Thu·Sep 20, 2018Thursday·September 20, 2018

1. 01*

   On the direct detection of multi-component dark matter: implications of the relic abundance

   Juan Herrero-Garcia🇦🇺 · Andre Scaffidi🇦🇺 · Martin White🇦🇺 · Anthony G. Williams🇦🇺

   Recently we studied the direct detection of multi-component dark matter with arbitrary local energy densities. Although the generation of the dark matter relic abundance is model-dependent, and in principle could be only indirectly related to direct detection, it is interesting to consider the implications of the former on the latter. In this work we conduct an extended analysis to include constraints from two natural scenarios of dark matter genesis: asymmetric dark matter and thermal freeze-out. In the first (second) case, the dark matter number (energy) densities of the different components are expected to be similar. In the case of thermal freeze-out, we assume that the global energy density scales with the local one. In our numerical analysis we analyse the median sensitivity of direct detection experiments to discriminate a two-component scenario from a one-component one, and also the precision with which dark matter parameters can be extracted. We analyse these generic scenarios for both light and heavy mediators. We find that most scenarios have a relatively suppressed maximum median sensitivity compared to the previously studied general cases. We also find that the asymmetric scenario is more promising than the thermal freeze-out one.

   hep-phJCAP(2019)·34 citations
2. 02*

   Flavor symmetry breaking in the $\Delta$ sea

   J. J. Ethier🇳🇱 · W. Melnitchouk🇺🇸 · Fernanda Steffens🇩🇪 · A. W. Thomas🇦🇺

   The discovery of a sizeable asymmetry in the $\bar{u}$ and $\bar{d}$ distributions in the proton was one of the more consequential experimental findings in hadron physics last century. Although widely believed to be related to the fundamental role of chiral symmetry in QCD, a definitive verification of this hypothesis has remained elusive. We propose a novel test of the role of chiral symmetry in generating the sea flavor asymmetry by comparing the $\bar{d}-\bar{u}$ content in the proton with that in the ${\Delta }^{+}$ baryon, where a significant enhancement is expected around the opening of the $N\pi$ decay channel. Recent developments in lattice QCD suggest a promising way to test this prediction in the near future.

   hep-phhep-latnucl-thPRD(2019)·4 citations
3. 03*

   Considerations on the Schmid theorem for triangle singularities

   V. R. Debastiani🇪🇸 · S. Sakai🇪🇸 · E. Oset🇪🇸

   We investigate the Schmid theorem, which states that if one has a tree level mechanism with a particle decaying to two particles and one of them decaying posteriorly to two other particles, the possible triangle singularity developed by the mechanism of elastic rescattering of two of the three decay particles does not change the cross section provided by the tree level. We investigate the process in terms of the width of the unstable particle produced in the first decay and determine the limits of validity and violation of the theorem. One of the conclusions is that the theorem holds in the strict limit of zero width of that resonance, in which case the strength of the triangle diagram becomes negligible compared to the tree level. Another conclusion, on the practical side, is that for realistic values of the width, the triangle singularity can provide a strength comparable or even bigger than the tree level, which indicates that invoking the Schmid theorem to neglect the triangle diagram stemming from elastic rescattering of the tree level should not be done. Even then, we observe that the realistic case keeps some memory of the Schmid theorem, which is visible in a peculiar interference pattern with the tree level.

   hep-phEPJC(2019)·36 citations
4. 04*

   Transient and pre-transient stages in field induced phase transition of vacuum state

   Chitradip Banerjee🇮🇳 · Manoranjan P. Singh🇮🇳

   Evolution of modulus and phase of complex order parameter associated with field induced phase transition (FIPT) of the vacuum state interacting with time dependent Sauter pulse is studied to analyse different evolution stages of the order parameter e.g., quasi electron positron plasma (QEPP), transient, and residual electron-positron plasma (REPP) stages. By revisiting FIPT in presence of single-sheeted and multi-sheeted pulses, we attribute the transient stage to the nonlinear coupling in the differential equations governing the dynamics of the phase and the modulus of the order parameter. The appearance of the rapid oscillations in the modulus is shown to be associated with the abrupt change in the phase of the order parameter in the transient stage. FIPT is also studied for multi-sheeted Sauter pulse with linear and quadratic frequency chirp. QEEP stage is found to show complex dynamical behaviour with fast and irregular oscillations due to the frequency chirp. The formation of pre-transient region due to the quadratic frequency chirping is observed in the accelerating part of the QEPP stage before the electric field attains the maximum value. As the quadratic chirp is increased the pre-transient and transient stages move closer to the electric field maximum which leads to a decrease in temporal separation between the two stages. The early appearance of the transient stage and hence of the following REPP stage results in the enhancement of pair production rate.

