Wed·Mar 4, 2020Wednesday·March 4, 2020

1. 01*

   Chemical freeze-out parameters of net-kaons in heavy-ion collisions

   Paolo Alba🇩🇪 · Rene Bellwied🇺🇸 · Valentina Mantovani-Sarti🇩🇪 · Jacquelyn Noronha-Hostler🇺🇸 · Paolo Parotto🇩🇪 · Israel Portillo-Vazquez🇺🇸 · Claudia Ratti🇺🇸 · Jamie M. Stafford🇺🇸

   We study chemical freeze-out parameters for heavy-ion collisions by performing two different thermal analyses. We analyze results from thermal fits for particle yields, as well as, net-charge fluctuations in order to characterize the chemical freeze-out. The Hadron Resonance Gas (HRG) model is employed for both methods. By separating the light hadrons from the strange hadrons in thermal fits, we study the proposed flavor hierarchy. For the net-charge fluctuations, we calculate the mean-over-variance ratio of the net-kaon fluctuations in the HRG model at the five highest energies of the RHIC Beam Energy Scan (BES) for different particle data lists. We compare these results with recent experimental data from the STAR collaboration in order to extract sets of chemical freeze-out parameters for each list. We focused on particle lists which differ largely in the number of resonant states. By doing so, our analysis determines the effect of the amount of resonances included in the HRG model on the freeze-out conditions. Our findings have potential impact on various other models in the field of relativistic heavy-ion collisions.

   hep-phnucl-thNPA(2021)·2 citations
2. 02*

   Flavorful Two Higgs Doublet Model with a Twin

   Wolfgang Altmannshofer🇺🇸 · Brian Maddock🇺🇸

   A two Higgs doublet model with flavorful Yukawa structure, in which the two doublets give mass to the third and the first two generations respectively, is combined with the twin Higgs mechanism to stabilize the Higgs mass against radiative corrections. We consider both a mirror twin and fraternal twin setup. We identify Higgs signal strength measurements and the decay $B_s\to \mu \mu$ as the most important indirect constraints on the parameter space of the model. We explore the collider phenomenology of the model and find that the heavy Higgs in the visible sector can give a sizable number of displaced decays into $b$-jets in regions of parameter space where the SM-like Higgs and the twin Higgs do not provide any striking signatures.

   hep-ph4 citations
3. 03*

   Effects of phase space variables on oscillations of modified combinants

   H. W. Ang🇸🇬 · Z. Ong🇸🇬 · P. Agarwal🇸🇬 · A. H. Chan🇸🇬 · C. H. Oh🇸🇬

   It has been shown recently that additional information can be obtained from charged particle multiplicity distribution by investigating their modified combinants $C_j$, which exhibit periodic oscillatory behaviour. The modified combinants obtained from experimental data can be expressed in a recurrent form involving the probability of obtaining $N$ charged particles $P(N)$, scaled by the void probability $P(0)$. The effects of various experimental observables such as $|\eta |$, $p_T$ and centre-of-mass collision energy $\sqrt{s}$ on the oscillatory behaviour of $C_j$ will be discussed.

   hep-phEPJ Web Conf.(2020)·0 citations
4. 04*

   Nuclear system size scan for freeze-out properties in relativistic heavy-ion collisions by using a multiphase transport model

