Thu·Aug 8, 2019Thursday·August 8, 2019

1. 01*

   A frequentist analysis of three right-handed neutrinos with GAMBIT

   Marcin Chrzaszcz🇵🇱 · Marco Drewes🇧🇪 · Tomas E. Gonzalo🇦🇺 · Julia Harz🇩🇪 · Suraj Krishnamurthy🇳🇱 · Christoph Weniger🇳🇱

   The extension of the Standard Model by right-handed neutrinos can not only explain the active neutrino masses via the seesaw mechanism, it is also able solve a number of long standing problems in cosmology. Especially, masses below the TeV scale are of particular interest as they can lead to a plethora of signatures in experimental searches. We present the first full frequentist analysis of the extension of the Standard Model by three right-handed neutrinos, with masses between 60 MeV and 500 GeV, using the Global and Modular BSM (beyond the Standard Model) Inference Tool GAMBIT. Our analysis is based on the Casas-Ibarra parametrisation and includes a large range of experimental constraints: active neutrino mixing, indirect constraints from, e.g., electroweak precision observables and lepton universality, and numerous direct searches for right-handed neutrinos. To study their overall effect, we derive combined profile likelihood results for the phenomenologically most relevant parameter projections. Furthermore, we discuss the role of (marginally) statistically preferred regions in the parameter space. Finally, we explore the flavour mixing pattern of the three right-handed neutrinos for different values of the lightest neutrino mass. Our results comprise the most comprehensive assessment of the model with three right-handed neutrinos model below the TeV scale so far, and provide a robust ground for exploring the impact of future constraints or detections.

   hep-phhep-exEPJC(2020)·111 citations
2. 02*

   Further tests of lepton flavour universality from the charged lepton energy distribution in $b\to c$ semileptonic decays: The case of ${\Lambda }_b\to {\Lambda }_c\ell {\bar{\nu }}_{\ell }$

   Neus Penalva🇪🇸 · Eliecer Hernández🇪🇸 · Juan Nieves🇪🇸

   In a general framework, valid for any $H\to H^{\prime }{\ell }^{-}{\bar{\nu }}_{\ell }$ semileptonic decay, we analyze the $d^2\Gamma /(d\omega d\cos {\theta }_{\ell })$ and $d^2\Gamma /(d\omega d{E}_{\ell })$ distributions, with $\omega$ being the product of the hadron four-velocities, ${\theta }_{\ell }$ the angle made by the three-momenta of the charged lepton and the final hadron in the $W^{-}$ center of mass frame and $E_{\ell }$ the charged lepton energy in the decaying hadron rest frame. Within the Standard Model (SM), $d^2\Gamma /(d\omega d{E}_{\ell })\propto \left(c_0(\omega )+c_1(\omega )E_{\ell }/M+c_2(\omega )E_{\ell }^2/M^2\right)$, with $M$ the initial hadron mass. We find that $c_2(\omega )$ is independent of the lepton flavor and thus it is an ideal candidate to look for lepton flavor universality (LFU) violations. We also find a correlation between the $a_2(\omega )$ structure function, that governs the $(\cos {\theta }_{\ell }{)}^2$ dependence of $d^2\Gamma /(d\omega d\cos {\theta }_{\ell })$, and $c_2(\omega )$. Apart from trivial kinematical and mass factors, the ratio of $a_2(\omega )/c_2(\omega )$ is a universal function that can be measured in any semileptonic decay, involving not only $b\to c$ transitions. These two SM predictions can be used as new tests in the present search for signatures of LFU violations. We also generalize the formalism to account for some new physics (NP) terms. Finally, in order to illustrate our findings, we apply our general framework to the ${\Lambda }_b\to {\Lambda }_c\ell {\bar{\nu }}_{\ell }$ decay. We show that a measurement of $c_2$ (or $a_2$) for $\tau$ decay would not only be a direct measurement of the possible existence of NP, but it would also allow to distinguish from NP fits to $b\to c\tau {\bar{\nu }}_{\tau }$ anomalies in the meson sector, that otherwise give the same total and differential $d\Gamma /d\omega$ widths.

