Tue·Mar 6, 2018Tuesday·March 6, 2018

1. 01*

   Primordial gravitational waves, precisely: The role of thermodynamics in the Standard Model

   Ken'ichi Saikawa🇩🇪 · Satoshi Shirai🇯🇵

   In this paper, we revisit the estimation of the spectrum of primordial gravitational waves originated from inflation, particularly focusing on the effect of thermodynamics in the Standard Model of particle physics. By collecting recent results of perturbative and non-perturbative analysis of thermodynamic quantities in the Standard Model, we obtain the effective degrees of freedom including the corrections due to non-trivial interaction properties of particles in the Standard Model for a wide temperature interval. The impact of such corrections on the spectrum of primordial gravitational waves as well as the damping effect due to free-streaming particles is investigated by numerically solving the evolution equation of tensor perturbations in the expanding universe. It is shown that the reevaluation of the effects of free-streaming photons and neutrinos gives rise to some additional damping features overlooked in previous studies. We also observe that the continuous nature of the QCD crossover results in a smooth spectrum for modes that reenter the horizon at around the epoch of the QCD phase transition. Furthermore, we explicitly show that the values of the effective degrees of freedom remain smaller than the commonly used value 106.75 even at temperature much higher than the critical temperature of the electroweak crossover, and that the amplitude of primordial gravitational waves at a frequency range relevant to direct detection experiments becomes $\mathcal{O}(1)\%$ larger than previous estimates that do not include such corrections. This effect can be relevant to future high-sensitivity gravitational wave experiments such as ultimate DECIGO. Our results on the temperature evolution of the effective degrees of freedom are made available as tabulated data and fitting functions, which can also be used in the analysis of other cosmological relics.

   hep-phastro-ph.COgr-qcJCAP(2018)·344 citations
2. 02*

   Fragmentation of charm to charmonium in $e^{+}{e}^{-}$ and $pp$ collisions

   S.P. Baranov🇷🇺 · B.Z. Kopeliovich🇨🇱

   We perform numerical comparison of the fragmentation mechanism of charmonium production ($gg\to c\bar{c}$ followed by $c\to \psi c$) with the full leading order calculation ($gg\to \psi c\bar{c}$ at $\text{O}({\alpha }_s^4)$). We conclude that the non-fragmentation contributions remain important up to $J/\psi$ transverse momenta about as large as 50 GeV, thus making questionable the applicability of the fragmentation approximation at smaller transverse momenta.

   hep-phEPJC(2019)·4 citations
3. 03*

   Double-parton scattering effects in $D^0{B}^{+}$ and $B^{+}{B}^{+}$ meson-meson pair production in proton-proton collisions at the LHC

   Rafal Maciula🇵🇱 · Antoni Szczurek🇵🇱

   We extend our previous studies of double-parton scattering (DPS) to simultaneous production of $c\bar{c}$ and $b\bar{b}$ and production of two pairs of $b\bar{b}$. The calculation is performed within factorized ansatz. Each parton scattering is calculated within $k_T$-factorization approach. The hadronization is done with the help of fragmentation functions. Production of $D$ mesons in our framework was tested in our previous works. Here we present our predictions for $B$ mesons. A good agreement is achieved with the LHCb data. We present our results for $c\bar{c}b\bar{b}$ and $b\bar{b}b\bar{b}$ final states. For completeness we compare results for double- and single-parton scattering (SPS). As for $c\bar{c}c\bar{c}$ final state also here the DPS dominates over the SPS, especially for small transverse momenta. We present several distributions and integrated cross sections with realistic cuts for simultaneous production of $D^0{B}^{+}$ and $B^{+}{B}^{+}$, suggesting future experimental studies at the LHC.

   hep-phhep-exPRD(2018)·8 citations
4. 04*

   Coherent Elastic Neutrino Nucleus Scattering (CE$\nu$NS) as a probe of $Z^{\prime }$ through kinetic and mass mixing effects

   Mohammad Abdullah🇺🇸 · James B. Dent🇺🇸 · Bhaskar Dutta🇺🇸 · Gordon L. Kane🇺🇸 · Shu Liao🇺🇸 · Louis E. Strigari🇺🇸

   We examine the current constraints and future sensitivity of Coherent Elastic Neutrino-Nucleus Scattering (CE$\nu$NS) experiments to mixing scenarios involving a $Z^{\prime }$ which interacts via portals with the Standard Model. We contrast the results against those from fixed target, atomic parity violation, and solar neutrino experiments. We demonstrate a significant dependence of the experimental reach on the $Z^{\prime }$ coupling non-universality and the complementarity of CE$\nu$NS to existing searches.

   hep-phhep-exPRD(2018)·133 citations
5. 05*

   The Radion as a Dark Matter Candidate

   Fayez Abu-Ajamieh🇺🇸

   I study a class of Randall-Sundrum (RS) models with Spontaneous Breaking of Scale Invariance (SBSI). This class of models implements the Contino-Pomarol-Rattazzi (CPR) mechanism to achieve SBSI through the small running of an external close-to-marginal scale-breaking operator that leads to a light dilaton/radion with couplings to matter suppressed by the small running. I show that for radion masses $\lesssim 1$ KeV, it can serve as a Dark Matter (DM) candidate, with a lifetime longer than the age of the universe, and show that the experimental bounds from LHC, Non-Newtonian Gravity and Axion-Like Particle (ALP) searches allow for the existence of such a radion.

