Wed·Jan 29, 2020Wednesday·January 29, 2020

1. 01*

   Event Generation with Normalizing Flows

   Christina Gao🇺🇸 · Stefan Hoeche🇺🇸 · Joshua Isaacson🇺🇸 · Claudius Krause🇺🇸 · Holger Schulz🇺🇸

   We present a novel integrator based on normalizing flows which can be used to improve the unweighting efficiency of Monte-Carlo event generators for collider physics simulations. In contrast to machine learning approaches based on surrogate models, our method generates the correct result even if the underlying neural networks are not optimally trained. We exemplify the new strategy using the example of Drell-Yan type processes at the LHC, both at leading and partially at next-to-leading order QCD.

   hep-phPRD(2020)·175 citations
2. 02*

   Hard probes of non-equilibrium quark-gluon plasma

   Sigtryggur Hauksson🇨🇦 · Sangyong Jeon🇨🇦 · Charles Gale🇨🇦

   Jets and photons could play an important role in finding the transport coefficients of the quark-gluon plasma. To this end we analyze their interaction with a non-equilibrium quark-gluon plasma. Using new field-theoretical tools we derive two-point correlators for the plasma which show how instabilities evolve in time. This allows us, for the first time, to derive finite rates of interaction with the medium. We furthermore show that coherent, long-wavelength instability fields in the Abelian limit do not modify the rate of photon emission or jet-medium interaction.

   hep-phnucl-thNPA(2021)·5 citations
3. 03*

   The gallium anomaly reassessed using a Bayesian approach

   Joel Kostensalo🇫🇮 · Santtu Tikka🇫🇮 · Jouni Suhonen🇫🇮

   The solar-neutrino detectors GALLEX and SAGE were calibrated by electron-neutrino flux from the ${}^{37}$Ar and ${}^{51}$Cr calibration sources. A deficit in the measured neutrino flux was recorded by counting the number of neutrino-induced conversions of the ${}^{71}$Ga nuclei to ${}^{71}$Ge nuclei. This deficit was coined ``gallium anomaly'' and it has lead to speculations about beyond-the-standard-model physics in the form of eV-mass sterile neutrinos. Notably, this anomaly has already defied final solution for more than 20 years. Here we reassess the statistical significance of this anomaly and improve the related statistical approaches by treating the neutrino experiments as repeated Bernoulli trials taking into account the fact that the number of the detected ${}^{71}$Ge nuclei is quite small, thus calling for a Bayesian statistical approach. In addition, we take into account the systematic errors of the experiments, their correlations, theoretical uncertainties and the number of background solar-neutrino events as a Poisson-distributed random variable. To compare with the previously reported statistical significances of the anomaly we convert the posterior intervals of our Bayesian approach to standard deviations $\sigma$ of the frequentist approach. We find that our approach reduces the statistical significance of the anomaly by $0.8\sigma$ for all the adopted theoretical approaches. This renders the gallium anomaly a statistically weakly supported concept. Furthermore, the implications of our approach go far beyond the gallium anomaly since the results of many rare-events experiments should be reassessed for their limited number of recorded events.

   hep-ph6 citations
4. 04*

   Semileptonic Decays of Charmed Mesons to Light Scalar Mesons

   Nakul R. Soni🇮🇳 · Akshay N. Gadaria🇮🇳 · Janaki J. Patel🇮🇳 · Jignesh N. Pandya🇮🇳

   Within the framework of covariant confined quark model, we compute the transition form factors of $D$ and $D_s$ mesons decaying to light scalar mesons $f_0(980)$ and $a_0(980)$. The transition form factors are then utilized to compute the semileptonic branching fractions. We study the channels namely, $D_{(s)}^{+}\to f_0(980){\ell }^{+}{\nu }_{\ell }$ and $D\to a_0(980){\ell }^{+}{\nu }_{\ell }$ for $\ell =e$ and $\mu$. For computation of semileptonic branching fractions, we consider the $a_0(980)$ meson to be the conventional quark-antiquark structure and the $f_0(980)$ meson as the admixture of $s\bar{s}$ and light quark-antiquark pairs. Our findings are found to support the recent BESIII data.

