Thu·Dec 19, 2019Thursday·December 19, 2019

1. 01*

   Effective charge from lattice QCD

   Zhu-Fang Cui🇨🇳 · Jin-Li Zhang🇨🇳 · Daniele Binosi🇮🇹 · Feliciano De Soto🇪🇸 · Cédric Mezrag🇫🇷 · Joannis Papavassiliou🇪🇸 · Craig D. Roberts🇨🇳 · Jose Rodríguez-Quintero🇪🇸 · Jorge Segovia🇪🇸 · Savvas Zafeiropoulos🇫🇷

   Using lattice configurations for quantum chromodynamics (QCD) generated with three domain-wall fermions at a physical pion mass, we obtain a parameter-free prediction of QCD's renormalisation-group-invariant process-independent effective charge, $\hat{\alpha }(k^2)$. Owing to the dynamical breaking of scale invariance, evident in the emergence of a gluon mass-scale, this coupling saturates at infrared momenta: $\hat{\alpha }(0)/\pi =0.97(4)$. Amongst other things: $\hat{\alpha }(k^2)$ is almost identical to the process-dependent (PD) effective charge defined via the Bjorken sum rule; and also that PD charge which, employed in the one-loop evolution equations, delivers agreement between pion parton distribution functions computed at the hadronic scale and experiment. The diversity of unifying roles played by $\hat{\alpha }(k^2)$ suggests that it is a strong candidate for that object which represents the interaction strength in QCD at any given momentum scale; and its properties support a conclusion that QCD is a mathematically well-defined quantum field theory in four dimensions.

   hep-phhep-exhep-latnucl-ex+1CPC(2020)·144 citations
2. 02*

   The Radiation Valley and Exotic Resonances in $W\gamma$ Production at the LHC

   Rodolfo M. Capdevilla🇨🇦 · Roni Harnik🇺🇸 · Adam Martin🇺🇸

   The tree-level partonic angular distribution of Standard Model $W\gamma$ production possesses a feature known as the Radiation Amplitude Zero (RAZ) where destructive interference causes the cross section to vanish. At the proton level the exact cancellation disappears, however, one can find a dip in the central region of the angular distributions, here called the Radiation Valley (RV). In this paper, we show how the sensitivity for $W(\ell \nu )\gamma$ resonances can be significantly improved if one focuses on events in the RV region. Using this technique, we find that the LHC could probe a larger range of resonance masses, equivalent to increasing the luminosity by a factor of $2-3$ over conventional searches. The exact increase depends on the spin of the $W\gamma$ resonance and exactly how it couples to electroweak gauge bosons.

   hep-phJHEP(2020)·19 citations
3. 03*

   Y(4626) as a molecular state from interaction $D_s^{\ast }{\bar{D}}_{s1}(2536)-D_s{\bar{D}}_{s1}(2536)$

   Jun He🇨🇳 · Yi Liu🇨🇳 · Jun-Tao Zhu🇨🇳 · Dian-Yong Chen🇨🇳

   Recently, a new structure $Y(4626)$ was reported by the Belle Colloboration in the process $e^{+}{e}^{-}\to D_s^{+}{D}_{s1}(2536{)}^{-}$. In this work, we propose an assignment of the $Y(4626)$ as a $D_s^{\ast }{\bar{D}}_{s1}(2536)$ molecular state, which decays into the $D_s^{+}{D}_{s1}(2536{)}^{-}$ channel through a coupling between $D_s^{\ast }{\bar{D}}_{s1}(2536)$ and $D_s{\bar{D}}_{s1}(2536)$ channels. With the help of the heavy quark symmetry, the potential of the interaction $D_s^{\ast }{\bar{D}}_{s1}(2536)-D_s{\bar{D}}_{s1}(2536)$ is constructed within the one-boson-exchange model, and inserted into the quasipotential Bethe-Salpeter equation. The pole of obtained scattering amplitude is searched for in the complex plane, which corresponds to a molecular state from the interaction $D_s^{\ast }{\bar{D}}_{s1}(2536)-D_s{\bar{D}}_{s1}(2536)$. The results suggest that a pole is produced near the $D_s^{\ast }{\bar{D}}_{s1}(2536)$ threshold, which exhibits as a peak in the invariant mass spectrum of the $D_s{\bar{D}}_{s1}(2536)$ channel at about 4626 MeV. It obviously favors the $Y(4265)$ as a $D_s^{\ast }{\bar{D}}_{s1}(2536)$ molecular state. In the same model, other molecular states from the interaction $D_s^{\ast }{\bar{D}}_{s1}(2536)-D_s{\bar{D}}_{s1}(2536)$ are also predicted, which can be checked in future experiments.

   hep-phEPJC(2020)·28 citations
4. 04*

   Non-leptonic B-decays at two loops in QCD Factorization

   Guido Bell🇩🇪 · Martin Beneke🇩🇪 · Tobias Huber🇩🇪 · Xin-Qiang Li🇨🇳

   We report on the calculation of the two-loop penguin amplitudes in non-leptonic B decays in the framework of QCD factorization. We discuss the computation of this genuine two-loop, two-scale problem and provide details on the matching from QCD onto SCET, the evaluation of the master integrals, and the convolution of the hard scattering kernels with the light-cone distribution amplitude of the light meson. Preliminary results on the size of the two-loop correction are given.