   hep-phInt.J.Mod.Phys.A(2018)·4 citations
6. 06*

   $SU(2{)}_L$ Doublet Vector Dark Matter from Gauge-Higgs Unification

   Nobuhito Maru🇯🇵 · Nobuchika Okada🇺🇸 · Satomi Okada🇯🇵

   A new vector dark matter (DM) scenario in the context of the gauge-Higgs unification (GHU) is proposed. The DM particle is identified with an electric-charge neutral component in an $SU(2{)}_L$ doublet vector field with the same quantum number as the Standard Model Higgs doublet. Since such an $SU(2{)}_L$ doublet vector field is incorporated in any models of the GHU scenario, it is always a primary and model-independent candidate for the DM in the scenario. The observed relic density is reproduced through a DM pair annihilations into the weak gauge bosons with a TeV-scale DM mass, which is nothing but the compactification scale of extra-dimensions. Due to the higher-dimensional gauge structure of the GHU scenario, a pair of the DM particles has no direct coupling with a single $Z$-boson/Higgs boson, so that the DM particle evades the severe constraint from the current direct DM search experiments.

   hep-phhep-thPRD(2018)·18 citations
7. 07*

   The semi-leptonic and non-leptonic weak decays of ${\Lambda }_b^0$

   Jie Zhu🇨🇳 · Zheng-Tao Wei🇨🇳 · Hong-Wei Ke🇺🇸

   The recent experimental developments require a more precise theoretical study of weak decays of heavy baryon ${\Lambda }_b^0$. In this work, we provide an updated and systematic analysis of both the semi-leptonic and nonleptonic decays of ${\Lambda }_b^0$ into baryons ${\Lambda }_c^{+}$, $\Lambda$, $p$, and $n$. The diquark approximation is adopted so that the methods developed in the $B$ meson system can be extended into the baryon system. The baryon-to-baryon transition form factors are calculated in the framework of a covariant light-front quark model. The form factors $f_3,g_3$ can be extracted and are found to be non-negligible. The semi-leptonic processes of ${\Lambda }_b^0\to {\Lambda }_c^{+}(p)l^{-}{\bar{\nu }}_l$ are calculated and the results are consistent with the experiment. We study the non-leptonic processes within the QCD factorization approach. The decay amplitudes are calculated at the next-to-leading order in strong coupling constant ${\alpha }_s$. We calculate the non-leptonic decays of ${\Lambda }_b^0$ into a baryon and a s-wave meson (pseudoscalar or vector) including 44 processes in total. The branching ratios and direct CP asymmetries are predicted. The numerical results are compared to the experimental data and those in the other theoretical approaches. Our results show validity of the diquark approximation and application of QCD factorization approach into the heavy baryon system.

   hep-phhep-exPRD(2019)·62 citations
8. 08*

   Effective-energy universality approach describing total multiplicity centrality dependence in heavy-ion collisions

   Edward K. Sarkisyan-Grinbaum🇨🇭 · Aditya Nath Mishra🇲🇽 · Raghunath Sahoo🇮🇳 · Alexander S. Sakharov🇺🇸

   The recently proposed participant dissipating effective-energy approach is applied to describe the dependence on centrality of the multiplicity of charged particles measured in heavy-ion collisions at the collision energies up to the highest LHC energy of 5 TeV. The effective-energy approach relates multihadron production in different types of collisions, by combining, under the proper collision energy scaling, the constituent quark picture with Landau relativistic hydrodynamics. The measurements are shown to be well described in terms of the centrality-dependent effective energy of participants and an explanation of the differences in the measurements at RHIC and LHC are given by means of the recently introduced hypothesis of the energy-balanced limiting fragmentation scaling. A similarity between the centrality data and the data from most central collisions is proposed pointing to the central character of participant interactions independent of centrality. The findings complement our recent investigations of the similar midrapidity pseudorapidity density measurements extending the description to the full pseudorapidity range in view of the considered similarity of multihadron production in nucleon interactions and heavy-ion collisions.

   hep-phhep-exnucl-exnucl-thEPL(2019)·21 citations
9. 09*

   Loop effects on the Higgs decay widths in extended Higgs models

   Shinya Kanemura🇯🇵 · Mariko Kikuchi🇹🇼 · Kentarou Mawatari🇯🇵 · Kodai Sakurai🇯🇵 · Kei Yagyu🇮🇹

   In order to identify the Higgs sector using future precision data, we calculate the partial decay widths of the discovered Higgs boson with the mass of 125 GeV into fermion pairs and gauge-boson pairs with one-loop electroweak and one-loop QCD corrections in various extended Higgs models, such as the Higgs singlet model and four types of two Higgs doublet models. In the tree-level analysis, the patterns of deviations from the standard model predictions in the partial decay widths for various decay modes are distinctive for each model, due to the mixing of the Higgs boson with other neutral scalars. Our present analysis shows that even with a full set of radiative corrections we can discriminate these extended Higgs models via the partial decay widths as long as any of the deviations is detected at future precision measurements. Furthermore, we quantitatively show that in each model the magnitude of the deviations can provide important information on the mass scale of extra Higgs bosons under the theoretical constraints from perturbative unitary and vacuum stability, which can be obtained without discovery of the additional Higgs bosons.