   hep-phPRD(2019)·6 citations
5. 05*

   Heavy mesons in the Quark Model

   D.R. Entem🇪🇸 · P.G. Ortega🇪🇸 · J. Segovia🇪🇸 · F. Fernández🇪🇸

   Since the discovery of the $J/\psi$, the quark model was very successful in describing the spectrum and properties of heavy mesons including only $q\bar{q}$ components. However since 2003, with the discovery of the $X(3872)$, many states that can not be accommodated on the naive quark model have been discovered, and they made unavoidable to include higher Fock components on the heavy meson states. We will give an overview of the success of the quark model for heavy mesons and point some of the states that are likely to be more complicated structures such as meson-meson molecules.

   hep-phEPJ Web Conf.(2019)·1 citation
6. 06*

   Effect of external magnetic field on nucleon mass in hot and dense medium : Inverse Magnetic Catalysis in Walecka Model

   Arghya Mukherjee🇮🇳 · Snigdha Ghosh🇮🇳 · Mahatsab Mandal🇮🇳 · Sourav Sarkar🇮🇳 · Pradip Roy🇮🇳

   Vacuum to nuclear matter phase transition has been studied in presence of constant external background magnetic field with the mean field approximation in Walecka model. The anomalous nucleon magnetic moment has been taken into account using the modified "weak" field expansion of the fermion propagator having non-trivial correction terms for charged as well as for neutral particles. The effect of nucleon magnetic moment is found to favour the magnetic catalysis effect at zero temperature and zero baryon density. However, extending the study to finite temperatures, it is observed that the anomalous nuclear magnetic moment plays a crucial role in characterizing the qualitative behaviour of vacuum to nuclear matter phase transition even in case of the weak external magnetic fields . The critical temperature corresponding to the vacuum to nuclear medium phase transition is observed to decrease with the external magnetic field which can be identified as the inverse magnetic catalysis in Walecka model whereas the opposite behaviour is obtained in case of vanishing magnetic moment indicating magnetic catalysis.

   hep-phPRD(2018)·47 citations
7. 07*

   Up- and down-quark masses from QCD sum rules

   C. A. Dominguez🇿🇦 · A. Mes🇿🇦 · K. Schilcher🇿🇦

   The QCD up- and down-quark masses are determined from an optimized QCD Finite Energy Sum Rule (FESR) involving the correlator of axial-vector current divergences. In the QCD sector this correlator is known to five loop order in perturbative QCD (PQCD), together with non-perturbative corrections from the quark and gluon condensates. This FESR is designed to reduce considerably the systematic uncertainties arising from the hadronic spectral function. The determination is done in the framework of both fixed order and contour improved perturbation theory. Results from the latter, involving far less systematic uncertainties, are: ${\bar{m}}_u(2\text{mbox}GeV)=(2.6\pm 0.4)\text{mbox}MeV$, ${\bar{m}}_d(2\text{mbox}GeV)=(5.3\pm 0.4)\text{mbox}MeV$, and the sum ${\bar{m}}_{ud}\equiv ({\bar{m}}_u+{\bar{m}}_d)/2$, is ${\bar{m}}_{ud}(2\text{mbox}GeV)=(3.9\pm 0.3)\text{mbox}MeV$.

   hep-phhep-latJHEP(2019)·12 citations
8. 08*

   Numerical Implementation of Harmonic Polylogarithms to Weight w = 8

   J. Ablinger🇦🇹 · J. Blümlein🇩🇪 · M. Round🇦🇹 · C. Schneider🇦🇹

   We present the FORTRAN-code HPOLY.f for the numerical calculation of harmonic polylogarithms up to w = 8 at an absolute accuracy of $\sim 4.9\cdot 10^{-15}$ or better. Using algebraic and argument relations the numerical representation can be limited to the range $x\in [0,\sqrt{2}-1]$. We provide replacement files to map all harmonic polylogarithms to a basis and the usual range of arguments $x\in ]-\infty ,+\infty [$ to the above interval analytically. We also briefly comment on a numerical implementation of real valued cyclotomic harmonic polylogarithms.