   hep-phPoS(2019)·3 citations
5. 05*

   DUNE potential for sub-GeV dark matter in proton beam dump mode

   Sabeeha Naaz🇮🇳 · Jyotsna Singh🇮🇳 · R. B. Singh🇮🇳

   DUNE with its cutting edge technology is designed to study the neutrino science and proton decay physics. This facility can be further exploited for the study of the ground breaking discoveries i.e. origin of matter, unification of forces, dark matter detection etc. In this work we have explored the DUNE potential for capturing the sub-GeV dark matter in viable dark matter parameter space. The scenario of sub-GeV dark matter range requires a light mediator that couples the hidden sector with the standard model. The choice of the mediator will decide the different channels by which dark matter candidates can be produced. Here three channels ${\pi }^0/\eta$-decay, proton bremsstrahlung and parton-level production modes are considered for the production of dark matter with a 120 GeV proton beam facility placed at Fermi lab. To overcome the neutrino background we have used beam dump mode for the production of pure dark matter beam. To explore the new region of parameter space of dark matter at DUNE the elastic scattering of dark matter beam with electrons and nucleons are studied. In terms of DUNE potential for capturing dark matter signatures the dark matter yield results at DUNE (in our work) shows a significant improvement over existing dark matter probes i.e. BaBar, E137, LSND, MiniBooNE, T2K etc.

   hep-phJournal of University of Shanghai for Sci…·3 citations
6. 06*

   Probing Higgs-portal dark matter with vector-boson fusion

   Jan Heisig🇧🇪 · Michael Krämer🇩🇪 · Eric Madge🇩🇪 · Alexander Mück🇩🇪

   We constrain the Higgs-portal model employing the vector-boson fusion channel at the LHC. In particular, we include the phenomenologically interesting parameter region near the Higgs resonance, where the Higgs-boson mass is close to the threshold for dark-matter production and a running-width prescription has to be employed for the Higgs-boson propagator. Limits for the Higgs-portal coupling as a function of the dark-matter mass are derived from the CMS search for invisible Higgs-boson decays in vector-boson fusion at 13 TeV. Furthermore, we perform projections for the 14 TeV HL-LHC and the 27 TeV HE-LHC taking into account a realistic estimate of the systematic uncertainties. The respective upper limits on the invisible branching ratio of the Higgs boson reach a level of 2 % and constrain perturbative Higgs-portal couplings up to dark-matter masses of about 110 GeV.

   hep-phJHEP(2020)·23 citations
7. 07*

   NLO QCD + electroweak predictions for off-shell ttH production at the LHC

   Ansgar Denner🇩🇪 · Jean-Nicolas Lang🇨🇭 · Mathieu Pellen🇬🇧 · Sandro Uccirati🇮🇹

   In these proceedings, next-to-leading-order (NLO) QCD and electroweak (EW) corrections to $\mathrm{p}\mathrm{p}\to {\mathrm{e}}^{+}{\nu }_{\mathrm{e}}{\mu }^{-}{\bar{\nu }}_{\mu }\mathrm{b}\bar{\mathrm{b}}\mathrm{H}$ at the LHC are presented. In these computations the top quarks are considered off their mass shell and all non-resonant contributions are included. The results are presented in the form of fiducial cross sections and differential distributions. Moreover, two prescriptions to combine QCD and EW corrections are examined.

   hep-phhep-ex1 citation
8. 08*

   Collider Constraints on Lepton Flavor Violation in the 2HDM

   R. Primulando🇮🇩 · J. Julio🇮🇩 · P. Uttayarat🇹🇭

   In light of the recent CMS analysis on lepton flavor violating (LFV) heavy Higgs searches and updated bounds on various search channels involving neutral and charged scalars, we provide the updated constraints on the Type-III Two-Higgs-Doublet-Model (2HDM) with a $\tau -\mu$ LFV. In doing so, we first extend the CMS analysis to cover the mass region below 200 GeV by recasting their data. After obtaining the bounds on the heavy Higgs production in the mass range between 130 GeV and 450 GeV, we analyze the parameter space of the Type-III 2HDM with various scenarios of mass spectrum and heavy Higgs production strengths. We found that in most scenarios, searching for the heavy Higgs in the mass range lower than $2m_W$ is very important in constraining the parameter space of the Type-III 2HDM. Hence, we suggest for the future analysis that the search window for the LFV heavy Higgs be extended to the lower mass region.

   hep-phPRD(2020)·21 citations
9. 09*

   Gluon Bremsstrahlung in Relativistic Heavy Ion Collisions

   Mawande Lushozi🇺🇸 · Larry D. McLerran🇺🇸 · Michał Praszalowicz🇵🇱 · Gongming Yu🇺🇸

   We study the process $qq\to qqg$ at lowest order in QCD perturbation theory to understand gluon radiation in the fragmentation region of relativistic heavy-ion collisions. We arrive at a formula for gluon multiplicity that interpolates between $\sim 1/k_{\perp }^2$ behavior at low $k_{\perp }$, to $\sim 1/k_{\perp }^4$ at large $k_{\perp }$.