   hep-phPLB(2018)·33 citations
10. 10*

    Weak Decays of Triply Heavy Baryons

    Wei Wang🇨🇳 · Ji Xu🇨🇳

    After the experimental establishment of doubly heavy baryons, baryons with three quarks are the last missing pieces of the lowest-lying baryon multiplets in quark model. In this work we study semileptonic and nonleptonic weak decays of triply heavy baryons, ${\Omega }_{ccc}^{++},{\Omega }_{ccb}^{+},{\Omega }_{cbb}^0,{\Omega }_{bbb}^{-}$. Decay amplitudes for various channels are parametrized in terms of a few SU(3) irreducible amplitudes. We point out that branching fractions for Cabibbo allowed processes, ${\Omega }_{ccc}\to ({\Xi }_{cc}^{++}{\overline{K}}^0,{\Xi }_{cc}^{++}{K}^{-}{\pi }^{+},{\Omega }_{cc}^{+}{\pi }^{+},{\Xi }_c^{+}{D}^{+},{\Xi }_c^{\prime }{D}^{+},{\Lambda }_c{D}^{+}{\overline{K}}^0,{\Xi }_c^{+}{D}^0{\pi }^{+},{\Xi }_c^0{D}^{+}{\pi }^{+})$ may reach a few percents. We suggest our experimental colleagues to perform a search at hadron colliders and the electron and positron collisions in future, which will presumably lead to discoveries of triply heavy baryons and complete the baryon multiplets. Using the expanded amplitudes, we derive a number of relations for the partial widths which can be examined in future.

    hep-phPRD(2018)·50 citations
11. 11*

    Production of open-charm mesons in relativistic heavy-ion collisions

    Shuang Li🇨🇳 · Chaowen Wang🇨🇳 · Xianbao Yuan🇨🇳 · Shengqin Feng🇨🇳

    We present a theoretical framework to study open charm production in relativistic heavy-ion collisions. The coupling strength between the charm quarks and the QGP constituents, quantified by the spatial diffusion coefficient $2\pi T{D}_s$, is obtained by performing a phenomenological fit analysis to the lattice QCD calculations, resulting in $2\pi T{D}_s=const.$ (\textbf{Model-A}) and $2\pi T{D}_s=1.3+(T/T_c{)}^2$ (\textbf{Model-B}). We find that the relative azimuthal distribution of the initially back-to-back generated $c\bar{c}$ pairs presents a broadening behaviour, which is more pronounced for $c\bar{c}$ pairs with small initial $p_{\mathrm{T}}$, and when the Model-B approach is adopted. The competition between the initial drag and the subsequent collective effects tends to restrict the time dependence of charm quark $R_{\mathrm{AA}}$. Concerning the theoretical uncertainty on final D-meson nuclear modification, the nuclear shadowing and pp baseline components are dominat at high and low $p_{\mathrm{T}}$ ($p_{\mathrm{T}}\lesssim 3GeV/c$), respectively. The measured D-meson $R_{\mathrm{AA}}(p_{\mathrm{T}})$ favors Model-A assumption for the diffusion coefficient both at RHIC and LHC, while their $v_2(p_{\mathrm{T}})$ prefer Model-B at moderate $p_{\mathrm{T}}$. These results confirm the necessity to consider the temperature- and/or momentum-dependence of $2\pi T{D}_s$ to describe well the D-meson $R_{\mathrm{AA}}$ and $v_2$ simultaneously.

    hep-phnucl-thPRC(2018)·22 citations
12. 12*

    Deep-Learning in Search of Light Charged Higgs

    Guleser. K. Demir🇹🇷 · Nasuf Sonmez🇹🇷 · Hatice Dogan🇹🇷

    In this work, we deep-learn light charged Higgs signal in top quark decays which poses difficulties due to strong W boson contamination. We construct Deep Neural Networks (DNN) with appropriate architecture and determine signal extraction efficiency by considering various features (kinematical and human engineered parameters). Results show that DNN gives better performance than the classical neural networks and has ability to find regions of high efficiency even the input features are not human-engineered. In a sense, human-engineered high-level features are offset by DNNs with different combinations of the low-level kinematical features. Additionally, it is shown that increasing the number of processing units in DNNs does not necessarily cause an increase in efficiency due mainly to increased complexity. Our method and results can set an example of signal extraction from strong backgrounds.

    hep-ph7 citations
13. 13*

    Loop Effects in Direct Detection

    Nicole F. Bell🇦🇺 · Giorgio Busoni🇦🇺 · Isaac W. Sanderson🇦🇺

    We consider loop level contributions to dark matter scattering off nucleons in cases where the spin independent scattering cross section is absent or suppressed at tree level. In the case of a pseudoscalar interaction, for which the tree level cross section is both spin-dependent and suppressed by 4 powers of the exchanged momentum, we show that loop diagrams give rise to a non- zero spin independent cross section. Importantly, if the pseudoscalar interaction is formulated using a gauge invariant framework, loop effects generate an effective $\bar{\chi }\chi h$ vertex and result in a scattering cross section that is within reach of current or forthcoming experiments. We also consider the case of inelastic dark matter, for which the tree-level direct detection cross section is negligible when the inelastic ${\chi }_{1}N\to {\chi }_{2}N$ process is kinematically suppressed. In this case, loop diagrams generate an interaction with both initial and final ${\chi }_1$ states and hence permit measurable, spin independent, ${\chi }_{1}N\to {\chi }_{1}N$ elastic scattering. As such, we are able to probe parameter space that was previously considered inaccessible to direct detection

    hep-phJCAP(2018)·66 citations
14. 14*

    Elliptic flow of hadrons via quark coalescence mechanism using Boltzmann transport equation for Pb+Pb collision at $\sqrt{s_{NN}}$=2.76 TeV