   hep-phPRD(2020)·42 citations
5. 05*

   Photon induced K$\Lambda$ production on the proton in the low energy region

   A. Fatima🇮🇳 · Z. Ahmad Dar🇮🇳 · M. Sajjad Athar🇮🇳 · S. K. Singh🇮🇳

   The associated photoproduction of $K\Lambda$ from the proton in the low energy region is studied using an isobar model in which the non-resonant contributions are obtained from the non-linear sigma model with chiral SU(3) symmetry which predicts, in a natural way, the contact term with its coupling strength along with the coupling strengths of the various Born terms predicted by the non-linear sigma model. The present model is an extension of the non-linear sigma model with chiral SU(2) symmetry, used earlier to study the photo, electro, and neutrino productions of pions. In the resonance sector, the contributions from the well established nucleon resonances ($R$) in the $s$ channel, the hyperon resonances ($Y^{\ast }$) in the $u$ channel, and the kaon resonances ($K^{\ast }$ and $K_1$) in the $t$ channel having spin $\le \frac{3}{2}$ and mass $<2$ GeV with a significant branching ratio in $K\Lambda$ decay mode, have been considered. The strong and electromagnetic couplings of the $s$ channel nucleon resonances are taken from experiments while the couplings for the resonances in the $t$ and $u$ channels are fitted to reproduce the current data on the associated photoproduction of $K\Lambda$ in this energy region. The numerical results are presented for the total and differential cross sections and are compared with the available experimental data from CLAS and SAPHIR as well as with some of the recent theoretical models.

   hep-phnucl-thIJMPE(2020)·12 citations
6. 06*

   Comment on "Heavy Quarkonium in Extreme Conditions"

   Masayuki Asakawa🇯🇵

   In a recent paper (arXiv:1912.02253), Rothkopf claims that the Bryan method, which is widely used to obtain the solution in the maximum entropy method and makes use of the singular value decomposition of a matrix, limits the search space for the solution. He even presents a counterexample to the Bryan method. In this comment, we first recapitulate the mathematical basis of the Bryan method, and reconfirm that it makes use of no approximations and that it is therefore mathematically rigorous. In the second part, we explicitly show that Rothkopf's ``counterexample'' actually does not constitute a counterexample on the basis of the definition of singular value decomposition itself.

   hep-phhep-latnucl-th7 citations
7. 07*

   Coulomb-nuclear interference in elastic scattering: eikonal calculation to all orders of $\alpha$

   Jan Kašpar🇨🇿

   The Coulomb-nuclear interference (CNI) has recently been used by the TOTEM Collaboration to analyse proton-proton elastic-scattering data from the LHC and to draw physics conclusions. This paper will present an eikonal calculation of the CNI effects performed to all orders of the fine structure constant, $\alpha$. This calculation will be used as a reference to benchmark several widely-used CNI formulae and to verify several recent claims by other authors.

   hep-phnucl-thActa Phys.Polon.B(2021)·9 citations
8. 08*

   Impact of dijet and D-meson data from 5.02 TeV p+Pb collisions on nuclear PDFs

   Kari J. Eskola🇫🇮 · Ilkka Helenius🇫🇮 · Petja Paakkinen🇪🇸 · Hannu Paukkunen🇫🇮

   We discuss the new constraints on gluon parton distribution function (PDF) in lead nucleus, derivable with the Hessian PDF reweighting method from the 5.02 TeV p+Pb measurements of dijet (CMS) and $D^0$-meson (LHCb) nuclear modification ratios. The impact is found to be significant, placing stringent constraints in the mid- and previously unconstrained small-$x$ regions. The CMS dijet data confirm the existence of gluon anti-shadowing and the onset of small-$x$ shadowing, as well as reduce the gluon PDF uncertainties in the larger-$x$ region. The gluon constraints from the LHCb $D^0$ data, reaching down to $x\sim 10^{-5}$ and derived in a NLO perturbative QCD approach, provide a remarkable reduction of the small-$x$ uncertainties with a strong direct evidence of gluon shadowing. Furthermore, we find a good description of the data even down to zero $D^0$-meson transverse momentum within a purely DGLAP-based approach without a need for imposing any non-linear effects. Importantly, the constraints obtained from the dijet and $D^0$ data are mutually fully consistent, supporting the universality of nuclear PDFs in hard-scattering processes.

   hep-phNPA(2021)·4 citations
9. 09*

   Sum rule improved double parton distributions in position space

   Markus Diehl🇩🇪 · Jonathan R. Gaunt🇨🇭 · Daniel M. Lang🇩🇪 · Peter Ploessl🇩🇪 · Andreas Schafer🇩🇪

   Models for double parton distributions that are realistic and consistent with theoretical constraints are crucial for a reliable description of double parton scattering. We show how an ansatz that has the correct behaviour in the limit of small transverse distance between the partons can be improved step by step, such as to fulfil the sum rules for double parton distributions with an accuracy around 10%.

   hep-phEPJC(2020)·29 citations
10. 10*

    Comparing 2HDM $+$ Scalar and Pseudoscalar Simplified Models at LHC

    Giorgio Arcadi🇮🇹 · Giorgio Busoni🇩🇪 · Thomas Hugle🇩🇪 · Valentin Titus Tenorth🇩🇪

    In this work we compare the current experimental LHC limits of the 2HDM $+$ scalar and pseudoscalar for the $t\bar{t}$, mono-$Z$ and mono-$h$ signatures and forecast the reach of future LHC upgrades for the mono-$Z$ channel. Furthermore, we comment on the possibility, in case of a signal detection, to discriminate between the two models. The 2HDM+S and 2HDM+PS are two notable examples of the so-called next generation of Dark Matter Simplified Models. They allow for a renormalizable coupling of fermionic, Standard Model singlet, Dark Matter with a two Higgs doublet sector, through the mixing of the latter with a scalar or pseudoscalar singlet.