   hep-phPRC(2020)·7 citations
10. 10*

    On Resolving the Dark LMA Solution at Neutrino Oscillation Experiments

    Sandhya Choubey🇸🇪 · Dipyaman Pramanik🇮🇳

    In presence of non standard interactions, the solar neutrino data is consistent with two solutions, one close to the standard LMA solution with ${\sin }^2{\theta }_{12}\simeq 0.3$ and another with ${\sin }^2{\theta }_{12}^D\simeq 0.7(={\cos }^2{\theta }_{12})$. The latter has been called the Dark LMA (DLMA) solution in the literature. This issue is hard to resolve via oscillations because of the existence of the so-called "generalised mass hierarchy" degeneracy of the neutrino mass matrix in presence of NSI. However, if the mass hierarchy is independently determined in a non-oscillation experiment such as neutrino-less double beta decay, the invariance of neutrino oscillation probabilities under ${\sin }^2{\theta }_{12}\leftrightarrow {\cos }^2{\theta }_{12}$ is lost and the possibility of resolving the LMA vs DLMA opens up. We point out that the $P_{\mu \mu }$ channel can distinguish ${\theta }_{12}$ from ${\theta }_{12}^D$ and study the corresponding difference in long-baseline experiments. We show that a key ingredient required is the input from the $P_{ee}$ channel measured at a reactor experiment. We find that if the mass hierarchy is determined by neutrino-less double beta decay, then a combined measurement of the effective mass squared differences in long-baseline experiments such as T2HK and DUNE and reactor experiment such as JUNO can resolve the DLMA conundrum to better than $3\sigma$ within 1 year for T2HK and little more than 3 years for DUNE.

    hep-phJHEP(2020)·8 citations
11. 11*

    Charged pion condensation in dense quark matter: Nambu--Jona-Lasinio model study

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

    In this short review we tried to give an outline of investigations of charged pion condensation (PC) in dense baryonic (quark) matter in the framework of effective Nambu--Jona-Lasinio (NJL) type models. The possibility of charged PC phase in dense quark matter with isospin asymmetry is investigated. First, it is demonstrated that this phase can be realized in the framework of massless NJL model. But the existence of this phase is enormously fragile to the values of current quark mass %.Then, and we show that charged PC phase is forbidden in electrically neutral dense quark matter with $\beta$-equilibrium when current quark masses are close to their physical value of 5.5 MeV. Nevertheless, then it is shown that in real physical systems there could be conditions promoting the appearance of charged PC phenomenon in dense quark matter, namely, it was shown that if one includes into consideration the fact that system can have finite size, then a dense charged PC phase can be realized there. It was also demonstrated that the possibility of inhomogeneous pion condensate might allow this phase to appear. And more recently it was revealed that there is another interesting factor that can induce a charged PC phase in dense quark matter even without isospin imbalance. It is a chiral imbalance of the system (non-zero difference between densities of left- and right-handed quarks). This results can be interesting in heavy ion collision experiments, where it is expected to get high baryon densities. It is of interest also in the context of the neutron stars, where quark matter might be realized in the core and very high baryon and isospin densities are attained.

    hep-phhep-thnucl-thSymmetry(2019)·27 citations
12. 12*

    Testing Lepton Flavour Universality with (Semi)-Leptonic $D_{(s)}$ Decays

    Robert Fleischer🇳🇱 · Ruben Jaarsma🇳🇱 · Gabriël Koole🇩🇪

    Data in $B$-meson decays indicate violations of lepton flavour universality, thereby raising the question about such phenomena in the charm sector. We perform a model-independent analysis of NP contributions in (semi)-leptonic decays of $D_{(s)}$ mesons which originate from $c\to d\bar{\ell }{\nu }_{\ell }$ and $c\to s\bar{\ell }{\nu }_{\ell }$ charge-current interactions. Starting from the most general low-energy effective Hamiltonian containing four-fermion operators and the corresponding short-distance coefficients, we explore the impact of new (pseudo)-scalar, vector and tensor operators and constrain their effects through the interplay with current data. We pay special attention to the elements $|V_{cd}|$ and $|V_{cs}|$ of the Cabibbo--Kobayashi--Maskawa matrix and extract them from the $D_{(s)}$ decays in the presence of possible NP decay contributions, comparing them with determinations utilizing unitarity. We find a picture in agreement with the Standard Model within the current uncertainties. Using the results from our analysis, we make also predictions for leptonic $D_{(s)}^{+}\to e^{+}{\nu }_e$ modes which could be hugely enhanced with respect to their tiny Standard Model branching ratios. It will be interesting to apply our strategy at the future high-precision frontier.

    hep-phhep-exEPJC(2020)·32 citations
13. 13*

    Four-jet double parton scattering production in proton-nucleus collisions within the PYTHIA8 framework

    Oleh Fedkevych🇮🇹 · Leif Lönnblad🇸🇪

    We present our studies of four-jet double parton scattering production in proton-nucleus collisions within the framework of the PYTHIA8 event generator. We demonstrate that double absorptive processes in pA generated by the Angantyr model in PYTHIA8 give an enhancement of the total double parton scattering cross section similar to the predictions by Strikman and Treleani in 2001. Additionally, we discuss how the growth of activity in a direction of a nucleus affects an A-scaling of a total double parton scattering cross section in proton-nucleus collisions.