    Mohammed Younus🇮🇳 · Sushanta Tripathy🇮🇳 · Swatantra Kumar Tiwari🇮🇳 · Raghunath Sahoo🇮🇳

    Elliptic flow of hadrons observed at relativistic heavy-ion collision experiments at Relativistic Heavy-Ion Collider (RHIC) and Large Hadron Collider (LHC), provides us an important signature of possible de-confinement transition from hadronic phase to partonic phase. However, hadronization processes of de-confined partons back into final hadrons are found to play a vital role in the observed hadronic flow. In the present work, we use coalescence mechanism also known as Recombination (ReCo) to combine quarks into hadrons. To get there, we have used Boltzmann transport equation in relaxation time approximation to transport the quarks into equilibration and finally to freeze-out surface, before coalescence takes place. A Boltzmann-Gibbs Blast Wave (BGBW) function is taken as an equilibrium function to get the final distribution and a power-like function to describe the initial distributions of partons produced in heavy-ion collisions. In the present work, we try to estimate the elliptic flow of identified hadrons such as $\pi$, $K$, $p$ etc., produced in Pb+Pb collisions at $\sqrt{s_{\mathrm{NN}}}$ = 2.76 TeV at the LHC for different centralities. The elliptic flow ($v_2$) of identified hadrons seems to be described quite well in the available $p_{\mathrm{T}}$ range. After the evolution of quarks until freeze-out time, has been calculated using BTE-RTA, the approach used in this paper consists of combining two or more quarks to explain the produced hadrons at intermediate momenta regions. The formalism is found to describe elliptic flow of hadrons produced in Pb+Pb collisions to a large extent.

    hep-phhep-exnucl-exnucl-thAdv.High Energy Phys.(2020)·7 citations
15. 15*

    Optimal Impedance Matching and Quantum Limits of Electromagnetic Axion and Hidden-Photon Dark Matter Searches

    Saptarshi Chaudhuri🇺🇸 · Kent Irwin🇺🇸 · Peter W. Graham🇺🇸 · Jeremy Mardon🇺🇸

    For the first time, we determine the properties of the optimal single-moded, linear, passive search for electromagnetic coupling to axion and hidden-photon dark matter, subject to the Standard Quantum Limit on phase-insensitive amplification. We establish the parameters that must be considered to determine the optimal search: the impedance match to dark matter; receiver frequency-response and tuning; irreducible noise sources; and prior information on the dark-matter signal. Using complex-power flow equations, we identify two categories of coupling to the dark-matter signal: radiative and reactive. We motivate a focus on single-moded reactive couplings, as receivers using solely radiative couplings are limited in sensitivity by mismatch with the dark-matter source impedance. We define integrated sensitivity as a figure of merit in comparing searches over a wide frequency range and show that the Bode-Fano criterion sets a limit on integrated sensitivity in a reactively coupled receiver. We examine single-pole resonators, a broadly used form of reactive coupling, and show that when thermal noise dominates amplifier noise and noise matching is optimized, substantial sensitivity is available away from the resonator bandwidth. The Bode-Fano constraint establishes the single-pole resonator as near-ideal for single-moded dark-matter detection. Additionally, the optimized resonator is superior to the optimized reactive broadband receiver at all frequencies at which a resonator may practically be made. We optimize time allocation in a tunable resonator search using priors and derive quantum limits on resonant search sensitivity. At low frequencies, the application of our optimization may enhance scan rates by a few orders of magnitude. While our results broadly inform laboratory searches for light fields, they are the basis for DMRadio, a DOE-funded program in axion and hidden-photon detection.

    hep-ph89 citations
16. 16*

    The first $\Delta (27)$ flavor 3-3-1 model with low scale seesaw mechanism

    A. E. Cárcamo Hernández🇨🇱 · H. N. Long🇻🇳 · V. V. Vien🇻🇳

    We propose a viable model based on the $SU(3{)}_C\times SU(3{)}_L\times U(1{)}_X$ gauge group, augmented by the $U(1{)}_{L_g}$ global lepton number symmetry and the $\Delta (27)\times Z_3\times Z_{16}$ discrete group, capable of explaining the Standard Model (SM) fermion masses and mixings, and having a low scale seesaw mechanism which can be tested at the LHC. In addition the model provides an explanation for the SM fermion masses and mixings. In the proposed model, small masses for the light active neutrinos are generated by an inverse seesaw mechanism caused by non renormalizable Yukawa operators and mediated by three very light Majorana neutrinos and the observed hierarchy of the SM fermion masses and mixing angles is produced by the spontaneous breaking of the $\Delta (27)\times Z_3\times Z_{16}$ symmetry at very large energy scale. This neutrino mass generation mechanism is not presented in our previous 3-3-1 models with $\Delta (27)$ group (Nucl.Phys. B913 (2016) 792-814 and Eur.Phys.J. C76 (2016) no.5, 242), where the masses of the light active neutrinos arise from a combination of type I and type II seesaw mechanisms (Nucl.Phys. B913 (2016) 792-814) as well as from a double seesaw mechanism (Eur.Phys.J. C76 (2016) no.5, 242). Thus, this work corresponds to the first implementation of the $\Delta (27)$ symmetry in a 3-3-1 model with low scale seesaw mechanism.

