Fri·Aug 16, 2019Friday·August 16, 2019

1. 01*

   Normalized symmetric cumulants as a measure of QCD phase transition: a viscous hydrodynamic study

   Ashutosh Dash🇮🇳 · Victor Roy🇮🇳

   Finding the existence and the location of the QCD critical point is one of the main goals of the RHIC beam energy scan program. To make theoretical predictions and corroborate with the experimental data requires modeling the space-time evolution of the matter created in heavy-ion collisions by dynamical models such as the relativistic hydrodynamics with an appropriate Equation of State (EoS). In the present exploratory study, we use a viscous 2+1 dimensional event-by-event (e-by-e) hydrodynamic code at finite baryon densities with two different EoSs (i) Lattice QCD + HRG with a crossover transition and (ii) EoS with a first-order phase transition to studying the normalized symmetric cumulants of charged pions $v_n$ $(n=2-4)$. We show that the normalized symmetric cumulants can differentiate the two EoSs while all other conditions remain the same. The conclusion does not change for various initial conditions and shear viscosity. This indicates that these observables can be used to gain information about the QCD EoS from experimental data and can be used as an EoS meter.

   hep-phnucl-th2 citations
2. 02*

   Low-energy effective field theory below the electroweak scale: matching at one loop

   Wouter Dekens🇺🇸 · Peter Stoffer🇺🇸

   We compute the one-loop matching between the Standard Model Effective Field Theory and the low-energy effective field theory below the electroweak scale, where the heavy gauge bosons, the Higgs particle, and the top quark are integrated out. The complete set of matching equations is derived including effects up to dimension six in the power counting of both theories. We present the results for general flavor structures and include both the $CP$-even and $CP$-odd sectors. The matching equations express the masses, gauge couplings, as well as the coefficients of dipole, three-gluon, and four-fermion operators in the low-energy theory in terms of the parameters of the Standard Model Effective Field Theory. Using momentum insertion, we also obtain the matching for the $CP$-violating theta angles. Our results provide an ingredient for a model-independent analysis of constraints on physics beyond the Standard Model. They can be used for fixed-order calculations at one-loop accuracy and represent a first step towards a systematic next-to-leading-log analysis.

   hep-phJHEP(2019)·209 citations
3. 03*

   Strong decays of the latest LHCb pentaquark candidates in hadronic molecule pictures

   Yong-Hui Lin🇨🇳 · Bing-Song Zou🇨🇳

   We investigate the observed pentaquark candidates $P_c(4312)$, $P_c(4440)$ and $P_c(4457)$ from the latest LHCb measurement, as well as four possible spin partners in the ${\bar{D}}^{(\ast )}{\Sigma }_c^{\ast }$ system predicted from the heavy quark spin symmetry with the hadronic molecule scenarios. Similar to the previous calculation on $P_c(4380)$ and $P_c(4450)$, the partial widths of all the allowed decay channels for these $P_c$ states are estimated with the effective Lagrangian method. The cutoff dependence of our numerical results are also presented. Comparing with the experimental widths, our results show that $P_c(4312)$, $P_c(4440)$ and $P_c(4457)$ can be described well with the spin-parity-$1/2^{-}$-$\bar{D}{\Sigma }_c$, $1/2^{-}$-${\bar{D}}^{\ast }{\Sigma }_c$ and $3/2^{-}$-${\bar{D}}^{\ast }{\Sigma }_c$ molecule pictures, respectively.