    hep-phPRD(2020)·9 citations
14. 14*

    Smearing of causality by compositeness divides dispersive approaches into exact ones and precision-limited ones

    Felipe J. Llanes-Estrada🇪🇸 · Raul Roldan-Gonzalez (Univ. Complutense of Madrid)🇪🇸

    Scattering off the edge of a composite particle or finite-range interaction can precede that off its center. An effective theory treatment with pointlike particles and contact interactions must find that the scattered experimental wave is slightly advanced, in violation of causality (the fundamental underlying theory being causal). In practice, partial-wave or other projections of multivariate amplitudes exponentially grow with imaginary E, so that upper complex-plane analyticity is not sufficient to obtain a dispersion relation for them, but only for a slightly modified function (the modified relations additionally connect different J). This limits the maximum precision of certain dispersive approaches to compositeness based on Cauchy's theorem leading to partial-wave dispersion relations. This may be of interest to some dispersive tests of the Standard Model with hadrons, and to unitarization methods used to extend electroweak effective theories. Interestingly, the Inverse Amplitude Method is safe (as the inverse amplitude has the opposite, convergent behavior allowing contour closure). Generically, one-dimensional sum rules such as for the photon vacuum polarization, one-dimensional form factors or the Adler function, to name a few, are not affected by this uncertainty. Likewise, fixed-t dispersion relations were cleverly constructed to avoid it and consequences therefrom are solid.

    hep-phnucl-thSciPost Phys.Core(2022)·7 citations
15. 15*

    Covariant multipole expansion of local currents for massive states of any spin

    Sabrina Cotogno🇫🇷 · Cédric Lorcé🇫🇷 · Peter Lowdon🇫🇷 · Manuel Morales🇨🇭

    We study the structure of scalar, vector, and tensor currents for on-shell massive particles of any spin. When considering higher values for the spin of the particle, the number of form factors (FFs) involved in the decomposition of the matrix elements associated with these local currents increases. We identify all the fundamental structures that give rise to the independent FFs, systematically for any spin value. These structures can be conveniently organised using an expansion in covariant multipoles, built solely from the Lorentz generators. This approach allows one to uniquely identify the terms which are universal and those that arise because of spin. We derive counting rules which relate the number of FFs to the total spin $j$ of the state, showing explicitly that these rules match all the well-known cases up to spin 2.

    hep-phhep-thnucl-thPRD(2020)·66 citations
16. 16*

    On the two-loop amplitude for $gg\to ZZ$ production with full top-mass dependence

    Bakul Agarwal🇺🇸 · Andreas von Manteuffel🇺🇸

    In this talk, we discuss top-quark contributions to $ZZ$ production through gluon fusion at two loops. We use syzygies and modular arithmetic to compute the reductions to master integrals. In order to numerically evaluate the amplitude, we express it in terms of finite integrals using a new method to construct integrable linear combinations of divergent integrands.

    hep-phPoS(2019)·10 citations
17. 17*

    Direct baryogenesis in the broken phase

    Takehiko Asaka🇯🇵 · Hiroyuki Ishida🇯🇵 · Wen Yin🇰🇷

    We show a new mechanism for baryogenesis where the reheating temperature can be smaller than the electroweak scale. The baryon number symmetry is violated by a dimension nine operator which conserves a baryon parity. A high energy quark from the decay of a heavy particle, $e.g.$ inflaton, modulus or gravitino, undergoes flavor oscillation, and is thermalized due to the scatterings with the ambient thermal plasma. We point out that the baryon asymmetry of our universe can be generated due to the scatterings via the baryon number violating operator. Our scenario can be tested in neutron-antineutron oscillation experiments as well as other terrestrial experiments.

    hep-phastro-ph.COJHEP(2020)·24 citations
18. 18*

    An exploratory study of the impact of CMS double-differential top distributions on the gluon parton distribution function

    Michał Czakon🇩🇪 · Sayipjamal Dulat🇨🇳 · Tie-Jiun Hou🇨🇳 · Joey Huston🇺🇸 · Alexander Mitov🇬🇧 · Andrew S. Papanastasiou🇬🇧 · Ibrahim Sitiwaldi🇨🇳 · Zhite Yu🇺🇸 · C.--P. Yuan🇺🇸

    LHC $t\bar{t}$ data have the potential to provide constraints on the gluon distribution, especially at high $x$, with both ATLAS and CMS performing differential measurements. Recently, CMS has measured double-differential $t\bar{t}$ distributions at 8 TeV. In this paper we examine the impact of this data set on the gluon distribution. To that end we develop novel, double-differential NNLO predictions for that data. No significant impact is found when the CMS data is added to the CT14HERA2 global PDF fit, due to the larger impact of the inclusive jet data from both the Tevatron and the LHC. If the jet data are removed from the fit, then an impact is observed. If the CMS data is scaled by a larger weight, representing the greater statistical power of the jet data, a roughly equal impact on the gluon distribution is observed for the $t\bar{t}$ as for the inclusive jet data. For data samples with higher integrated luminosity at 13 TeV, a more significant impact of the double-differential $t\bar{t}$ data may be observed.