   hep-phhep-exnucl-thPRD(2019)·36 citations
3. 03*

   Valence-quark distributions of pions and kaons in a nuclear medium

   Parada T. P. Hutauruk🇰🇷 · J. J. Cobos-Martinez🇲🇽 · Yongseok Oh🇰🇷 · K. Tsushima🇧🇷

   In-medium valence-quark distributions of ${\pi }^{+}$ and $K^{+}$ mesons in symmetric nuclear matter are studied by combining the Nambu--Jona-Lasinio model and the quark-meson coupling model. The in-medium properties of the current quarks, which are used as inputs for studying the in-medium pion and kaon properties in the Nambu--Jona-Lasinio model, are calculated within the quark-meson coupling model. The light-quark condensates, light-quark dynamical masses, pion and kaon decay constants, and pion- and kaon-quark coupling constants are found to decrease as nuclear density increases. The obtained valence quark distributions in vacuum for both the ${\pi }^{+}$ and $K^{+}$ could reasonably describe the available experimental data over a wide range of Bjorken-$x$. The in-medium valence $u$-quark distribution in the ${\pi }^{+}$ at $Q^2=16\text{mbox}{GeV}^2$ is found to be almost unchanged compared to the in-vacuum case. However, the in-medium to in-vacuum ratios of both the valence $u$-quark and valence $s$-quark distributions of the $K^{+}$ meson at $Q^2=16\text{mbox}{GeV}^2$ increase with nuclear matter density, but show different $x$-dependence. Namely, the ratio for the valence $u$-quark distribution increases with $x$, while that for the valence $s$ quark decreases with $x$. These features are enhanced at higher density regions.

   hep-phnucl-thPRD(2019)·24 citations
4. 04*

   Statistical analysis of the azimuthal asymmetry in the $J/\psi$ leptoproduction in unpolarized $ep$ collisions

   Hong-Fei Zhang🇨🇳 · Wen-Long Sang🇨🇳 · Yu-Peng Yan🇹🇭

   In this paper, we study the azimuthal asymmetry in the $J/\psi$ leptoproduction in unpolarized $ep$ collisions. There are two independent azimuthal asymmetry modulations, namely $\cos (\psi )$ and $\cos (2\psi )$, where $\psi$ is the azimuthal angle of the lepton scattering plane with respect to the hadron-interacting plane. We calculate the two modulations as functions of four kinematic variables, and find that they provide a very good laboratory to distinguish several models describing the heavy quarkonium production, including the color-singlet (CS) model, the nonrelativistic QCD (NRQCD) associated with the ${}^1{S}_0^{[8]}$ dominance picture, and the NRQCD in which the values of all the three color-octet (CO) long-distance matrix elements are of the same order. In order to make definite conclusions, we restrict our calculation in a specific kinematic region, where the CS and CO mechanisms can be distinguished by scrutinizing the values of the $\cos (\psi )$ modulation, while the ${}^1{S}_0^{[8]}$ dominance picture can be tested by measuring the values of the $\cos (2\psi )$ modulation. Calculating their values and carrying out a meticulous statistical analysis, we find that at an integrated luminosity $\mathcal{L}=1000{\mathrm{pb}}^{-1}$, the statistical uncertainties of the two quantities are small enough to tell the three models apart. When this experiment is implemented at the future $ep$ colliders such as the EIC, crucial information for the $J/\psi$ production mechanism might be discovered.

   hep-phhep-exJHEP(2019)·6 citations
5. 05*

   Multi-Quark Colour Decompositions from Unitarity

   Alexander Ochirov🇨🇭 · Ben Page🇫🇷

   Any loop QCD amplitude at full colour is constructed from kinematic and gauge-group building blocks. In a unitarity-based on-shell framework, both objects can be reconstructed from their respective counterparts in tree-level amplitudes. This procedure is at its most powerful when aligned with flexible colour decompositions of tree-level QCD amplitudes. In this note we derive such decompositions for amplitudes with an arbitrary number of quarks and gluons from the same principle that is used to bootstrap kinematics - unitarity factorisation. In the process we formulate new multi-quark bases and provide closed-form expressions for the new decompositions. We then elaborate upon their application in colour decompositions of loop multi-quark amplitudes.

