally identifies the cutoff of the effective theory with the scale of spontaneous symmetry breaking, and provides a mechanism through which discrete hair can be lost without modifying the gravitational sector. We explore the possible implications of these arguments for understanding the smallness of the weak scale compared to $M_{Pl}$.

    ↳ hep-thgr-qchep-phJHEP(2019)·30 citations
53. 53*

    Event-shape engineering and heavy-flavour observables in relativistic heavy-ion collisions

    A. Beraudo🇮🇹 · A. De Pace🇮🇹 · M. Monteno🇮🇹 · M. Nardi🇮🇹 · F. Prino🇮🇹

    Traditionally, events collected at relativistic heavy-ion colliders are classified according to some centrality estimator (e.g. the number of produced charged particles) related to the initial energy density and volume of the system. In a naive picture the latter are directly related to the impact parameter of the two nuclei, which sets also the initial eccentricity of the system: zero in the case of the most central events and getting larger for more peripheral collisions. A more realistic modelling requires to take into account event-by-event fluctuations, in particular in the nucleon positions within the colliding nuclei: collisions belonging to the same centrality class can give rise to systems with different initial eccentricity and hence different flow harmonics for the final hadron distributions. This issue can be addressed by an event-shape-engineering analysis, consisting in selecting events with the same centrality but different magnitude of the average bulk anisotropic flow and therefore of the initial-state eccentricity. In this paper we present the implementation of this analysis in the POWLANG transport model, providing predictions for the transverse-momentum and angular distributions of charm and beauty hadrons for event-shape selected collisions. In this way it is possible to get information on how the heavy quarks propagating (and hadronizing) in a hot environment respond both to its energy density and to its geometric asymmetry, breaking the perfect correlation between eccentricity and impact parameter which characterizes a modelling of the medium based on smooth average initial conditions

    ↳ physics.data-anhep-phnucl-exnucl-thEPJC(2019)·20 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.