    hep-phhep-exJ.Phys.G(2020)·31 citations
19. 19*

    Functional Methods for Heavy Quark Effective Theory

    Timothy Cohen🇺🇸 · Marat Freytsis🇺🇸 · Xiaochuan Lu🇺🇸

    We use functional methods to compute one-loop effects in Heavy Quark Effective Theory. The covariant derivative expansion technique facilitates the efficient extraction of matching coefficients and renormalization group evolution equations. This paper provides the first demonstration that such calculations can be performed through the algebraic evaluation of the path integral for the class of effective field theories that are (i) constructed using a non-trivial one-to-many mode decomposition of the UV theory, and (ii) valid for non-relativistic kinematics. We discuss the interplay between operators that appear at intermediate steps and the constraints imposed by the residual Lorentz symmetry that is encoded as reparameterization invariance within the effective description. The tools presented here provide a systematic approach for computing corrections to higher order in the heavy mass expansion; precision applications include predictions for experimental data and connections to theoretical tests via lattice QCD. A set of pedagogical appendices comprehensively reviews modern approaches to performing functional calculations algebraically, and derives contributions from a term with open covariant derivatives for the first time.

    hep-phJHEP(2020)·27 citations
20. 20*

    Radio Signal of Axion-Photon Conversion in Neutron Stars: A Ray Tracing Analysis

    Mikaël Leroy🇳🇱 · Marco Chianese🇳🇱 · Thomas D.P. Edwards🇳🇱 · Christoph Weniger🇳🇱

    Axion dark matter can resonantly convert into photons in the magnetospheres of neutron stars (NSs). It has recently been shown that radio observations of nearby NSs can therefore provide a highly sensitive probe of the axion parameter space. Here we extend existing calculations by performing the first three-dimensional computation of the photon flux, taking into account the isotropic phase-space distribution of axions and the structure of the NS magnetosphere. In particular, we study the overall magnitude of the flux and its possible time variation. We find that overall signal strength is robust to our more realistic analysis. In addition, we find that the variance of the signal with respect to the NS rotation is washed out by the additional trajectories in our treatment. Nevertheless, we show that SKA observations towards J0806.4-4123 are sensitive to $g_{a\gamma \gamma }\sim 3\times 10^{-13}\mathrm{Ge}{\mathrm{V}}^{-1}$ at $m_a\sim 7\times 10^{-6}\mathrm{eV}$, even when accounting for Doppler broadening. Finally, we provide the necessary code to calculate the photon flux for any given NS system.

    hep-phPRD(2020)·110 citations
21. 21*

    Scalars Gliding Through an Expanding Universe

    Anson Hook🇺🇸 · Gustavo Marques-Tavares🇺🇸 · Yuhsin Tsai🇺🇸

    In this article we investigate the effects of single derivative mixing in massive bosonic fields. In the regime of large mixing, we show that this leads to striking changes of the field dynamics, delaying the onset of classical oscillations and decreasing, or even eliminating, the friction due to Hubble expansion. We highlight this phenomenon with a few examples. In the first example, we show how an axion like particle can have its number abundance parametrically enhanced. In the second example, we demonstrate that the QCD axion can have its number abundance enhanced allowing for misalignment driven axion dark matter all the way down to $f_a$ of order astrophysical bounds. In the third example, we show that the delayed oscillation of the scalar field can also sustain a period of inflation. In the last example, we present a situation where an oscillating scalar field is completely frictionless and does not dilute away in time.

    hep-phastro-ph.COPRL(2020)·18 citations
22. 22*

    Factorization at Subleading Power and Endpoint-Divergent Convolutions in $h\to \gamma \gamma$ Decay

    Ze Long Liu (Los Alamos Nat. Lab.)🇺🇸 · Matthias Neubert (MITP, Johannes Gutenberg Univ. Mainz)🇩🇪

    It is by now well known that, at subleading power in scale ratios, factorization theorems for high-energy cross sections and decay amplitudes contain endpoint-divergent convolution integrals. The presence of these divergences hints at a violation of simple scale separation, as a result of the so-called collinear anomaly. At the technical level, endpoint divergences indicate an unexpected failure of dimensional regularization and the $\overline{\mathrm{MS}}$ subtraction scheme. In this paper we start a comprehensive discussion of factorization at subleading power within the framework of soft-collinear effective theory. As a concrete example, we factorize the decay amplitude for the radiative Higgs-boson decay $h\to \gamma \gamma$ mediated by a $b$-quark loop, for which endpoint-divergent convolution integrals require both dimensional and rapidity regulators. We derive a factorization theorem for the decay amplitude in terms of bare Wilson coefficients and operator matrix elements. We show that endpoint divergences caused by rapidity divergences cancel to all orders in perturbation theory, while endpoint divergences that are regularized dimensionally can be removed by rearranging the terms in the factorization theorem. We use our result to resum the leading double-logarithmic corrections of order ${\alpha }_s^n{\ln }^{2n+2}(-M_h^2/m_b^2)$ to all orders of perturbation theory.

    hep-phhep-thJHEP(2020)·115 citations
23. 23*

    A Systematic Study of Hidden Sector Dark Matter: Application to the Gamma-Ray and Antiproton Excesses

    Dan Hooper🇺🇸 · Rebecca K. Leane🇺🇸 · Yu-Dai Tsai🇺🇸 · Shalma Wegsman🇺🇸 · Samuel J. Witte🇪🇸