   hep-phhep-thJHEP(2019)·42 citations
6. 06*

   Dark Matter, Dark Radiation and Gravitational Waves from Mirror Higgs Parity

   David Dunsky🇺🇸 · Lawrence J. Hall🇺🇸 · Keisuke Harigaya🇺🇸

   An exact parity replicates the Standard Model giving a Mirror Standard Model, SM $\leftrightarrow$ SM${}^{\prime }$. This "Higgs Parity" and the mirror electroweak symmetry are spontaneously broken by the mirror Higgs, $⟨H^{\prime }⟩=v^{\prime }\gg ⟨H⟩$, yielding the Standard Model Higgs as a Pseudo-Nambu-Goldstone Boson of an approximate $SU(4)$ symmetry, with a quartic coupling ${\lambda }_{SM}(v^{\prime })\sim 10^{-3}$. Mirror electromagnetism is unbroken and dark matter is composed of $e^{\prime }$ and ${\bar{e}}^{\prime }$. Direct detection may be possible via the kinetic mixing portal, and in unified theories this rate is correlated with the proton decay rate. With a high reheat temperature after inflation, the $e^{\prime }$ dark matter abundance is determined by freeze-out followed by dilution from decays of mirror neutrinos, ${\nu }^{\prime }\to \ell H$. Remarkably, this requires $v^{\prime }\sim (10^8-10^{10})$ GeV, consistent with the Higgs mass, and a Standard Model neutrino mass of $(10^{-2}-10^{-1})$ eV, consistent with observed neutrino masses. The mirror QCD sector exhibits a first order phase transition producing gravitational waves that may be detected by future observations. Mirror glueballs decay to mirror photons giving dark radiation with $\Delta N_{\mathrm{eff}}\sim 0.03-0.4$. With a low reheat temperature after inflation, the $e^{\prime }$ dark matter abundance is determined by freeze-in from the SM sector by either the Higgs or kinetic mixing portal.

   hep-phastro-ph.COJHEP(2020)·42 citations
7. 07*

   DoFun 3.0: Functional equations in Mathematica

   Markus Q. Huber🇩🇪 · Anton K. Cyrol🇩🇪 · Jan M. Pawlowski🇩🇪

   We present version 3.0 of the Mathematica package DoFun for the derivation of functional equations. In this version, the derivation of equations for correlation functions of composite operators was added. In the update, the general workflow was slightly modified taking into account experience with the previous version. In addition, various tools were included to improve the usage experience and the code was partially restructured for easier maintenance.

   hep-phcond-mat.otherhep-thComput.Phys.Commun.(2020)·54 citations
8. 08*

   Trimaximal TM${}_1$ mixing with two modular $S_4$ groups

   Stephen F. King🇬🇧 · Ye-Ling Zhou🇬🇧

   We discuss a minimal flavour model with twin modular symmetries, leading to trimaximal TM${}_1$ lepton mixing in which the first column of the tri-bimaximal lepton mixing matrix is preserved. The model involves two modular $S_4$ groups, one acting in the neutrino sector, associated with a modulus field value ${\tau }_{SU}$ with residual $Z_2^{SU}$ symmetry, and one acting in the charged lepton sector, associated with a modulus field value ${\tau }_T$ with residual $Z_3^T$ symmetry. Apart from the predictions of TM${}_1$ mixing, the model leads to a new neutrino mass sum rule which implies lower bounds on neutrino masses close to current limits from neutrinoless double beta decay experiments and cosmology.

   hep-phPRD(2020)·143 citations
9. 09*

   Detecting and Studying High-Energy Collider Neutrinos with FASER at the LHC

   FASER Collaboration: Henso Abreu🇮🇱 · Claire Antel🇨🇭 · Akitaka Ariga🇨🇭 · Tomoko Ariga🇨🇭 · Jamie Boyd🇨🇭 · Franck Cadoux🇨🇭 · David W. Casper🇺🇸 · Xin Chen🇨🇳 · Andrea Coccaro🇮🇹 · Candan Dozen🇨🇳 · Peter B. Denton🇺🇸 · Yannick Favre🇨🇭 and 35 other authors

   Neutrinos are copiously produced at particle colliders, but no collider neutrino has ever been detected. Colliders, and particularly hadron colliders, produce both neutrinos and anti-neutrinos of all flavors at very high energies, and they are therefore highly complementary to those from other sources. FASER, the recently approved Forward Search Experiment at the Large Hadron Collider, is ideally located to provide the first detection and study of collider neutrinos. We investigate the prospects for neutrino studies of a proposed component of FASER, FASER$\nu$, a 25cm x 25cm x 1.35m emulsion detector to be placed directly in front of the FASER spectrometer in tunnel TI12. FASER$\nu$ consists of 1000 layers of emulsion films interleaved with 1-mm-thick tungsten plates, with a total tungsten target mass of 1.2 tons. We estimate the neutrino fluxes and interaction rates at FASER$\nu$, describe the FASER$\nu$ detector, and analyze the characteristics of the signals and primary backgrounds. For an integrated luminosity of 150 fb${}^{-1}$ to be collected during Run 3 of the 14 TeV Large Hadron Collider from 2021-23, and assuming standard model cross sections, approximately 1300 electron neutrinos, 20,000 muon neutrinos, and 20 tau neutrinos will interact in FASER$\nu$, with mean energies of 600 GeV to 1 TeV, depending on the flavor. With such rates and energies, FASER will measure neutrino cross sections at energies where they are currently unconstrained, will bound models of forward particle production, and could open a new window on physics beyond the standard model.