   hep-phhep-thmath-phmath.MPComput.Phys.Commun.(2019)·59 citations
9. 09*

   Enhancing $CP$ Measurement of the Yukawa Interactions of Top-Quark at $e^{-}{e}^{+}$ Collider

   Kai Ma🇨🇳

   It is well known that $CP$-violating coupling of the Yukawa interaction of top-quark is a promising candidate of a new source of $CP$ violation effect. Precisely measurement of its $CP$ properties is crucial for understanding new physics above the electroweak scale. In this paper, we introduce a complete analysis method for probing $CP$ violation effects in the associated production of top-quark pair and Higgs boson at $e^{-}{e}^{+}$ collider. Reconstructions of the top-quarks are not needed in our strategy. The observables are defined based on spin correlation effects of the leptons emerging from decays of top-quarks, and their formal expressions are universal at any reference frames. Two reference frames, the rest frame of the top-quark pair and the rest frame of Higgs boson, are examined. Importantly, large enhancement effects for both $CP$-odd and $CP$-even observables are observed in the rest frame of Higgs boson. This can be essential for probing $CP$ violation effects at future $e^{-}{e}^{+}$ collider.

   hep-phhep-exPLB(2019)·12 citations
10. 10*

    Looking for non-perturbative effects of the electroweak interaction at the LHC

    B.A. Arbuzov🇷🇺 · I.V. Zaitsev🇷🇺

    We are considering a possibility for detecting non-perturbative effect in process of top pair production in association with a high $p_T$ photon. Starting from previous results on two solutions for a spontaneous generation of wouldbe effective interaction of a top pair with a pair of electro-weak bosons, we show, that a solution with effective cut-off $\Lambda \simeq 10^{2}TeV$ is already contradicting to existing data, while the other one with $\Lambda \simeq 10^{16}TeV$ (just the Planck scale) could be reconciled with data and give predictions for process $p+p\to \bar{t}t\gamma +X$, which could be effectively checked at the LHC with $\sqrt{s}=13TeV$. The confirmation of the predictions would mean a strong support for the existence of non-perturbative effects in the electro-weak interaction.

    hep-phhep-exInt.J.Mod.Phys.A(2019)·0 citations
11. 11*

    Hidden-Beauty Broad Resonance $Y_b(10890)$ in Thermal QCD

    J.Y. Süngü🇹🇷 · A. Türkan🇹🇷 · H. Dağ🇹🇷 · E. Veli Veliev🇹🇷

    In this work, the mass and pole residue of resonance $Y_b$ is studied by using QCD sum rules approach at finite temperature. Resonance $Y_b$ is described by a diquark-antidiquark tetraquark current, and contributions to operator product expansion are calculated by including QCD condensates up to dimension six. Temperature dependences of the mass $m_{Y_b}$ and the pole residue ${\lambda }_{Y_b}$ are investigated. It is seen that near a critical temperature $(T_c\simeq 190\mathrm{MeV})$, the values of $m_{Y_b}$ and ${\lambda }_{Y_b}$ are decreased to $87\%$, and to $44\%$ of their values at vacuum.

    hep-phAdv.High Energy Phys.(2019)·5 citations
12. 12*

    Boosting the $H\to$ invisibles searches with $Z$ boson polarization

    Dorival Goncalves🇺🇸 · Junya Nakamura🇩🇪

    It is argued that, in $H\to$ invisibles searches with $Z(\ell \ell )H$ associated production at the LHC, the signal efficiency can be sensibly improved via a detailed study of the $Z$ boson polarization, discriminating between the signal and the dominant-irreducible $Z(\ell \ell )Z(\nu \nu )$ background. We first present a comprehensive polarization study, obtaining the complete set of angular coefficients $A_i$ in the Collins-Soper reference frame and identifying the dominant phenomenological effects. Then, we show the results for a realistic Monte Carlo study to $H\to$ invisibles, taking the polarization analysis into account. We obtain about $20\%$ improvement in the upper bound for the branching ratio of the Higgs boson to invisible particles, assuming $300{\mathrm{fb}}^{-1}$ of data at the 13 TeV LHC.