   Dong-Fang Wang🇨🇳 · Song Zhang🇨🇳 · Yu-Gang Ma🇨🇳

   A system size scan program was recently proposed for the STAR experiments at the Relativistic Heavy Ion Collider(RHIC). In this study, we employ a multiphase transport (AMPT) model for considering the bulk properties at the freeze-out stage for ${}^{10}\mathrm{B}{+}^{10}\mathrm{B}$, ${}^{12}\mathrm{C}{+}^{12}\mathrm{C}$, ${}^{16}\mathrm{O}{+}^{16}\mathrm{O}$, ${}^{20}\mathrm{Ne}{+}^{20}\mathrm{Ne}$, ${}^{40}\mathrm{Ca}{+}^{40}\mathrm{Ca}$, ${}^{96}\mathrm{Zr}{+}^{96}\mathrm{Zr}$, and ${}^{197}\mathrm{Au}{+}^{197}\mathrm{Au}$ collisions at RHIC energies $\sqrt{s_{NN}}$ of 200, 20, and 7.7 GeV. The results for ${}^{197}\mathrm{Au}{+}^{197}\mathrm{Au}$ collisions are comparable with those of previous experimental STAR data. The transverse momentum $p_T$ spectra of charged particles (${\pi }^{\pm }$, $K^{\pm }$, $p$, and $\bar{p}$) at the kinetic freeze-out stage, based on a blast-wave model, are also discussed. In addition, we use a statistical thermal model to extract the parameters at the chemical freeze-out stage, which agree with those from other thermal model calculations. It was found that there is a competitive relationship between the kinetic freeze-out parameter $T_{kin}$ and the radial expansion velocity ${\beta }_T$, which also agrees with the STAR or ALICE results. We found that the chemical freeze-out strangeness potential ${\mu }_s$ remains constant in all collision systems and that the fireball radius $R$ is dominated by $⟨{\mathrm{N}}_{\mathrm{Part}}⟩$, which can be well fitted by a function of $a{⟨{\mathrm{N}}_{\mathrm{Part}}⟩}^b$ with $b\approx 1/3$. In addition, we calculated the nuclear modification factors for different collision systems with respect to the ${}^{10}\mathrm{B}+{}^{10}\mathrm{B}$ system, and found that they present a gradual suppression within a higher $p_T$ range from small to large systems.

   hep-phnucl-exnucl-thPRC(2020)·9 citations
5. 05*

   QCD $\theta$-vacuum energy and axion properties

   Zhen-Yan Lu🇨🇳 · Meng-Lin Du🇩🇪 · Feng-Kun Guo🇨🇳 · Ulf-G. Meißner🇩🇪 · Thomas Vonk🇩🇪

   At low energies, the strong interaction is governed by the Goldstone bosons associated with the spontaneous chiral symmetry breaking, which can be systematically described by chiral perturbation theory. In this paper, we apply this theory to study the $\theta$-vacuum energy density and hence the QCD axion potential up to next-to-leading order with $N$ non-degenerate quark masses. By setting $N=3$, we then derive the axion mass, self-coupling, topological susceptibility and the normalized fourth cumulant both analytically and numerically, taking the strong isospin breaking effects into account. In addition, the model-independent part of the axion-photon coupling, which is important for axion search experiments, is also extracted from the chiral Lagrangian supplemented with the anomalous terms up to $\mathcal{O}(p^6)$.

   hep-phhep-exhep-latJHEP(2020)·51 citations
6. 06*

   Transformation of scalar couplings between Coleman-Weinberg and MS schemes

   F.A. Chishtie🇨🇦 · Zhuo-Ran Huang🇫🇷 · M. Reimer🇨🇦 · T.G. Steele🇨🇦 · Zhi-Wei Wang🇩🇰

   The Coleman-Weinberg (CW) renormalization scheme for renormalization-group improvement of the effective potential is particularly valuable for CW symmetry-breaking mechanisms (including the challenging case of models with multiple scalar fields). CW mechanism is typically studied using models with classical scale invariance which not only provide a possibility for an alternative symmetry breaking mechanism but also partially address the gauge hierarchies through dimensional transmutation. As outlined in our discussion section, when the couplings are not large, models with CW symmetry-breaking mechanisms have also been shown to naturally provide the strong first-order phase transition necessary for stochastic gravitational wave signals. A full understanding of the CW-MS scheme transformation of couplings thus becomes important in the era of gravitational wave detection and precision coupling measurements. A generalized Coleman-Weinberg (GCW) renormalization scheme is formulated and methods for transforming scalar self-couplings between the GCW and MS (minimal-subtraction) renormalization schemes are developed. Scalar $\lambda {\Phi }^4$ theory with global $O(4)$ symmetry is explicitly studied up to six-loop order to explore the magnitude of this scheme transformation effect on the couplings. The dynamical rescaling of renormalization scales between the GCW and MS schemes can lead to significant (order of 10\%) differences in the coupling at any order, and consequently GCW-MS scheme transformation effects must be considered within precision determinations of scalar couplings in extensions of the Standard Model.

   hep-phPRD(2020)·7 citations
7. 07*

   Funnel annihilations of light dark matter and the invisible decay of the Higgs boson