    hep-phEPJC(2018)·51 citations
17. 17*

    Strange baryons with two heavy quarks

    Marek Karliner🇮🇱 · Jonathan L. Rosner🇺🇸

    The LHCb Experiment at CERN has observed a doubly-charmed baryon ${\Xi }_{cc}^{++}=ccu$ with a mass of $3621.40\pm 0.78$ MeV, consistent with many predictions. We use the same methods that led us to predict $M({\Xi }_{cc},J^P=1/2^{+})=3627\pm 12$ MeV and $M({\Xi }_{cc}^{\ast },J^P=3/2^{+})=3690\pm 12$ MeV to predict $M({\Omega }_{cc}^{+},J^P=1/2^{+})=3692\pm 16$ MeV and $M({\Omega }_{cc}^{\ast },J^P=3/2^{+})=3756\pm 16$ MeV. Production and decay are discussed briefly, and predictions for $M({\Omega }_{bc})$ and $M({\Omega }_{bb})$ are included.

    hep-phhep-exPRD(2018)·34 citations
18. 18*

    Sub-TeV Quintuplet Minimal Dark Matter with Left-Right Symmetry

    Sanjib Kumar Agarwalla🇮🇳 · Kirtiman Ghosh🇮🇳 · Ayon Patra🇮🇳

    A detailed study of a fermionic quintuplet dark matter in a left-right symmetric scenario is performed in this article. The minimal quintuplet dark matter model is highly constrained from the WMAP dark matter relic density (RD) data. To elevate this constraint, an extra singlet scalar is introduced. It introduces a host of new annihilation and co-annihilation channels for the dark matter, allowing even sub-TeV masses. The phenomenology of this singlet scalar is studied in detail in the context of the Large Hadron Collider (LHC) experiment. The production and decay of this singlet scalar at the LHC give rise to interesting resonant di-Higgs or diphoton final states. We also constrain the RD allowed parameter space of this model in light of the ATLAS bounds on the resonant di-Higgs and diphoton cross-sections.

    hep-phJHEP(2018)·11 citations
19. 19*

    Light scalar dark matter at neutrino oscillation experiments

    Jiajun Liao🇺🇸 · Danny Marfatia🇺🇸 · Kerry Whisnant🇺🇸

    Couplings between light scalar dark matter (DM) and neutrinos induce a perturbation to the neutrino mass matrix. If the DM oscillation period is smaller than ten minutes (or equivalently, the DM particle is heavier than $0.69\times 10^{-17}$ eV), the fast-averaging over an oscillation cycle leads to a modification of the measured oscillation parameters. We present a specific $\mu -\tau$ symmetric model in which the measured value of ${\theta }_{13}$ is entirely generated by the DM interaction, and which reproduces the other measured oscillation parameters. For a scalar DM particle lighter than $10^{-15}$ eV, adiabatic solar neutrino propagation is maintained. A suppression of the sensitivity to CP violation at long-baseline neutrino experiments is predicted in this model. We find that DUNE cannot exclude the DM scenario at more than $3\sigma$ C.L. for bimaximal, tribimaximal and hexagonal mixing, while JUNO can rule it out at more than $6\sigma$ C.L. by precisely measuring both ${\theta }_{12}$ and ${\theta }_{13}$.

    hep-phastro-ph.COhep-exJHEP(2018)·50 citations
20. 20*

    Improved predictions for magnetic moments and M1 decay widths of heavy hadrons

    Vytautas Simonis🇱🇹

    In the framework of an extended bag model the magnetic moments, M1 transition moments, and decay widths of all ground-state heavy hadrons are calculated. For the heavy baryons containing three quarks of different flavors the effect of hyperfine mixing of the states is taken into account. The additional care is taken to get more accurate theoretical estimates for the mass splittings of heavy hadrons. The use of such improved values enables one to provide more accurate predictions for the decay widths. These values of the hyperfine splittings between baryons may be also useful for the further experimental searches of new heavy hadrons. For instance, we predict $M({\Xi }_{cc}^{\ast })=3695\pm 5$ MeV. The agreement of our results for the M1 decay rates with available experimental data is good. We also present a wide comparison of the predictions obtained in our work with the results obtained using various other approaches.

    hep-ph61 citations
21. 21*

    Update of the global electroweak fit and constraints on two-Higgs-doublet models

    Johannes Haller🇩🇪 · Andreas Hoecker🇨🇭 · Roman Kogler🇩🇪 · Klaus Mönig🇩🇪 · Thomas Peiffer🇩🇪 · Jörg Stelzer🇨🇭