    In hidden sector models, dark matter does not directly couple to the particle content of the Standard Model, strongly suppressing rates at direct detection experiments, while still allowing for large signals from annihilation. In this paper, we conduct an extensive study of hidden sector dark matter, covering a wide range of dark matter spins, mediator spins, interaction diagrams, and annihilation final states, in each case determining whether the annihilations are s-wave (thus enabling efficient annihilation in the universe today). We then go on to consider a variety of portal interactions that allow the hidden sector annihilation products to decay into the Standard Model. We broadly classify constraints from relic density requirements and dwarf spheroidal galaxy observations. In the scenario that the hidden sector was in equilibrium with the Standard Model in the early universe, we place a lower bound on the portal coupling, as well as on the dark matter's elastic scattering cross section with nuclei. We apply our hidden sector results to the observed Galactic Center gamma-ray excess and the cosmic-ray antiproton excess. We find that both of these excesses can be simultaneously explained by a variety of hidden sector models, without any tension with constraints from observations of dwarf spheroidal galaxies.

    hep-phastro-ph.COastro-ph.HEhep-exJHEP(2020)·40 citations
24. 24*

    Global Fit to Modified Neutrino Couplings and the Cabibbo-Angle Anomaly

    Antonio M. Coutinho🇨🇭 · Andreas Crivellin🇨🇭 · Claudio Andrea Manzari🇨🇭

    Recently, discrepancies of up to $4\sigma$ between the different determinations of the Cabibbo angle were observed. This "Cabibbo-angle anomaly" could be explained by lepton flavour universality (LFU) violating New Physics (NP) in the neutrino sector. However, modified neutrino couplings to Standard Model gauge bosons also affect many other observables sensitive to LFU violation which have to be taken into account in order to assess the viability of this explanation. Therefore, we perform a model-independent global analysis in a Bayesian approach and find that the tension in the Cabibbo angle is significantly reduced, while the agreement with other data is also mostly improved. In fact, non-zero modifications of electron and muon neutrino couplings are preferred at more than 99\% CL. Still, since constructive effects in the muon sector are necessary, simple models with right-handed neutrinos (whose global fit we update as a by-product) cannot fully explain data, pointing towards more sophisticated NP models.

    hep-phhep-exhep-latnucl-ex+1PRL(2020)·135 citations
25. 25*

    How to GAN Event Subtraction

    Anja Butter🇩🇪 · Tilman Plehn🇩🇪 · Ramon Winterhalder🇩🇪

    Subtracting event samples is a common task in LHC simulation and analysis, and standard solutions tend to be inefficient. We employ generative adversarial networks to produce new event samples with a phase space distribution corresponding to added or subtracted input samples. We first illustrate for a toy example how such a network beats the statistical limitations of the training data. We then show how such a network can be used to subtract background events or to include non-local collinear subtraction events at the level of unweighted 4-vector events.

    hep-phSciPost Phys.Core(2020)·59 citations
26. 26*

    Enumerating higher-dimensional operators with on-shell amplitudes

    Gauthier Durieux🇮🇱 · Camila S. Machado🇩🇪

    We establish a simple formula for the minimal dimension of operators leading to any helicity amplitude. It eases the systematic enumeration of independent operators from the construction of massless non-factorizable on-shell amplitudes. Little-group constraints can then be solved algorithmically for each helicity configuration to extract a complete set of spinor structures with lowest dimension. Occasionally, further reduction using momentum conservation, on-shell conditions and Schouten identities is required. A systematic procedure to account for the latter is presented. Dressing spinor structures with dot products of momenta finally yields the independent Lorentz structures for each helicity amplitude. We apply these procedures to amplitudes involving particles of spins 0,1/2,1,2. Spin statistics and elementary selection rules due to gauge symmetry lead to an enumeration of operators involving gravitons and standard-model particles, in the effective field theory denoted GRSMEFT. We also list the independent spinor structures generated by operators involving standard-model particles only. In both cases, we cover operators of dimension up to eight.

    hep-phhep-thPRD(2020)·68 citations
27. 27*

    Comments on Global Parton Analyses

    A.D.Martin🇬🇧 · M.G.Ryskin🇷🇺

    We discuss the causes which can limit the accuracy of the predictions based on the conventional PDFs when including in global parton analyses the data at moderate scales $\mu$. The first is the existence of power corrections $\mathcal{O}(Q_0^2/{\mu }^2)$ due to the double counting of contributions arising from the region below the input scale $Q_0$. The second concerns the possible inclusion of the BFKL re-summation of the $({\alpha }_s\ln (1/x){)}^n$ terms. The third is the treatment of the heavy-quark thresholds. We show how to include the heavy-quark masses ($m_h$ with $h=c,b,t$) in DGLAP evolution which provides the correct {\it smooth} behaviour through the threshold regions and how to subtract the low parton virtuality $|k^2|<Q_0^2$ contributions from the DIS and Drell-Yan NLO coefficient functions in order to avoid the double counting.

    hep-phActa Phys.Polon.B(2020)·4 citations
28. 28*

    Proca tubes with the flux of the longitudinal chromoelectric field and the energy flux/momentum density