    hep-phhep-exJHEP(2020)·40 citations
11. 11*

    Multiple point principle in the general Two-Higgs-Doublet model

    Markos Maniatis🇨🇱 · Lohan Sartore🇫🇷 · Ingo Schienbein🇫🇷

    Based on the Multiple Point Principle, the Higgs boson mass has been predicted to be 135 +- 9 GeV - more than two decades ago. We study the Multiple Point Principle and its prospects with respect to the Two-Higgs-Doublet model (THDM). Applying the bilinear formalism we show that concise conditions can be given with a classification of different kinds of realizations of this principle. We recover cases discussed in the literature but identify also different realizations of the Multiple Point Principle.

    hep-phJHEP(2020)·6 citations
12. 12*

    Relative Scales of the GUT and Twin Sectors in an F-theory model

    C. Herbert Clemens · Stuart Raby🇺🇸

    In this letter we analyze the relative scales for the GUT and twin sectors in the F-theory model discussed in Ref. \cite{Clemens-3}. There are a number of volume moduli in the model. The volume of the GUT surface in the visible sector {[}sector(1){]} (with the Wilson line GUT breaking) defines the GUT scale $M_{GUT}\sim 2\times 10^{16}GeV$ as the unification scale with precise gauge coupling unification of $SU(3)\times SU(2)\times U(1{)}_Y$. We choose ${\alpha }_{GUT}^{-1}\sim 24$. We are then free to choose the ratio ${\alpha }_G(2)/{\alpha }_G(1)=m_1/m_2$ with $m(1)$ and $m(2)$ independent volume moduli associated with the directions perpendicular to the two GUT surfaces. We then analyze the effective field theory of the twin sector(2), which may lead to a SUSY breaking gaugino condensate. Of course, all these results are subject to the self-consistent stabilization of the moduli.

    ↳ hep-thhep-phJHEP(2020)·11 citations
13. 13*

    Tracing the high energy theory of gravity: an introduction to Palatini inflation

    Tommi Tenkanen🇺🇸

    We present an introduction to cosmic inflation in the context of Palatini gravity, which is an interesting alternative to the usual metric theory of gravity. In the latter case only the metric $g_{\mu \nu }$ determines the geometry of space-time, whereas in the former case both the metric and the space-time connection ${\Gamma }_{\mu \nu }^{\lambda }$ are a priori independent variables - a choice which can lead to a theory of gravity different from the metric one. In scenarios where the field(s) responsible for cosmic inflation are coupled non-minimally to gravity or the gravitational sector is otherwise extended, assumptions of the underlying gravitational degrees of freedom can have a big impact on the observational consequences of inflation. We demonstrate this explicitly by reviewing several interesting and well-motivated scenarios including Higgs inflation, $R^2$ inflation, and $\xi$-attractor models. We also discuss some prospects for future research and argue why $r=10^{-3}$ is a particularly important goal for future missions that search for signatures of primordial gravitational waves.

    ↳ astro-ph.COgr-qchep-phGen.Rel.Grav.(2020)·86 citations
14. 14*

    Validation and improvement of the ZPC parton cascade inside a box

    Xin-Li Zhao🇨🇳 · Guo-Liang Ma🇨🇳 · Yu-Gang Ma🇨🇳 · Zi-Wei Lin🇺🇸

    Cascade solutions of the Boltzmann equation suffer from causality violation at large densities and/or scattering cross sections. Although the particle subdivision technique can reduce the causality violation, it alters event-by-event correlations and fluctuations and is also computationally expensive. Here we evaluate and then improve the accuracy of the ZPC parton cascade for elastic scatterings inside a box without using parton subdivision. We first test different collision schemes for the collision times and ordering time and find that the default collision scheme does not accurately describe the equilibrium momentum distribution at large opacities. We then find a specific collision scheme that can describe very accurately the equilibrium momentum distribution as well as the time evolution towards equilibrium, even at large opacities. We also calculate the shear viscosity and the $\eta /s$ ratio of the parton systems and confirm that the new collision scheme is more accurate. In addition, we use a novel parton subdivision method to obtain the "exact" evolution of the system. This subdivision method is valid for such box calculations and is so much more efficient than the standard subdivision method that we use a subdivision factor of $10^6$ in this study.