   Kun Wang🇨🇳 · Jingya Zhu🇨🇳

   The semi-constrained NMSSM (scNMSSM), or NMSSM with non-universal Higgs masses, can naturally predict a light dark matter under current constraints including Higgs data, sparticle-mass bounds, dark matter searches, and muon g-2, etc. In this work, we take this scenario of scNMSSM as an example to study the funnel-annihilation mechanisms of light dark matter ($1\sim 62$ GeV) and the invisible Higgs decay. In this scenario we found that: (i) There can be four funnel-annihilation mechanisms for the LSP ${\tilde{\chi }}_1^0$, which are the $h_2$, $Z$, $h_1$ and $a_1$ funnel. (ii) For the $h_1$ and $a_1$ funnel with right relic density, the ${\tilde{\chi }}_1^0$ mass is lighter than 12 GeV, and the invisible Higgs decay can be $2\%$ at most. (iii) For the $h_2$ and $Z$ funnel with right relic density, the invisible Higgs decay can be about $0.4\%$ and $1\%$ respectively at most. (iv) If the invisible Higgs decay was discovered at the HL-LHC, the four funnel-annihilation mechanisms of light dark matter may be all excluded with ${\tilde{\chi }}_1^0$ as the only dark matter source. Four benchmark points, one for each mechanism, are proposed for future checking with updated experimental results.

   hep-phhep-exPRD(2020)·27 citations
8. 08*

   Wigner function formalism and the evolution of thermodynamic quantities in an expanding magnetized plasma

   S. M. A. Tabatabaee🇮🇷 · N. Sadooghi🇮🇷

   By combining the Wigner function formalism of relativistic quantum kinetic theory with fundamental equations of relativistic magnetohydrodynamics (MHD), we present a novel approach to determine the proper time evolution of the temperature and other thermodynamic quantities in a uniformly expanding hot, magnetized, and weakly interacting plasma. The aim is to study the contribution of quantum corrections to this evolution. We first determine the corresponding Wigner function in terms of the solution of the Dirac equation in the presence of a constant magnetic field. Using this function, we then compute the energy-momentum tensor of the above-mentioned plasma, which eventually yields its energy density and pressure. Plugging these quantities in the energy equation of relativistic MHD, we arrive, after choosing an appropriate coordinate system, at a differential equation for the temperature as a function of the proper time. The numerical solution of this equation leads finally to the proper time evolution of the temperature. The latter is then used to determine the evolution of a large number of thermodynamic quantities in this expanding and magnetized plasma. We compare our results with other existing results from relativistic MHD. We also comment on the effect of point to point decaying magnetic fields on the thermodynamic properties of this plasma.

   hep-phhep-thnucl-thPRD(2020)·18 citations
9. 09*

   Les Houches 2019: Physics at TeV Colliders: Standard Model Working Group Report

   S. Amoroso🇩🇪 · P. Azzurri🇮🇹 · J. Bendavid🇨🇭 · E. Bothmann🇩🇪 · D. Britzger🇩🇪 · H. Brooks🇦🇺 · A. Buckley🇬🇧 · M. Calvetti🇮🇹 · X. Chen🇨🇭 · M. Chiesa🇫🇷 · L. Cieri🇮🇹 · V. Ciulli🇮🇹 and 71 other authors

   This Report summarizes the proceedings of the 2019 Les Houches workshop on Physics at TeV Colliders. Session 1 dealt with (I) new developments for high precision Standard Model calculations, (II) the sensitivity of parton distribution functions to the experimental inputs, (III) new developments in jet substructure techniques and a detailed examination of gluon fragmentation at the LHC, (IV) issues in the theoretical description of the production of Standard Model Higgs bosons and how to relate experimental measurements, and (V) Monte Carlo event generator studies relating to PDF evolution and comparisons of important processes at the LHC.

   hep-phhep-ex195 citations
10. 10*

    Neutrino Portal to FIMP Dark Matter with an Early Matter Era

    Catarina Cosme🇨🇦 · Maíra Dutra🇨🇦 · Teng Ma🇮🇱 · Yongcheng Wu🇨🇦 · Litao Yang🇨🇳

    We study the freeze-in production of Feebly Interacting Massive Particle (FIMP) dark matter candidates through a neutrino portal. We consider a hidden sector comprised of a fermion and a complex scalar, with the lightest one regarded as a FIMP candidate. We implement the Type-I Seesaw mechanism for generating the masses of the Standard Model (SM) neutrinos and consider three heavy neutrinos, responsible for mediating the interactions between the hidden and the SM sectors. We assume that an early matter-dominated era (EMDE) took place for some period between inflation and Big Bang Nucleosynthesis, making the Universe to expand faster than in the standard radiation-dominated era. In this case, the hidden and SM sectors are easily decoupled and larger couplings between FIMPs and SM particles are needed from the relic density constraints. In this context, we discuss the dynamics of dark matter throughout the modified cosmic history, evaluate the relevant constraints of the model and discuss the consequences of the duration of the EMDE for the dark matter production. Finally, we show that if the heavy neutrinos are not part of the thermal bath, this scenario becomes testable through indirect detection searches.