   ↳ hep-exhep-phphysics.ins-detEPJC(2020)·248 citations
10. 10*

    Coulomb expectation values in $D=3$ and $D=3-2ϵ$ dimensions

    Gregory S. Adkins🇺🇸 · Md Faisal Alam🇺🇸 · Conor Larison🇺🇸 · Ruosi Sun🇺🇸

    We explore the quantum Coulomb problem for two-body bound states, in $D=3$ and $D=3-2ϵ$ dimensions, in detail, and give an extensive list of expectation values that arise in the evaluation of QED corrections to bound state energies. We describe the techniques used to obtain these expectation values and give general formulas for the evaluation of integrals involving associated Laguerre polynomials. In addition, we give formulas for the evaluation of integrals involving subtracted associated Laguerre polynomials--those with low powers of the variable subtracted off--that arise when evaluating divergent expectation values. We present perturbative results (in the parameter $ϵ$) that show how bound state energies and wave functions in $D=3-2ϵ$ dimensions differ from their $D=3$ dimensional counterparts and use these formulas to find regularized expressions for divergent expectation values such as $⟨{\bar{V}}^3⟩$ and $⟨({\bar{V}}^{\prime }{)}^2⟩$ where $\bar{V}$ is the $D$-dimensional Coulomb potential. We evaluate a number of finite $D$-dimensional expectation values such as $⟨r^{-2+4ϵ}{\partial }_r^2⟩$ and $⟨r^{4ϵ}{p}^4⟩$ that have $ϵ\to 0$ limits that differ from their three-dimensional counterparts $⟨r^{-2}{\partial }_r^2⟩$ and $⟨p^4⟩$. We explore the use of recursion relations, the Feynman-Hellmann theorem, and momentum space brackets combined with $D$-dimensional Fourier transformation for the evaluation of $D$-dimensional expectation values. The results of this paper are useful when using dimensional regularization in the calculation of properties of Coulomb bound systems.

    ↳ quant-phhep-phPRA(2020)·9 citations
11. 11*

    Gravitational Potential from small-scale clustering in action space: Application to Gaia DR2

    Tianyi. Yang🇨🇦 · Supranta Sarma Boruah🇨🇦 · Niayesh. Afshordi🇨🇦

    Most measurements of mass in Astronomy that use kinematics of stars or gas rely on assumptions of equilibrium that are often hard to verify. Instead, we develop a novel idea that uses the clustering in action space, as a probe of underlying gravitational potential: the correct potential should maximize small-scale clustering in the action space. We provide a first-principle derivation of likelihood using the two-point correlation function in action space, and test it against simulations of stellar streams. We then apply this method to the 2nd data release of Gaia, and use it to measure the radial force fraction $f_h$ and logarithmic slope $\alpha$ of dark matter halo profile. We investigate stars within 9-11 kpc and 11.5-15 kpc from Galactic centre, and find $(f_h,\alpha )=(0.391\pm 0.009,1.835\pm 0.092)$ and $(0.351\pm 0.012,1.687\pm 0.079)$, respectively. We also confirm that the set of parameters that maximize the likelihood function do correspond to the most clustering in the action space. The best-fit circular velocity curve for Milky Way potential is consistent with past measurements (although it is $\sim$ 5-10\% lower than previous methods that use masers or globular clusters). Our work provides a clear demonstration of the full statistical power that lies in the full phase space information, relieving the need for {\it ad hoc} assumptions such as virial equilibrium, circular motion, or steam-finding algorithms.