    ↳ nucl-thhep-phPRC(2020)·10 citations
15. 15*

    BLUE: combining correlated estimates of physics observables within ROOT using the Best Linear Unbiased Estimate method

    Richard Nisius🇩🇪

    This software performs the combination of $m$ correlated estimates of $n$ physics observables ($m\ge n$) using the Best Linear Unbiased Estimate (BLUE) method. It is implemented as a C++ class, to be used within the ROOT analysis package. It features easy disabling of specific estimates or uncertainty sources, the investigation of different correlation assumptions, and allows performing combinations according to the importance of the estimates. This enables systematic investigations of the combination on details of the measurements from within the software, without touching the input.

    ↳ physics.data-anhep-exhep-phSoftwareX 11 (2020) 100468·35 citations
16. 16*

    Color Confinement and Bose-Einstein Condensation

    Masanori Hanada🇬🇧 · Hidehiko Shimada🇯🇵 · Nico Wintergerst🇩🇰

    We propose a unified description of two important phenomena: color confinement in large-$N$ gauge theory, and Bose-Einstein condensation (BEC). We focus on the confinement/deconfinement transition characterized by the increase of the entropy from $N^0$ to $N^2$, which persists in the weak coupling region. Indistinguishability associated with the symmetry group -- SU($N$) or O($N$) in gauge theory, and S${}_N$ permutations in the system of identical bosons -- is crucial for the formation of the condensed (confined) phase. We relate standard criteria, based on off-diagonal long range order (ODLRO) for BEC and the Polyakov loop for gauge theory. The constant offset of the distribution of the phases of the Polyakov loop corresponds to ODLRO, and gives the order parameter for the partially-(de)confined phase at finite coupling. We demonstrate this explicitly for several quantum mechanical systems (i.e., theories at small or zero spatial volume) at weak coupling, and argue that this mechanism extends to large volume and/or strong coupling. This viewpoint may have implications for confinement at finite $N$, and for quantum gravity via gauge/gravity duality.

    ↳ hep-thhep-lathep-phJHEP(2021)·37 citations
17. 17*

    The Atacama Cosmology Telescope: Constraints on Cosmic Birefringence

    Toshiya Namikawa🇬🇧 · Yilun Guan🇺🇸 · Omar Darwish🇬🇧 · Blake D. Sherwin🇬🇧 · Simone Aiola🇺🇸 · Nicholas Battaglia🇺🇸 · James A. Beall🇺🇸 · Daniel T. Becker🇺🇸 · J. Richard Bond🇨🇦 · Erminia Calabrese🇬🇧 · Grace E. Chesmore🇺🇸 · Steve K. Choi🇺🇸 and 42 other authors

    We present new constraints on anisotropic birefringence of the cosmic microwave background polarization using two seasons of data from the Atacama Cosmology Telescope covering $456$ square degrees of sky. The birefringence power spectrum, measured using a curved-sky quadratic estimator, is consistent with zero. Our results provide the tightest current constraint on birefringence over a range of angular scales between $5$ arcminutes and $9$ degrees. We improve previous upper limits on the amplitude of a scale-invariant birefringence power spectrum by a factor of between $2$ and $3$. Assuming a nearly-massless axion field during inflation, our result is equivalent to a $2\sigma$ upper limit on the Chern-Simons coupling constant between axions and photons of $g_{\alpha \gamma }<4.0\times 10^{-2}/H_I$ where $H_I$ is the inflationary Hubble scale.

    ↳ astro-ph.COhep-exhep-phPRD(2020)·111 citations
18. 18*

    The analytic structure of amplitudes on backgrounds from gauge invariance and the infra-red

    Anton Ilderton🇬🇧 · Alexander J. MacLeod🇬🇧

    Gauge invariance and soft limits can be enough to determine the analytic structure of scattering amplitudes in certain theories. This prompts the question of how gauge invariance is connected to analytic structure in more general theories. Here we focus on QED in background plane waves. We show that imposing gauge invariance introduces new virtuality poles into internal momenta on which amplitudes factorise into a series of terms. Each term is gauge invariant, has a different analytic structure in external momenta, and exhibits a hard/soft factorisation. The introduced poles are dictated by infra-red behaviour, which allows us to extend our results to scalar Yukawa theory. The background is treated non-perturbatively throughout.

    ↳ hep-thhep-phJHEP(2020)·18 citations
19. 19*

    Particle Theory at Chicago in Late Sixties and p-Adic Strings

    Paul H. Frampton🇮🇹

    As a contribution requested by the editors of a Memorial Volume for Peter G.O. Freund (1936-2018), we recall the lively particle theory group at the Enrico Fermi Institute of the University of Chicago in the late sixties, of which Peter was a memorable member. We also discuss a period some twenty years later when our and Peter's research overlapped on the topic of p-adic strings.

    ↳ physics.hist-phhep-phhep-thJ.Phys.A(2020)·3 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.