    We present an update of the global fit of the Standard Model electroweak sector to latest experimental results. We include new kinematic top quark and $W$ boson mass measurements from the LHC, a ${\sin }^2{\theta }_{\mathrm{eff}}^{\ell }$ result from the Tevatron, and a new evaluation of the hadronic contribution to $\alpha (M_Z^2)$. We present tests of the internal consistency of the electroweak Standard Model and updated numerical predictions of key observables. The electroweak data combined with measurements of the Higgs boson coupling strengths and flavour physics observables are used to constrain parameters of two-Higgs-doublet models.

    hep-phhep-exEPJC(2018)·565 citations
22. 22*

    Supersymmetry versus Compositeness: 2HDMs tell the story

    Stefania De Curtis🇮🇹 · Luigi Delle Rose🇮🇹 · Stefano Moretti🇬🇧 · Kei Yagyu🇮🇹

    Supersymmetry and Compositeness are two prevalent paradigms providing both a solution to the hierarchy problem and a motivation for a light Higgs boson state. As the latter has now been found, its dynamics can hold the key to disentangle the two theories. An open door towards the solution is found in the context of 2-Higgs Doublet Models (2HDMs), which are necessary to Supersymmetry and natural within Compositeness in order to enable Electro-Weak Symmetry Breaking. We show how 2HDM spectra of masses and couplings accessible at the Large Hadron Collider may allow one to separate the two scenarios.

    hep-phhep-thPLB(2018)·22 citations
23. 23*

    Spin-2 Portal Dark Matter

    Nicolas Bernal🇨🇴 · Maira Dutra🇫🇷 · Yann Mambrini🇫🇷 · Keith A. Olive🇺🇸 · Marco Peloso🇺🇸 · Mathias Pierre🇫🇷

    We generalize models invoking a spin-2 particle as a mediator between the dark sector and the Standard Model. We show that a massive spin-2 messenger can efficiently play the role of a portal between the two sectors. The dark matter is then produced via a freeze-in mechanism during the reheating epoch. In a large part of the parameter space, production through the exchange of a massive spin-2 mediator dominates over processes involving a graviton with Planck suppressed couplings. We perform a systematic analysis of such models for different values of the spin-2 mass relative to the maximum and the final temperature attained at reheating.

    hep-phastro-ph.HEhep-thPRD(2018)·165 citations
24. 24*

    Hydrodynamic fluctuations from a weakly coupled scalar field

    G. Jackson🇨🇭 · M. Laine🇨🇭

    Studies of non-equilibrium dynamics of cosmological phase transitions may involve a scalar field interacting weakly with the energy-momentum tensor of a thermal plasma. At late times, when the scalar field is approaching equilibrium, it experiences both damping and thermal fluctuations. We show that thermal fluctuations induce a shear viscosity and a gravitational wave production rate, and propose that including this tunable contribution may help in calibrating the measurement of the gravitational wave production rate in hydrodynamic simulations. Furthermore it may enrich their physical scope, permitting in particular for a study of the instability of growing bubbles.

    hep-phastro-ph.COEPJC(2018)·13 citations
25. 25*

    Axion Searches with Microwave Filters: the RADES project

    Alejandro Álvarez Melcón🇪🇸 · Sergio Arguedas Cuendis🇨🇭 · Cristian Cogollos🇪🇸 · Alejandro Díaz-Morcillo🇪🇸 · Babette Döbrich🇨🇭 · Juan Daniel Gallego🇪🇸 · Benito Gimeno🇪🇸 · Igor G. Irastorza🇪🇸 · Antonio José Lozano-Guerrero🇪🇸 · Chloé Malbrunot🇨🇭 · Pablo Navarro🇪🇸 · Carlos Peña Garay🇪🇸 and 3 other authors

    We propose, design and construct a variant of the conventional axion haloscope concept that could be competitive in the search for dark matter axions of masses in the decade 10-100 $\mu$eV. Theses masses are located somewhat above the mass range in which existing experiments have reached sensitivity to benchmark QCD axion models. Our haloscope consists of an array of small microwave cavities connected by rectangular irises, in an arrangement commonly used in radio-frequency filters. The size of the unit cavity determines the main resonant frequency, while the possibility to connect a {large} number of cavities allows to reach large detection volumes. We develop the theoretical framework of the detection concept, and present design prescriptions to optimize detection capabilities. We describe the design and realization of a first small-scale prototype of this concept, called Relic Axion Detector Exploratory Setup (RADES). It consists of a copper-coated stainless steel five-cavities microwave filter with the detecting mode operating at around 8.4 GHz. This structure has been electromagnetically characterized at 2 K and 298 K, and it is now placed in ultra-high vacuum in one of the twin-bores of the 9 T CAST dipole magnet at CERN. We describe the data acquisition system developed for relic axion detection, and present preliminary results of the electromagnetic properties of the microwave filter, which show the potential of filters to reach QCD axion window sensitivity at X-band frequencies.