    hep-phastro-ph.COJHEP(2021)·66 citations
11. 11*

    Dark matter and Dark photons in formal theory

    Gennady Kozlov🇷🇺

    We find the Standard Model sector (SM) interacts to Dark matter (DM) sector through the scale invariant degrees of freedom - the dilatons and Dark photons (DP). The latter have an interplay with SM via the derivatives of the scalar dilaton fields, while to DM it relates via DM current.

    hep-ph1 citation
12. 12*

    Discontinuity gravity modes in hybrid stars: assessing the role of rapid and slow phase conversions

    L. Tonetto🇧🇷 · G. Lugones🇧🇷

    Discontinuity gravity modes may arise in perturbed quark-hadron hybrid stars when a sharp density jump exists in the stellar interior and are a potential fingerprint to infer the existence of quark matter cores in compact objects. When a hybrid star is perturbed, conversion reactions may occur at the quark-hadron interface and may have a key role in global stellar properties such as the dynamic stability and the quasi-normal mode spectrum. In this work we study the role of the conversion rate at the interface. To this end, we first derive the junction conditions that hold at the sharp interface of a non-radially perturbed hybrid star in the case of slow and rapid conversions. Then, we analyse the discontinuity $g$-mode in both cases. For rapid conversions, the discontinuity $g$-mode has zero frequency because a displaced fluid element near the phase splitting surface adjusts almost immediately its composition to its surroundings and gravity cannot provide a buoyancy force. For slow conversions, a $g$-mode exists and its properties are analysed here using modern hadronic and quark equations of state. Moreover, it has been shown recently that in the case of slow conversions an extended branch of stable hybrid configurations arises for which $\partial M/\partial {ϵ}_c<0$. We show that $g$-modes of the standard branch (that is, the one with $\partial M/\partial {ϵ}_c>0$) have frequencies and damping times in agreement with previous results in the literature. However, $g$-modes of the extended branch have significantly larger frequencies (in the range $1-2\mathrm{kHz}$) and much shorter damping times (few seconds in some cases). We discuss the detectability of $g$-mode GWs with present and planned GW observatories.

    ↳ astro-ph.HEgr-qchep-phPRD(2020)·52 citations
13. 13*

    Emergence of Einstein Gravity from Weyl Gravity

    Ichiro Oda🇯🇵

    It is shown that in a quadratic gravity based on Weyl's conformal geometry, not only the Einstein-Hilbert action emerges but also a Weyl gauge field becomes massive in the Weyl gauge condition, $\tilde{R}=k$, for a Weyl gauge symmetry within the framework of the BRST formalism. We also consider a more general gravitational theory with a scalar field in the Weyl geometry and see that the Einstein-Hilbert action can be induced from spontaneous symmetry breakdown of the Weyl gauge symmetry. Thus, it turns out that Weyl's conformal gravity is quantum mechanically equivalent to Einstein's general relativity plus a massive Weyl gauge field, and the Weyl geometry is free from an infamous ``second clock problem'' in quantum regime.

    ↳ hep-thgr-qchep-ph12 citations
14. 14*

    Predicting the orbifold origin of the MSSM

    Erik Parr🇩🇪 · Patrick K.S. Vaudrevange🇩🇪 · Martin Wimmer🇩🇪

    MSSM-like string models from the compactification of the heterotic string on toroidal orbifolds (of the kind $T^6/P$) have distinct phenomenological properties, like the spectrum of vector-like exotics, the scale of supersymmetry breaking, and the existence of non-Abelian flavor symmetries. We show that these characteristics depend crucially on the choice of the underlying orbifold point group $P$. In detail, we use boosted decision trees to predict $P$ from phenomenological properties of MSSM-like orbifold models. As this works astonishingly well, we can utilize machine learning to predict the orbifold origin of the MSSM.

    ↳ hep-thhep-phFortsch.Phys.(2020)·15 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.