   hep-phnucl-thPRD(2019)·108 citations
4. 04*

   $b\bar{b}$ Kinematic Correlations in Cold Nuclear Matter

   R. Vogt🇺🇸

   Background: The LHCb Collaboration has studied a number of kinematic correlations between $B$-hadron pairs through their subsequent decays to $J/\psi$ pairs at 7 and 8 TeV for four minimum values of the $J/\psi$ $p_T$. Purpose: In this work, these measurements are compared to calculations of $b\bar{b}$ pairs and their hadronization and inclusive decays to $J/\psi J/\psi$ are compared to the same observables. Potential cold matter effects on the $b\bar{b}$ pair observables are discussed to determine which are most likely to provide insights about the system and why. Methods: The calculations, employing the exclusive HVQMNR code, assume the same intrinsic $k_T$-broadening and fragmentation as in [R. Vogt, Phys. Rev. C {\bf 98} (2018) 034907]. The pair distributions presented by LHCb are calculated in this approach, both for the parent $b\bar{b}$ and the $J/\psi J/\psi$ pairs produced in their decay. The sensitivity of the results to the intrinsic $k_T$ broadening is shown. The theoretical uncertainties due to the $b$ quark mass and scale variations on both the initial $b\bar{b}$ pairs and the resulting $J/\psi$ pairs are also shown. Possible effects due to the presence of the nucleus are studied by increasing the size of the $k_T$ broadening and modification of the fragmentation parameter. Results: Good agreement with the LHCb data is found for all observables. The parent $b\bar{b}$ distributions are more sensitive to the $k_T$ broadening than are the final-state $J/\psi$ pairs. Conclusions: Next-to-leading order calculations with $k_T$ broadening, as in [R. Vogt, Phys. Rev. C {\bf 98} (2018) 034907], can describe all correlated observables. Multiple measurements of correlated observables are sensitive to different nuclear effects which can help distinguish between them.

   hep-phPRC(2020)·16 citations
5. 05*

   Dimesoatom breakup in the Coulomb field

   L.G. Afanasyev🇷🇺 · S.R. Gevorkyan🇷🇺 · O.O. Voskresenskaya🇷🇺

   Momentum and angular distributions of charged meson pairs $h^{+}{h}^{-}$ ($h=\pi ,K$) from elementary atoms (EA) breakup (ionization) in the Coulomb field of a target atom is considered in the Born and Glauber approximations. Exploiting the fact that the atomic screening of the target Coulomb potential is important at small transfer momenta, while multi-photon exchanges are essential at large transfer momenta we express the cross sections of EA breakup as a sum of two terms. In the region of modest transfer momenta the cross section is determined by the single-photon exchange (first Born approximation) accounting for the target atoms screening, whereas at large transfer momenta using the unscreened potential allows to take into account all multi-photon exchanges and obtain the cross section of EA breakup in the close analytical form.

   hep-phEPJA(2020)·0 citations
6. 06*

   The method of mixed events for higher cumulants of conserved charges

   Fan Zhang🇨🇳 · Zhiming Li🇨🇳 · Lizhu Chen🇨🇳 · Xue Pan🇨🇳 · Mingmei Xu🇨🇳 · Yeyin Zhao🇨🇳 · Yu Zhou🇺🇸 · Yuanfang Wu🇨🇳

   Higher cumulants of conserved charges are sensitive observables of quantum chromodynamics phase transitions. The sample of mixed events provides a background to estimate non-critical effects of cumulants. Four possible methods for constructing the sample of mixed events are suggested. The effectiveness of each method is examined. It is showed that the method of most random or least constrain is the best, rather than the conventional method.

   hep-ph2 citations
7. 07*

   Subtracting non-critical fluctuations in higher cumulants of conserved charges

   Fan Zhang🇨🇳 · Zhiming Li🇨🇳 · Lizhu Chen🇨🇳 · Xue Pan🇨🇳 · Mingmei Xu🇨🇳 · Yeyin Zhao🇨🇳 · Yu Zhou🇺🇸 · Yuanfang Wu🇨🇳

   Using the sample produced by the AMPT default model, we construct a corresponding mixed sample by the method of mixed events. The mixed sample provides an effective estimation for non-critical fluctuations which are caused by global and systematic effects. The dynamical cumulants of conserved charges are defined as the cumulants of the original sample minus the cumulants of the mixed sample. It is demonstrated that dynamical cumulants are subtracted statistical fluctuations, and centrality bin width or detection efficiency independent, in consistent with formulae corrected cumulants. Therefore, dynamical cumulants are helpful in obtaining critical fluctuations at the RHIC BES.

   hep-ph1 citation
8. 08*

   Chaotic inflation with four-form couplings

   Hyun Min Lee🇰🇷

   We consider chaotic inflation models with a pseudo-scalar field containing the general couplings to the four-form flux. The four-form mixing with the pseudo-scalar field induces a quadratic potential for inflaton while the coexisting four-form mixing with graviton generates a non-minimal gravity coupling for inflaton. The shift symmetry is respected by the derived inflaton couplings and it is broken spontaneously only by the fixed four-form flux. We discuss the success of inflationary predictions and robustness against higher order terms. Finally, the built-in reheating mechanism is also addressed.