    Vladimir Dzhunushaliev🇰🇿 · Vladimir Folomeev🇰🇿

    We consider non-Abelian SU(3) Proca theory with a Higgs scalar field included. Cylindrically symmetric solutions describing classical tubes either with the flux of a longitudinal electric field or with the energy flux (and hence with nonzero momentum density) are obtained. It is shown that, in quantum Proca theory, there can exist tubes both with the flux of the longitudinal electric field and with the energy flux/momentum density simultaneously. An imaginary particle -- Proca proton~-- in which `quarks' are connected by tubes with nonzero momentum density is considered. It is shown that this results in the appearance of the angular momentum related to the presence of the non-Abelian electric and magnetic fields in the tube, and this angular momentum is a part of the Proca proton spin.

    hep-phhep-thEPJC(2020)·7 citations
29. 29*

    Machine and Deep Learning Applications in Particle Physics

    Dimitri Bourilkov🇺🇸

    The many ways in which machine and deep learning are transforming the analysis and simulation of data in particle physics are reviewed. The main methods based on boosted decision trees and various types of neural networks are introduced, and cutting-edge applications in the experimental and theoretical/phenomenological domains are highlighted. After describing the challenges in the application of these novel analysis techniques, the review concludes by discussing the interactions between physics and machine learning as a two-way street enriching both disciplines and helping to meet the present and future challenges of data-intensive science at the energy and intensity frontiers.

    ↳ physics.data-anhep-exhep-phphysics.comp-phInt.J.Mod.Phys.A(2020)·131 citations
30. 30*

    Lattice QCD Determination of $g_A$

    André Walker-Loud🇺🇸 · Evan Berkowitz🇺🇸 · David A. Brantley🇺🇸 · Arjun Gambhir🇺🇸 · Pavlos Vranas🇺🇸 · Chris Bouchard🇬🇧 · Chia Cheng Chang🇯🇵 · M. A. Clark🇺🇸 · Nicolas Garron🇬🇧 · Bálint Joó🇺🇸 · Thorsten Kurth🇺🇸 · Henry Monge-Camacho🇺🇸 and 4 other authors

    The nucleon axial coupling, $g_A$, is a fundamental property of protons and neutrons, dictating the strength with which the weak axial current of the Standard Model couples to nucleons, and hence, the lifetime of a free neutron. The prominence of $g_A$ in nuclear physics has made it a benchmark quantity with which to calibrate lattice QCD calculations of nucleon structure and more complex calculations of electroweak matrix elements in one and few nucleon systems. There were a number of significant challenges in determining $g_A$, notably the notorious exponentially-bad signal-to-noise problem and the requirement for hundreds of thousands of stochastic samples, that rendered this goal more difficult to obtain than originally thought. I will describe the use of an unconventional computation method, coupled with "ludicrously'" fast GPU code, access to publicly available lattice QCD configurations from MILC and access to leadership computing that have allowed these challenges to be overcome resulting in a determination of $g_A$ with 1% precision and all sources of systematic uncertainty controlled. I will discuss the implications of these results for the convergence of $SU(2)$ Chiral Perturbation theory for nucleons, as well as prospects for further improvements to $g_A$ (sub-percent precision, for which we have preliminary results) which is part of a more comprehensive application of lattice QCD to nuclear physics. This is particularly exciting in light of the new CORAL supercomputers coming online, Sierra and Summit, for which our lattice QCD codes achieve a machine-to-machine speed up over Titan of an order of magnitude.

    ↳ hep-lathep-phnucl-exnucl-thPoS(2020)·41 citations
31. 31*

    Gluon propagators in QC${}_2$D at high baryon density

    Vitaly Bornyakov🇷🇺 · Andrey Kotov🇷🇺 · Alexander Nikolaev🇬🇧 · Roman Rogalyov🇷🇺

    We study the transverse and longitudinal gluon propagators in the Landau-gauge lattice QCD with gauge group $SU(2)$ at nonzero quark chemical potential and zero temperature. We show that both propagators demonstrate substantial dependence on the quark chemical potential. This observation contradicts to earlier findings by other groups.

    ↳ hep-lathep-phParticles(2020)·5 citations
32. 32*

    $\Lambda \Lambda$ and N$\Xi$ interactions from Lattice QCD near the physical point

    Kenji Sasaki · Sinya Aoki · Takumi Doi · Shinya Gongyo · Tetsuo Hatsuda · Yoichi Ikeda · Takashi Inoue · Takumi Iritani · Noriyoshi Ishii · Keiko Murano · Takaya Miyamoto · (HAL QCD Collaboration)

    The $S$-wave $\Lambda \Lambda$ and $N\Xi$ interactions are studied on the basis of the (2+1)-flavor lattice QCD simulations close to the physical point ($m_{\pi }\simeq 146\mathrm{MeV}$ and $m_K\simeq 525\mathrm{MeV}$). Lattice QCD potentials in four different spin-isospin channels are extracted by using the coupled-channel HAL QCD method and are parametrized by analytic functions to calculate the scattering phase shifts. The $\Lambda \Lambda$ interaction at low energies shows only a weak attraction, which does not provide a bound or resonant dihyperon. The $N\Xi$ interaction in the spin-singlet and isospin-singlet channel is most attractive and lead the $N\Xi$ system near unitarity. Relevance to the strangeness=$-2$ hypernuclei as well as to two-baryon correlations in proton-proton, proton-nucleus and nucleus-nucleus collisions is also discussed.