    ↳ astro-ph.GAastro-ph.COhep-phMNRAS(2020)·5 citations
12. 12*

    Review of opportunities at the HESR-Collider with PANDA at FAIR

    Leonid Frankfurt🇮🇱 · Mark Strikman🇺🇸 · Alexei Larionov🇩🇪 · Andreas Lehrach🇩🇪 · Rudolf Maier🇩🇪 · Hendrik van Hees🇩🇪 · Christian Spieles🇩🇪 · Volodymyr Vovchenko🇩🇪 · Horst Stoecker🇩🇪

    Exciting new scientific opportunities are presented for the PANDA detector at the High Energy Storage Ring in the redefined $\overline{\text{p}}\text{p}(A)$ collider mode, HESR-C, at the Facility for Antiproton and Ion Research (FAIR) in Europe. The high luminosity, $L\sim 10^{31}$ cm${}^{-2}$ s${}^{-1}$, and a wide range of intermediate and high energies, $\sqrt{s_{\text{NN}}}$ up to 30 GeV for $\overline{\text{p}}\text{p}(A)$ collisions will allow to explore a wide range of exciting topics in QCD, including the study of the production of excited open charm and bottom states, nuclear bound states containing heavy (anti)quarks, the interplay of hard and soft physics in the dilepton production, probing short-range correlations in nuclei, and the exploration of the early, complete $\overline{\text{p}}$-p-annihilation phase, where an intially pure Yang-Mills gluon plasma is formed.

    ↳ nucl-thhep-phnucl-exEPJA(2020)·9 citations
13. 13*

    Numerical exploration of three relativistic particles in a finite volume including two-particle resonances and bound states

    Fernando Romero-López🇪🇸 · Stephen R. Sharpe🇺🇸 · Tyler D. Blanton🇺🇸 · Raúl A. Briceño🇺🇸 · Maxwell T. Hansen🇨🇭

    In this work, we use an extension of the quantization condition, given in Ref. [1], to numerically explore the finite-volume spectrum of three relativistic particles, in the case that two-particle subsets are either resonant or bound. The original form of the relativistic three-particle quantization condition was derived under a technical assumption on the two-particle K matrix that required the absence of two-particle bound states or narrow two-particle resonances. Here we describe how this restriction can be lifted in a simple way using the freedom in the definition of the K-matrix-like quantity that enters the quantization condition. With this in hand, we extend previous numerical studies of the quantization condition to explore the finite-volume signature for a variety of two- and three-particle interactions. We determine the spectrum for parameters such that the system contains both dimers (two-particle bound states) and one or more trimers (in which all three particles are bound), and also for cases where the two-particle subchannel is resonant. We also show how the quantization condition provides a tool for determining infinite-volume dimer-particle scattering amplitudes for energies below the dimer breakup. We illustrate this for a series of examples, including one that parallels physical deuteron-nucleon scattering. All calculations presented here are restricted to the case of three identical scalar particles.

    ↳ hep-latcond-mat.stat-mechhep-phnucl-th+1JHEP(2019)·102 citations
14. 14*

    Unitarity, stability and loops of unstable ghosts

    John F. Donoghue🇺🇸 · Gabriel Menezes🇧🇷

    We present a new understanding of the unstable ghost-like resonance which appears in theories such as quadratic gravity and Lee-Wick type theories. Quantum corrections make this resonance unstable, such that it does not appear in the asymptotic spectrum. We prove that these theories are unitary to all orders. Unitarity is satisfied by the inclusion of only cuts from stable states in the unitarity sum. This removes the need to consider this as a ghost state in the unitarity sum. However, we often use a narrow-width approximation where we do include cuts through unstable states, and ignore cuts through the stable decay products. If we do this with the unstable ghost resonance at one loop, we get the correct answer only by using a contour which was originally defined by Lee and Wick. The quantum effects also provide damping in both the Feynman and the retarded propagators, leading to stability under perturbations.

    ↳ hep-thgr-qchep-phPRD(2019)·180 citations
15. 15*

    Formation and evaporation of strangelets during the merger of two compact stars

    Niccolò Bucciantini (INAF, Dip. Fisica e Astronomia, INFN - Firenze)🇮🇹 · Alessandro Drago (Dip. Fisica e Scienze della Terra, INFN - Ferrara)🇮🇹 · Giuseppe Pagliara (Dip. Fisica e Scienze della Terra, INFN - Ferrara)🇮🇹 · Silvia Traversi (Dip. Fisica e Scienze della Terra, INFN - Ferrara)🇮🇹 · Andreas Bauswein (GSI, Darmstadt)🇩🇪