   hep-phPRD(2020)·7 citations
9. 09*

   Relativistic Freeze-in

   Oleg Lebedev🇫🇮 · Takashi Toma🇨🇦

   We study production of scalar dark matter via the freeze--in mechanism in the relativistic regime, focussing on the simplest Higgs portal model. We derive the corresponding relativistic reaction rates based on the Bose--Einstein statistics taking into account the thermal mass effects as well as the change in the Higgs degrees of freedom at the electroweak phase transition. The consequent constraints on the Higgs portal coupling are obtained.

   hep-phPLB(2019)·63 citations
10. 10*

    Effective field theory and scalar extensions of the top quark sector

    Christoph Englert🇬🇧 · Peter Galler🇬🇧 · Chris D. White🇬🇧

    Effective field theory (EFT) approaches are widely used at the LHC, such that it is important to study their validity, and ease of matching to specific new physics models. In this paper, we consider an extension of the SM in which a top quark couples to a new heavy scalar. We find the dimension six operators generated by this theory at low energy, and match the EFT to the full theory up to NLO precision in the simplified model coupling. We then examine the range of validity of the EFT description in top pair production, finding excellent validity even if the scalar mass is only slightly above LHC energies, provided NLO corrections are included. In the absence of the latter, the LO EFT overestimates kinematic distributions, such that over-optimistic constraints on BSM contributions are obtained. We next examine the constraints on the EFT and full models that are expected to be obtained from both top pair and four top production at the LHC, finding for low scalar masses that both processes show similar exclusion power. However, for larger masses, estimated LHC uncertainties push constraints into the non-perturbative regime, where the full model is difficult to analyse, and thus not perturbatively matchable to the EFT. This highlights the necessity to improve uncertainties of SM hypotheses in top final states.

    hep-phhep-exPRD(2020)·21 citations
11. 11*

    A new parton model for the soft interactions at high energies: two channel approximation

    E. Gotsman (Tel Aviv U.)🇮🇱 · E. Levin (Tel AvivU./UTFSM)🇮🇱 · I. Potashnikova (UTFSM)🇨🇱

    The primary goal of this paper is to describe the diffraction production using the model that takes into account the Pomeron interaction, and satisfies both $t$ and $s$ channel unitarity. We hope that these features will allow us to describe the diffraction production in a more convenient way than in CGC motivated models, that do not satisfy these unitarity constraints. Unfortunately, we show that both approaches are only able to describe half of the cross section for the single diffraction production, leaving the second half to be estimate of the large mass production in the Pomeron approach.The impact parameter dependance of the scattering amplitudes show that soft interactions at high energies measured at the LHC, have a much richer structure than presumed. We discuss the $t$-dependence of the elastic cross section in wide range of $|t|=0÷1Ge{V}^2$. We show that in the kinemati region of the minimum, we cannot use approximate formulae to calculate the real part of the amplitude. The exact calculation in our model, shows that the real part is rather small, and it is necessary to include the Odderon contribution in order to describe the experimental data.

    hep-phhep-ex3 citations
12. 12*

    Forbidden frozen-in dark matter

    Luc Darmé🇵🇱 · Andrzej Hryczuk🇵🇱 · Dimitrios Karamitros🇵🇱 · Leszek Roszkowski🇵🇱

    We examine and point out the importance of a regime of dark matter production through the freeze-in mechanism that results from a large thermal correction to a decaying mediator particle mass from hot plasma in the early Universe. We show that mediator decays to dark matter that are kinematically forbidden at the usually considered ranges of low temperatures can be generically present at higher temperatures and actually dominate the overall dark matter production, thus leading to very distinct solutions from the standard case. We illustrate these features by considering a dark Higgs portal model where dark matter is produced via decays of a scalar field with a large thermal mass. We identify the resulting ranges of parameters that are consistent with the correct dark matter relic abundance and further apply current and expected future collider, cosmological, and astrophysical limits.

    hep-phJHEP(2019)·35 citations
13. 13*

    Critical look at the time-energy uncertainty relations

    K. Urbanowski🇵🇱

    The Heisenberg and Mandelstam-Tamm time-energy uncertainty relations are analyzed. The conlusion resulting from this analysis is that within the Quantum Mechanics of Schrödinger and von Neumann, the status of these relations can not be considered as the same as the status of the position-momentum uncertainty relations, which are rigorous. The conclusion is that the time--energy uncertainty relations can not be considered as universally valid.