    ↳ hep-exhep-phJCAP(2018)·124 citations
26. 26*

    Quantification of GR effects in muon g-2, EDM and other spin precession experiments

    Andras Laszlo🇭🇺 · Zoltan Zimboras🇭🇺

    Recently, Morishima, Futamase and Shimizu published a series of manuscripts, putting forward arguments, based on a post-Newtonian approximative calculation, that there can be a sizable general relativistic (GR) correction in the experimental determination of the muon magnetic moment based on spin precession, i.e., in muon g-2 experiments. In response, other authors argued that the effect must be much smaller than claimed. Further authors argued that the effect exactly cancels. Also, the known formulae for de Sitter and Lense-Thirring effect do not apply due to the non-geodesic motion. All this indicates that it is difficult to estimate from first principles the influence of GR corrections in the problem of spin propagation. Therefore, in this paper we present a full general relativistic calculation in order to quantify this effect. The main methodology is the purely differential geometrical tool of Fermi-Walker transport over a Schwarzschild background. Also the Larmor precession due to the propagation in the electromagnetic field of the experimental apparatus is included. For the muon g-2 experiments the GR correction turns out to be very small, well below the present sensitivity. However, in other similar storage ring experimental settings, such as electric dipole moment (EDM) search experiments, where the so-called frozen spin method is used, GR gives a well detectable effect, and should be corrected for. All frozen spin scenarios are affected which intend to reach a sensitivity of 0.1 microradians/second for the spin precession in the vertical plane.

    ↳ gr-qchep-phhep-thClass.Quant.Grav.(2018)·24 citations
27. 27*

    Vortex rings in fragmentation regions in heavy-ion collisions at $\sqrt{s_{NN}}=$ 39 GeV

    Yu. B. Ivanov🇷🇺 · A. A. Soldatov🇷🇺

    Vorticity generated in heavy-ion collisions at energy of $\sqrt{s_{NN}}=$ 39 GeV is studied. Simulations are performed within a model of the three-fluid dynamics. A peculiar structure consisting of two vortex rings is found: one ring in the target fragmentation region and another one in the projectile fragmentation region. These rings are also formed in central collisions. The matter rotation is opposite in this two rings. These vortex rings are already formed at the early stage of the collision together with primordial fragmentation regions. The average vorticity, responsible for the global polarization of the observed $\Lambda$ and $\bar{\Lambda }$, is also studied. In the semi-central collisions the average vorticity in the midrapidity region turns out to be more than an order of magnitude lower than the total one. The total vorticity is dominated by the contributions of the fragmentation regions and is produced because of asymmetry of the vortex rings in noncentral collisions. This suggests that in semi-central collisions the global polarization in the fragmentation regions should be at least an order of magnitude higher than that observed by the STAR collaboration in the midrapidity. This polarization should be asymmetrical in the reaction plain and correlate with the corresponding directed flow.

    ↳ nucl-thhep-phPRC(2018)·30 citations
28. 28*

    Energy dependence of light (anti)nuclei and (anti)hypertriton production in the Au-Au collision from $\sqrt{s_{\mathrm{NN}}}=5.0$ to $5020$ GeV

    Zi-Jian Dong🇨🇳 · Gang Chen🇨🇳 · Quan-Yu Wang🇨🇳 · Zhi-Lei She🇨🇳 · Yu-Liang Yan🇨🇳 · Feng-Xian Liu🇨🇳 · Dai-Mei Zhou🇨🇳 · Ben-Hao Sa🇨🇳

    The energy dependence of light (anti)nuclei and (anti)hypertriton production are investigated in central Au-Au collisions from AGS up to LHC energies at midrapidity, using the parton and hadron cascade model (PACIAE) together with the dynamically constrained phase-space coalescence model(DCPC). We find that the yields, yield ratios of the antiparticles to their corresponding particles, the coalescence parameters $B_A$ and the strangeness population factor $s_3$ of light (anti)nuclei and (anti)hypertriton strongly depend on the energy. Furthermore, we analyze and discuss the strangeness population factor $s_3$ and the coalescence parameters $B_A$, and find a transition point near by 20 GeV. These results thus suggest the potential usefulness of the $s_3$ and $B_A$ of light nuclei production in relativistic heavy-ion collisions as a direct probe of the transition point associated with the QCD critical phenomena. The results from PACIAE+DCPC model are well consistent with experimental data.

    ↳ nucl-thhep-phEPJA(2018)·30 citations
29. 29*

    Robust extraction of proton charge radius from electron-proton scattering data

    Xuefei Yan🇺🇸 · Douglas W. Higinbotham🇺🇸 · Dipangkar Dutta🇺🇸 · Haiyan Gao🇺🇸 · Ashot Gasparian🇺🇸 · Mahbub A. Khandaker🇺🇸 · Nilanga Liyanage🇺🇸 · Eugene Pasyuk🇺🇸 · Chao Peng🇺🇸 · Weizhi Xiong🇺🇸

    Extracting the proton charge radius from electron scattering data requires determining the slope of the charge form factor at $Q^2$ of zero. But as experimental data never reach that limit, numerous methods for making the extraction have been proposed, though often the functions are determined after seeing the data which can lead to confirmation bias. To find functional forms that will allow for a robust extraction of the input radius for a wide variety of functional forms in order to have confidence in the extraction from upcoming low $Q^2$ experimental data such as the Jefferson Lab PRad experiment, we create a general framework for inputting form-factor functions as well as various fitting functions. The input form factors are used to generate pseudo-data with fluctuations intended to mimic the binning and random uncertainty of a given set of real data. All combinations of input functions and fit functions can then be tested repeatedly against regenerated pseudo-data. Since the input radius is known, this allows us to find fit functions that are robust for radius extractions in an objective fashion. For the range and uncertainty of the PRad data, we find that a two-parameter rational function, a two-parameter continued fraction and the second order polynomial expansion of $z$ can extract the input radius regardless of the input charge form factor function that is used. We have created an easily expandable framework to search for functional forms that allow for a robust extraction of the radius from a given binning and uncertainty of pseudo-data generated from a wide variety of trial functions. This method has enabled a successful search for the best functional forms to extract the radius from the upcoming PRad data and can be used for other experiments.