    We study the partial fragmentation of a strange quark star into strangelets during the process of merger of two strange quark stars. We discuss the fate of the fragments considering their possible evaporation into nucleons. We show that only a rather small amount of large size strangelets, ejected from the spiral arms in the post-merger, survives a total evaporation into nucleons. In this way we demonstrate that: 1) the density of strangelets in the galaxy is too low to trigger the conversion of all neutron stars into strange quark stars and it allows the co-existence of both types of compact objects; 2) the probability of direct detection of a strangelet is negligible and therefore its nondetection is compatible with the strange quark matter hypothesis; 3) most of the matter ejected during and after the merger of two strange quark stars evaporates into nucleons and therefore it can generate a kilonova-like signal.

    ↳ astro-ph.HEhep-phnucl-thPRD(2022)·29 citations
16. 16*

    Probing the era of reheating for reconstructed inflationary potential in the RS II braneworld

    Sukannya Bhattacharya🇮🇳 · Kumar Das🇮🇳 · Mayukh R. Gangopadhyay🇮🇳

    We analyse the epoch of reheating after an inflationary phase in the Randal Sundrum(RS) Type-$\mathrm{II}$ braneworld, where we did not consider any particular model of inflation, but rather reconstructed the inflationary potential solving the flow equations using Monte Carlo (MC) approach. It is shown numerically that a potential conceived through the MC reconstruction technique can be represented by an effective potential as a function of the number of e-foldings($N$). Then, the epoch of reheating is studied for this reconstructed potential. The relation between the reheating temperature ($T_{\mathrm{reh}}$) and the 5-dimensional Planck mass($M_5$) is established. Moreover, it is argued that there is a stringent bound on the critical reheating temperature that also translates to a tight bound on $M_5$ .

    ↳ astro-ph.COhep-phClass.Quant.Grav.(2020)·17 citations
17. 17*

    Universality of the Poincaré gravitational form factor constraints

    Cédric Lorcé🇫🇷 · Peter Lowdon🇫🇷

    Relativistic spin states are convention dependent. In this work we prove that the zero momentum-transfer limits of the leading two form factors in the decomposition of the energy-momentum tensor matrix elements are independent of this choice. In particular, we demonstrate that these constraints are insensitive to whether the corresponding states are massive or not, and that they arise purely due to the Poincaré covariance of the states.

    ↳ hep-thgr-qchep-phEPJC(2020)·27 citations
18. 18*

    Spin-polarized neutron matter, the maximum mass of neutron stars, and GW170817

    I. Tews🇺🇸 · A. Schwenk🇩🇪

    We investigate how a phase transition from neutron-star matter to spin-polarized neutron matter affects the equation of state and mass-radius relation of neutron stars. While general extension schemes for the equation of state allow for high pressures inside neutron stars, we find that a phase transition to spin-polarized neutron matter excludes extreme regimes. Hence, such a transition limits the maximum mass of neutron stars to lie below 2.6$-$$2.9M_{\odot }$, depending on the microscopic nuclear forces used, while significantly larger masses could be reached without these constraints. These limits are in good agreement with recent constraints extracted from the neutron-star merger GW170817 and its electromagnetic counterpart. Assuming the description in terms of spin-polarized neutron matter to be valid in the center of neutron stars, we find that stars with a large spin-polarized domain in their core are ruled out by GW170817.

    ↳ nucl-thastro-ph.HEastro-ph.SRhep-phApJ(2020)·18 citations
19. 19*

    A Practical Mini-Course on Applied Holography

    Matteo Baggioli🇪🇸

    This is a collection of notes based on lectures given at IIT Madras in September 2019 and at IFT Madrid in November 2019. It is supposed to be a concise (and therefore not comprehensive) and pragmatic course on applied holography and especially the (basic) analytic and numerical techniques involved. The lectures are not focused on the large theoretical and fundamental background which can be found already in several places in the literature, but rather on concrete applications of Bottom-Up AdS-CFT to Hydrodynamics, QCD and Condensed Matter. The idea is to accompany the reader step by step through the various benchmark examples with a classmate attitude, providing details of the computations and open-source numerical codes in Mathematica, and sharing simple tricks and warnings collected during my research experience. At the end of this path, the reader will be in possess of all the fundamental skills and tools to learn by himself/herself more advanced techniques and to produce independent and novel research on the topic.