    hep-phhep-exPRD(2019)·23 citations
13. 13*

    Detecting a Boosted Diboson Resonance

    Kaustubh Agashe🇺🇸 · Jack H. Collins🇺🇸 · Peizhi Du🇺🇸 · Sungwoo Hong🇺🇸 · Doojin Kim🇨🇭 · Rashmish K. Mishra🇮🇹

    New light scalar particles in the mass range of hundreds of GeV, decaying into a pair of $W/Z$ bosons can appear in several extensions of the SM. The focus of collider studies for such a scalar is often on its direct production, where the scalar is typically only mildly boosted. The observed $W/Z$ are therefore well-separated, allowing analyses for the scalar resonance in a standard fashion as a low-mass diboson resonance. In this work we instead focus on the scenario where the direct production of the scalar is suppressed, and it is rather produced via the decay of a significantly heavier (a few TeV mass) new particle, in conjunction with SM particles. Such a process results in the scalar being highly boosted, rendering the $W/Z$'s from its decay merged. The final state in such a decay is a "fat" jet, which can be either four-pronged (for fully hadronic $W/Z$ decays), or may be like a $W/Z$ jet, but with leptons buried inside (if one of the $W/Z$ decays leptonically). In addition, this fat jet has a jet mass that can be quite different from that of the $W/Z$/Higgs/top quark-induced jet, and may be missed by existing searches. In this work, we develop dedicated algorithms for tagging such multi-layered "boosted dibosons" at the LHC. As a concrete application, we discuss an extension of the standard warped extra-dimensional framework where such a light scalar can arise. We demonstrate that the use of these algorithms gives sensitivity in mass ranges that are otherwise poorly constrained.

    hep-phJHEP(2018)·26 citations
14. 14*

    Inflating to the Weak Scale

    Michael Geller🇺🇸 · Yonit Hochberg🇮🇱 · Eric Kuflik🇮🇱

    We present a new solution to the hierarchy problem, where the Higgs mass is at its observed electroweak value because such a patch inflates the most in the early universe. If the Higgs mass depends on a field undergoing quantum fluctuations during inflation, then inflation will fill the universe with the Higgs mass that corresponds to the largest vacuum energy. The hierarchy problem is solved if the maximum vacuum energy occurs for the observed Higgs mass. We demonstrate this notion with a proof-of-principle model containing an axion, a modulus field and the Higgs, and show that inflation can be responsible for the weak scale.

    hep-phhep-thPRL(2019)·55 citations
15. 15*

    Cosmological Aspects of Higgs Vacuum Metastability

    Tommi Markkanen🇬🇧 · Arttu Rajantie🇬🇧 · Stephen Stopyra🇬🇧

    The current central experimental values of the parameters of the Standard Model give rise to a striking conclusion: metastability of the electroweak vacuum is favoured over absolute stability. A metastable vacuum for the Higgs boson implies that it is possible, and in fact inevitable, that a vacuum decay takes place with catastrophic consequences for the Universe. The metastability of the Higgs vacuum is especially significant for cosmology, because there are many mechanisms that could have triggered the decay of the electroweak vacuum in the early Universe. We present a comprehensive review of the implications from Higgs vacuum metastability for cosmology along with a pedagogical discussion of the related theoretical topics, including renormalization group improvement, quantum field theory in curved spacetime and vacuum decay in field theory.

    ↳ astro-ph.COhep-phhep-thFront.Astron.Space Sci.(2018)·170 citations
16. 16*

    Consistency of Modified Gravity with a decreasing $G_{\mathrm{eff}}(z)$ in a $\Lambda$CDM background

    Radouane Gannouji🇨🇱 · Lavrentios Kazantzidis🇬🇷 · Leandros Perivolaropoulos🇬🇷 · David Polarski🇫🇷