    ↳ hep-lathep-phnucl-thNPA(2020)·174 citations
33. 33*

    Analytical relations for the bound state spectrum of gauge theories with a Brout-Englert-Higgs mechanism

    René Sondenheimer🇦🇹

    We apply the method proposed by Fröhlich, Morchio, and Strocchi to analyze the bound state spectrum of various gauge theories with a Brout-Englert-Higgs mechanism. These serve as building blocks for theories beyond the standard model but also stress the exceptional role of the standard model weak group. We will show how the Fröhlich-Morchio-Strocchi mechanism relates gauge-invariant bound state operators to invariant objects of the remaining unbroken gauge group after gauge fixing. In particular, this provides a strict gauge-invariant formulation of the latter in terms of the original gauge symmetry without using the terminology of spontaneous gauge symmetry breaking. We also demonstrate that the Fröhlich-Morchio-Strocchi approach allows us to put new constraints on theories beyond the standard model by pure field-theoretical considerations. Particularly the conventional construction of grand unified theories has to be rethought.

    ↳ hep-thhep-lathep-phPRD(2020)·31 citations
34. 34*

    Graduated dark energy: Observational hints of a spontaneous sign switch in the cosmological constant

    Ozgur Akarsu🇹🇷 · John D. Barrow🇬🇧 · Luis A. Escamilla🇲🇽 · J. Alberto Vazquez🇲🇽

    We study the cosmological constant ($\Lambda$) in the standard $\Lambda$CDM model by introducing the \textit{graduated dark energy} (gDE) characterised by a minimal dynamical deviation from the null inertial mass density of the $\Lambda$ in the form ${\rho }_{\mathrm{inert}}\propto {\rho }^{\lambda }<0$ with $\lambda <1$ being a ratio of two odd integers, for which its energy density $\rho$ dynamically takes negative values in the finite past. For large negative values of $\lambda$, it creates a phenomenological model described by a smooth function that approximately describes the $\Lambda$ spontaneously switching sign in the late universe to become positive today. We confront the model with the latest combined observational data sets of PLK+BAO+SN+$H$. It is striking that the data predict bimodal posterior probability distributions for the parameters of the model along with large negative $\lambda$ values; the new maximum significantly excludes the $\Lambda$, and the old maximum contains the $\Lambda$. The improvement in the goodness of fit for the $\Lambda$ reaches highly significant levels, $\Delta {\chi }_{\min }^2=6.4$ for the new maxima, while it remains at insignificant levels, $\Delta {\chi }_{\min }^2\lesssim 0.02$, for the old maxima. We show that, in contrast to the old maxima, which do not distinguish from the $\Lambda$, the new maxima agree with the model-independent $H_0$ measurements, high-precision Ly-$\alpha$ data, and model-independent $Om{h}^2$ diagnostic estimates. Our results provide strong hints of a spontaneous sign switch in the cosmological constant and lead us to conjecture that the universe has transitioned from AdS vacua to dS vacua, at a redshift $z\approx 2.32$ and triggered the late-time acceleration, and suggests looking for such mechanisms in string theory constructions.

    ↳ astro-ph.COgr-qchep-phhep-thPRD(2020)·197 citations
35. 35*

    Drag force to all orders in gradients

    Jared Reiten🇺🇸 · Andrey V. Sadofyev🇺🇸

    We study the energy loss of a heavy quark slowly moving through an evolving strongly coupled plasma. We use the linearized fluid/gravity correspondence to describe small perturbations of the medium flow with general spacetime dependence. This all order linearized hydrodynamics results in a drag force exerted on a heavy quark even when it is at rest with the fluid element. We show how the general contribution to the drag force can be derived order by order in the medium velocity gradients and provide explicit results valid up to the third order. We then obtain an approximate semi-analytic result for the drag force to all orders in the gradient expansion but linearized in the medium velocity. Thus, the effects of a class of hydrodynamic gradients on the drag force are re-summed, giving further insight into the dissipative properties of strongly coupled plasmas. The all order result allows us to study the drag force in the non-hydrodynamic regime of linear medium perturbations that vary rapidly in space and time.

    ↳ hep-thhep-phnucl-thJHEP(2020)·23 citations
36. 36*

    Renormalization Group Flows, the $a$-Theorem and Conformal Bootstrap

    Sandipan Kundu🇺🇸

    Every renormalization group flow in $d$ spacetime dimensions can be equivalently described as spectral deformations of a generalized free CFT in $(d-1)$ spacetime dimensions. This can be achieved by studying the effective action of the Nambu-Goldstone boson of broken conformal symmetry in anti-de Sitter space and then taking the flat space limit. This approach is particularly useful in even spacetime dimension where the change in the Euler anomaly $a_{UV}-a_{IR}$ can be related to anomalous dimensions of lowest twist multi-trace operators in the dual CFT. As an application, we provide a simple proof of the 4d $a$-theorem using the dual description. Furthermore, we reinterpret the statement of the $a$-theorem in 6d as a conformal bootstrap problem in 5d.

    ↳ hep-thgr-qchep-phquant-phJHEP(2020)·11 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.