    ↳ hep-thcond-mat.softcond-mat.str-elhep-phSpringerBriefs in Physics 2019·79 citations
20. 20*

    Fractional Dark Matter decay: cosmological imprints and observational constraints

    Linfeng Xiao🇨🇳 · Le Zhang🇨🇳 · Rui An🇨🇳 · Chang Feng🇺🇸 · Bin Wang🇨🇳

    If a fraction $f_{\mathrm{dcdm}}$ of the Dark Matter decays into invisible and massless particles (so-called "dark radiation") with the decay rate (or inverse lifetime) ${\Gamma }_{\mathrm{dcdm}}$, such decay will leave distinctive imprints on cosmological observables. With a full consideration of the Boltzmann hierarchy, we calculate the decay-induced impacts not only on the CMB but also on the redshift distortion and the kinetic Sunyaev-Zel'dovich effect, while providing detailed physical interpretations based on evaluating the evolution of gravitational potential. By using the current cosmological data with a combination of Planck 2015, Baryon Acoustic Oscillation and redshift distortion measurements which can improve the constraints, we update the $1\sigma$ bound on the fraction of decaying DM from $f_{\mathrm{dcdm}}\lesssim 5.26\%$ to $f_{\mathrm{dcdm}}\lesssim 2.73\%$ for the short-lived DM (assuming ${\Gamma }_{\mathrm{dcdm}}/H_0\gtrsim 10^4$). However, no constraints are improved from RSD data ($f_{\mathrm{dcdm}}\lesssim 0.94\%$) for the long-lived DM (i.e., ${\Gamma }_{\mathrm{dcdm}}/H_0\lesssim 10^4$). We also find the fractional DM decay can only slightly reduce the $H_0$ and ${\sigma }_8$ tensions, which is consistent with other previous works. Furthermore, our calculations show that the kSZ effect in future would provide a further constraining power on the decaying DM.

    ↳ astro-ph.COhep-phJCAP(2020)·39 citations
21. 21*

    Cross Section for $\gamma n\to {\pi }^{0}n$ measured at Mainz/A2

    W. J. Briscoe · M. Hadzimehmedovi · A. E. Kudryavtsev · V. V. Kulikov · M. A. Martemianov · I. I. Strakovsky · A. Svarc · V. E. Tarasov · R. L. Workman · S. Abt · P. Achenbach · C. S. Akondi and 80 other authors

    The $\gamma n\to {\pi }^{0}n$ differential cross section evaluated for 27 energy bins span the photon-energy range 290-813 MeV (W = 1.195-1.553 GeV) and the pion c.m. polar production angles, ranging from 18 deg to 162 deg, making use of model-dependent nuclear corrections to extract pi0 production data on the neutron from measurements on the deuteron target. Additionally, the total photoabsorption cross section was measured. The tagged photon beam produced by the 883-MeV electron beam of the Mainz Microtron MAMI was used for the 0-meson production. Our accumulation of 3.6 x 10^6 $\gamma n\to {\pi }^{0}n$ events allowed a detailed study of the reaction dynamics. Our data are in reasonable agreement with previous A2 measurements and extend them to lower energies. The data are compared to predictions of previous SAID, MAID, and BnGa partial-wave analyses and to the latest SAID fit MA19 that included our data. Selected photon decay amplitudes $N^{\ast }\to \gamma n$ at the resonance poles are determined for the first time.

    ↳ nucl-exhep-exhep-phnucl-thPRC(2019)·39 citations
22. 22*

    Dissipation triggers dynamical two-stream instability

    Nils Andersson🇬🇧 · Andreas Schmitt🇬🇧

    Two coupled, interpenetrating fluids suffer instabilities beyond certain critical counterflows. For ideal fluids, an energetic instability occurs at the point where a sound mode inverts its direction due to the counterflow, while dynamical instabilities only occur at larger relative velocities. Here we discuss two relativistic fluids, one of which is dissipative. Using linearized hydrodynamics, we show that in this case the energetic instability turns dynamical, i.e., there is an exponentially growing mode, and this exponential growth only occurs in the presence of dissipation. This result is general and does not rely on an underlying microscopic theory. It can be applied to various two-fluid systems for instance in the interior of neutron stars. We also point out that under certain circumstances the two-fluid system exhibits a mode analogous to the r-mode in neutron stars that can become unstable for arbitrarily small values of the counterflow.

    ↳ gr-qcastro-ph.HEhep-phphysics.plasm-phParticles(2019)·8 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.