    Recent analyses \cite{Nesseris:2017vor,Kazantzidis:2018rnb} have indicated that an effective Newton's constant $G_{\mathrm{eff}}(z)$ decreasing with redshift may relieve the observed tension between the Planck15 best fit $\Lambda$CDM cosmological background ({\it i.e.} Planck15/$\Lambda$CDM) and the corresponding $\Lambda$CDM background favored by growth $f{\sigma }_8$ and weak lensing data. We investigate the consistency of such a decreasing $G_{\mathrm{eff}}(z)$ with some viable scalar-tensor models and $f(R)$ theories. We stress that $f(R)$ theories generically can not lead to a decreasing $G_{\mathrm{eff}}(z)$ for any cosmological background. For scalar-tensor models we deduce that in the context of a $\Lambda$CDM cosmological background, a decreasing $G_{\mathrm{eff}}(z)$ is not consistent with a large Brans-Dicke parameter ${\omega }_{BD,0}$ today. This inconsistency remains and amplifies in the presence of a phantom dark energy equation of state parameter ($w<-1$). However it can be avoided for $w>-1$. We also find that any modified gravity model with the required decreasing $G_{\mathrm{eff}}(z)$ and $G_{\mathrm{eff},0}=G$, would have a characteristic signature in its growth index $\gamma$ with $0.61\lesssim {\gamma }_0\lesssim 0.69$ and large slopes ${\gamma }_0^{\prime }$, $0.16\lesssim {\gamma }_0^{\prime }\lesssim 0.4$, which is a characteristic signature of a decreasing (with $z$) $G_{\mathrm{eff}}(z)<G$ on small redshifts. This is a substantial departure today from the quasi-static behaviour in $\Lambda$CDM with $({\gamma }_0,{\gamma }_0^{\prime })\approx (0.55,-0.02)$.

    ↳ gr-qcastro-ph.COhep-phhep-thPRD(2018)·38 citations
17. 17*

    Dilepton Radiation in Heavy-Ion Collisions at Small Transverse Momentum

    Mariola Klusek-Gawenda🇵🇱 · Ralf Rapp🇺🇸 · Wolfgang Schäfer🇵🇱 · Antoni Szczurek🇵🇱

    We study the invariant-mass distributions of dileptons produced in ultrarelativistic heavy-ion collisions at very low pair transverse momenta, $P_T\le 0.15$ GeV. Specifically, we investigate the interplay of thermal radiation with initial photon annihilation processes, $\gamma \gamma \to l^{+}{l}^{-}$, triggered by the coherent electromagnetic fields of the incoming nuclei. For the thermal radiation, we employ the emission from the QGP and hadronic phases with in-medium vector spectral functions which describes the inclusive excess radiation observed over a wide range of collision energies. For the coherent photon fusion processes, whose spectrum is much softer than for thermal radiation, we employ initial fluxes from the Fourier transform of charge distributions of the colliding nuclei in the equivalent-photon approximation. We first verify that the combination of photon fusion, thermal radiation and final-state hadron decays gives a fair description of the low-$P_T$ dilepton mass spectra as recently measured by the STAR collaboration in $\sqrt{s_{NN}}$=200 GeV Au+Au collisions for different centrality classes, including experimental acceptance cuts. The coherent contribution dominates in peripheral collisions, while thermal radiation shows a markedly stronger increase with centrality. We perform similar calculations at lower collision energies ($\sqrt{s_{NN}}$=17.3 GeV) and compare to the acceptance-corrected dimuon excess spectra measured by the NA60 experiment at the CERN SPS; here, the contribution from photoproduction is subleading. We also provide predictions for the ALICE experiment at the LHC; the pertinent excitation function from SPS to LHC energies reveals a nontrivial interplay of photoproduction and thermal radiation.