    ↳ nucl-exhep-phnucl-thPRC(2018)·46 citations
30. 30*

    (3+1)-dimensional anisotropic fluid dynamics with a lattice QCD equation of state

    M. McNelis🇺🇸 · D. Bazow🇺🇸 · U. Heinz🇺🇸

    Anisotropic hydrodynamics improves upon standard dissipative fluid dynamics by treating certain large dissipative corrections non-perturbatively. Relativistic heavy-ion collisions feature two such large dissipative effects: (i) Strongly anisotropic expansion generates a large shear stress component which manifests itself in very different longitudinal and transverse pressures, especially at early times. (ii) Critical fluctuations near the quark-hadron phase transition lead to a large bulk viscous pressure on the conversion surface between hydrodynamics and a microscopic hadronic cascade description of the final collision stage. We present a new dissipative hydrodynamic formulation for non-conformal fluids where both of these effects are treated nonperturbatively. The evolution equations are derived from the Boltzmann equation in the 14-moment approximation, using an expansion around an anisotropic leading-order distribution function with two momentum-space deformation parameters, accounting for the longitudinal and transverse pressures. To obtain their evolution we impose generalized Landau matching conditions for the longitudinal and transverse pressures. We describe an approximate anisotropic equation of state that relates the anisotropy parameters with the macroscopic pressures. Residual shear stresses are smaller and are treated perturbatively, as in standard second-order dissipative fluid dynamics. The resulting optimized viscous anisotropic hydrodynamic evolution equations are derived in 3+1 dimensions and tested in a (0+1)-dimensional Bjorken expansion, using a state-of-the-art lattice equation of state. Comparisons with other viscous hydrodynamical frameworks are presented.

    ↳ nucl-thhep-phPRC(2018)·34 citations
31. 31*

    Centrality fluctuations in heavy-ion collisions

    Mingliang Zhou🇺🇸 · Jiangyong Jia🇺🇸

    Volume or centrality fluctuations (CF) is one of the main uncertainties for interpreting the centrality dependence of many experimental observables. The CF is constrained by centrality selection based on particle multiplicity in a reference subevent, and contributes to observables measured in another subevent. Using a Glauber-based independent source model, we study the influence of CF on several distributions of multiplicity $N$ and eccentricities ${ϵ}_n$: $p(N)$, $p({ϵ}_n)$, $p({ϵ}_n,{ϵ}_m)$ and $p(N,{ϵ}_n)$, where the effects of CF is quantified using multi-particle cumulants of these distributions. In mid-central collisions, a general relation is established between the multiplicity fluctuation and resulting CF in the reference subevent. In ultra-central collisions, where distribution of particle production sources is strongly distorted, we find these cumulants exhibit rich sign-change patterns, due to observable-dependent non-Gaussianity in the underlying distributions. The details of sign-change pattern change with the size of the collision systems. Simultaneous comparison of these different types cumulants between model prediction and experimental data can be used to constrain the CF and particle production mechanism in heavy-ion collisions. Since the concept of centrality and CF are expected to fluctuate in the longitudinal direction within a single event, we propose to use pseudorapidity-separated subevent cumulant method to explore the nature of intra-event fluctuations of centrality and collective dynamics. The subevent method can be applied for any bulk observable that is sensitive to centrality, and has the potential to separate different mechanisms for multiplicity and flow fluctuations happening at different time scales. The forward detector upgrades at RHIC and LHC will greatly enhance such studies in the future.

    ↳ nucl-thhep-phnucl-exPRC(2018)·48 citations
32. 32*

    Phases of dense matter in compact stars

    David Blaschke🇵🇱 · Nicolas Chamel🇧🇪

    Formed in the aftermath of gravitational core-collapse supernova explosions, neutron stars are unique cosmic laboratories for probing the properties of matter under extreme conditions that cannot be reproduced in terrestrial laboratories. The interior of a neutron star, endowed with the highest magnetic fields known and with densities spanning about ten orders of magnitude from the surface to the centre, is predicted to exhibit various phases of dense strongly interacting matter, whose physics is reviewed in this chapter. The outer layers of a neutron star consist of a solid nuclear crust, permeated by a neutron ocean in its densest region, possibly on top of a nuclear "pasta" mantle. The properties of these layers and of the homogeneous isospin asymmetric nuclear matter beneath constituting the outer core may still be constrained by terrestrial experiments. The inner core of highly degenerate, strongly interacting matter poses a few puzzles and questions which are reviewed here together with perspectives for their resolution. Consequences of the dense-matter phases for observables such the neutron-star mass-radius relationship and the prospects to uncover their structure with modern observational programmes are touched upon.

    ↳ nucl-thastro-ph.HEhep-phAstrophys.Space Sci.Libr.(2018)·96 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.