    ↳ quant-phhep-phphysics.pop-phActa Phys.Polon.B(2020)·0 citations
14. 14*

    Prospects and Limitations for Constraining Light Relics with Primordial Abundance Measurements

    Alex Laguë🇨🇦 · Joel Meyers🇨🇦

    The light relic density affects the thermal and expansion history of the early Universe leaving a number of observable imprints. We focus on the primordial abundances of light elements produced during the process of Big Bang nucleosynthesis which are influenced by the light relic density. Primordial abundances can be used to infer the density of light relics and thereby serve as a probe of physics beyond the Standard Model. We calculate the observational uncertainty on primordial light element abundances and associated quantities that would be required in order for these measurements to achieve sensitivity to the light relic density comparable to that anticipated from upcoming cosmic microwave background surveys. We identify the nuclear reaction rates that need to be better measured to maximize the utility of future observations. We show that improved measurements of the primordial helium-4 abundance can improve constraints on light relics, while more precise measurements of the primordial deuterium abundance are unlikely to be competitive with cosmic microwave background measurements of the light relic density.

    ↳ astro-ph.COhep-phPRD(2020)·13 citations
15. 15*

    JEDI-net: a jet identification algorithm based on interaction networks

    Eric A. Moreno🇺🇸 · Olmo Cerri🇺🇸 · Javier M. Duarte🇺🇸 · Harvey B. Newman🇺🇸 · Thong Q. Nguyen🇺🇸 · Avikar Periwal🇺🇸 · Maurizio Pierini🇨🇭 · Aidana Serikova🇺🇸 · Maria Spiropulu🇺🇸 · Jean-Roch Vlimant🇺🇸

    We investigate the performance of a jet identification algorithm based on interaction networks (JEDI-net) to identify all-hadronic decays of high-momentum heavy particles produced at the LHC and distinguish them from ordinary jets originating from the hadronization of quarks and gluons. The jet dynamics are described as a set of one-to-one interactions between the jet constituents. Based on a representation learned from these interactions, the jet is associated to one of the considered categories. Unlike other architectures, the JEDI-net models achieve their performance without special handling of the sparse input jet representation, extensive pre-processing, particle ordering, or specific assumptions regarding the underlying detector geometry. The presented models give better results with less model parameters, offering interesting prospects for LHC applications.

    ↳ hep-exhep-phEPJC(2020)·176 citations
16. 16*

    Probing $\Omega \Omega$ and $p\Omega$ dibaryons with femtoscopic correlations in relativistic heavy-ion collisions

    Kenji Morita🇯🇵 · Shinya Gongyo🇯🇵 · Tetsuo Hatsuda🇯🇵 · Tetsuo Hyodo🇯🇵 · Yuki Kamiya🇨🇳 · Akira Ohnishi🇯🇵

    The momentum correlation functions of baryon pairs, which reflects the baryon-baryon interaction at low energies, are investigated for multi-strangeness pairs ($\Omega \Omega$ and $N\Omega$) produced in relativistic heavy-ion collisions. We calculate the correlation functions based on an expanding source model constrained by single-particle distributions. The interaction potentials are taken from those obtained from recent lattice QCD calculations at nearly physical quark masses. Experimental measurements of these correlation functions for different system sizes will help to disentangle the strong interaction between baryons and to unravel the possible existence of strange dibaryons.

    ↳ nucl-thhep-lathep-phnucl-exPRC(2020)·80 citations
17. 17*

    Ab Initio Treatment of Collective Correlations and the Neutrinoless Double Beta Decay of ${}^{48}$Ca

    J. M. Yao🇺🇸 · B. Bally🇺🇸 · J. Engel🇺🇸 · R. Wirth🇺🇸 · T. R. Rodríguez🇪🇸 · H. Hergert🇺🇸

    Working with Hamiltonians from chiral effective field theory, we develop a novel framework for describing arbitrary deformed medium-mass nuclei by combining the in-medium similarity renormalization group with the generator coordinate method. The approach leverages the ability of the first method to capture dynamic correlations and the second to include collective correlations without violating symmetries. We use our scheme to compute the matrix element that governs the neutrinoless double beta decay of ${}^{48}$Ca to ${}^{48}$Ti, and find it to have the value $0.61$, near or below the predictions of most phenomenological methods. The result opens the door to ab initio calculations of the matrix elements for the decay of heavier nuclei such as ${}^{76}$Ge, ${}^{130}$Te, and ${}^{136}$Xe.

    ↳ nucl-thhep-phnucl-exPRL(2020)·195 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.