    ↳ nucl-thhep-phPLB(2019)·44 citations
18. 18*

    Quasiparticle properties of nonequilibrium gluon plasma

    Jarkko Peuron🇫🇮

    We apply classical gluodynamics to early stages of ultrarelativistic heavy-ion collisions. We start by going through the space-time evolution of ultrarelativistic heavy-ion collisions in the color glass condensate framework and the basics of real-time gluodynamics on the lattice in the temporal gauge. We study the plasmon mass scale in three- and two-dimensional systems by comparing three different methods to measure the mass scale. The methods are a formula which can be derived from Hard Thermal Loop effective theory at leading order (HTL), the effective dispersion relation (DR) and measurement of the plasma oscillation frequency triggered by the introduction of a uniform electric field (UE) into the system. We observe that in both systems the plasmon mass scale decreases like a power law after an occupation number dependent initial transient time. In both cases the UE and HTL methods are in rough agreement, and in the three-dimensional case the two agree in the continuum limit. As a second way to study the quasiparticle properties, we derive, implement and test an algorithm which can be used to simulate linearized fluctuations on top of the classical background. The algorithm is derived by requiring conservation of Gauss' law and gauge invariance. We then apply the algorithm to spectral properties of overoccupied gluodynamics using linear response theory. We establish the existence of transverse and longitudinal quasiparticles by extracting their spectral functions. We also extract the dispersion relation, effective mass, plasmon mass and damping rate of the quasiparticles. Our results are consistent with the HTL effective theory, but we also observe effects beyond leading order HTL.

    ↳ hep-lathep-phnucl-th1 citation
19. 19*

    A cross-validation check in the covariance analysis of isospin sensitive observables from heavy ion collision

    Ilona Bednarek🇵🇱 · Jacek Syska🇵🇱 · Jan Sładkowski

    This paper focuses on two problems. The first is related to the consistency checks of the complete correlation coefficients between two groups of variables obtained in Phys. Lett. B 749, 262 (2015). The first group collects parameters that describe properties of nuclear matter referring to the transport model involved. The second one is a group of observables adopted in the heavy ion collision experiments. The second problem concerns the method of determining the values of pure correlations between some variables in heavy ion collision. The application of this method for the analysis of the correlations of the isospin sensitive variables is pointed out.

    ↳ nucl-thhep-ph0 citations
20. 20*

    Search for light dark matter with the MESA accelerator

    Luca Doria🇩🇪 · Patrick Achenbach🇩🇪 · Mirco Christmann🇩🇪 · Achim Denig🇩🇪 · Pepe Guelker🇩🇪 · Harald Merkel🇩🇪

    At the Institute for Nuclear Physics of the Johannes Gutenberg University in Mainz, the MESA facility is currently being constructed. At its core there is a new superconducting energy-recovery linac which will provide intense electron beams for precision experiments in subatomic physics. An important part of the MESA physics program consists in the search for a "dark sector" which is a candidate explanation for the longstanding dark matter problem. This report will highlight the MESA dark sector program, and in particular two experiments will be described. The first one, MAGIX, is a two-spectrometer setup employing an internal gas-jet target installed on a recirculation arc of MESA. The second one is a beam-dump experiment for directly detecting dark matter particles. The experiments are in the R\&D phase and the current status and future prospects will be presented.

    ↳ hep-exhep-ph29 citations
21. 21*

    Isocurvature Perturbations of Dark Energy and Dark Matter from the Swampland Conjecture

    Hiroki Matsui🇯🇵 · Fuminobu Takahashi🇯🇵 · Masaki Yamada🇺🇸

    We point out that the recently proposed Swampland conjecture on the potential gradient can lead to isocurvature perturbations of dark energy, if the quintessence field acquires large quantum fluctuations during high-scale inflation preferred by the conjecture. Also, if the quintessence field is coupled to a dark sector that contains dark matter, isocurvature perturbation of dark matter is similarly induced. Both isocurvature perturbations can be suppressed if the quintessence potential allows a tracker solution in the early Universe. We find that a vector field of mass $\lesssim \mathcal{O}(1)$ meV is an excellent dark matter candidate in this context, not only because the right abundance is known to be produced by quantum fluctuations during high-scale inflation without running afoul of isocurvature bounds, but also because its coupling to the quintessence does not spoil the flatness of the potential.

    ↳ astro-ph.COhep-phhep-thPLB(2019)·26 citations
22. 22*

    Steep Eternal Inflation and the Swampland

    Konstantinos Dimopoulos🇬🇧

    I investigate whether eternal inflation is possible when the inflaton originally travels upslope the scalar potential and inevitably reaches a turn-around point where its classical kinetic energy momentarily vanishes. This behaviour occurs regardless of the steepness of the potential slope. Such steep eternal inflation, if achieved, would satisfy the recent swampland conjecture and allow eternal inflation in the string landscape.

    ↳ gr-qcastro-ph.COhep-phhep-thPRD(2018)·72 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.