Fri·Sep 6, 2019Friday·September 6, 2019

1. 01*

   Higgsstrahlung at NNLL${}^{\prime }+$NNLO Matched to Parton Showers in GENEVA

   Simone Alioli🇮🇹 · Alessandro Broggio🇮🇹 · Stefan Kallweit🇮🇹 · Matthew A. Lim🇮🇹 · Luca Rottoli🇮🇹

   We present results for the Higgsstrahlung process within the GENEVA Monte Carlo framework. We combine the fully differential NNLO calculation with the higher-order resummation in the 0-jettiness resolution variable (beam-thrust). The resulting parton-level events are further showered and hadronised by Pythia8. The beam-thrust resummation is carried out to NNLL${}^{\prime }$ accuracy, which consistently incorporates all singular virtual and real NNLO corrections. It thus provides a natural perturbative connection between the NNLO calculation and the parton shower regime, including a systematic assessment of perturbative uncertainties. In this way, observables which are inclusive over the additional radiation are correct to NNLO, while the description of 0-jet-like resummation variables is improved beyond the parton shower approximation. We provide predictions for the 13 TeV LHC.

   hep-phhep-exPRD(2019)·78 citations
2. 02*

   The Majoron at two loops

   Julian Heeck🇺🇸 · Hiren H. Patel🇺🇸

   We present singlet-Majoron couplings to Standard Model particles through two loops at leading order in the seesaw expansion, including couplings to gauge bosons as well as flavor-changing quark interactions. We discuss and compare the relevant phenomenological constraints on Majoron production as well as decaying Majoron dark matter. A comparison with standard seesaw observables in low-scale settings highlights the importance of searches for lepton-flavor-violating two-body decays $\ell \to {\ell }^{\prime }+$Majoron in both the muon and tau sectors.

   hep-phPRD(2019)·90 citations
3. 03*

   Quark-diquark models and baryonic fluctuations in QCD

   E. Megias🇪🇸 · E. Ruiz Arriola🇪🇸 · L.L. Salcedo🇪🇸

   We study the baryonic fluctuations of electric charge, baryon number and strangeness, by considering a realization of the Hadron Resonance Gas model in the light flavor sector of QCD. We elaborate on the idea that the susceptibilities can be saturated with excited baryonic states with a quark-diquark structure with a linearly confining interaction identical up to a constant to the quark-antiquark potential, $V_{qD}^{\prime }(r)=V_{q\bar{q}}^{\prime }(r)$. We obtain an overall good agreement with the spectrum obtained with other quark models and with lattice data for the fluctuations.

   hep-phhep-latnucl-thNucl.Part.Phys.Proc.(2020)·0 citations
4. 04*

   Higgs Troika for Baryon Asymmetry

   Hooman Davoudiasl🇺🇸 · Ian M. Lewis🇺🇸 · Matthew Sullivan🇺🇸

   To explain the baryon asymmetry of the Universe, we extend the Standard Model (SM) with two additional Higgs doublets with small vacuum expectation values. The additional Higgs fields interact with SM fermions through complex Yukawa couplings, leading to new sources of CP violation. We propose a simple flavor model with $\mathcal{O}(1)$ or less Yukawa couplings for quarks and charged leptons, consistent with current flavor constraints. To generate neutrino masses and the baryon asymmetry, right-handed neutrinos in the $\sim 0.1-10$ TeV range couple to the "Higgs Troika." The new Higgs doublet masses could be near the TeV scale, allowing for asymmetric decays into Standard Model lepton doublets and right-handed neutrinos. The asymmetry in lepton doublets is then processed into a baryon asymmetry, similar to leptogenesis. Since the masses of the new fields are near the TeV scale, there is potentially a rich high energy collider phenomenology, including observable deviations in the 125 GeV Higgs decay into muons and taus, as well as detectable low energy signals such as the electron EDM or $\mu \to e\gamma$. Hence, this is in principle a testable model for generation of baryon asymmetry, similar in that respect to "electroweak baryogenesis."

   hep-phhep-exPRD(2020)·15 citations
5. 05*

   Correlating ${ϵ}^{\prime }/ϵ$ to hadronic $B$ decays via $U(2{)}^3$ flavour symmetry

   Andreas Crivellin🇨🇭 · Christian Gross🇮🇹 · Stefan Pokorski🇵🇱 · Leonardo Vernazza🇳🇱

   There are strong similarities between charge-parity (CP) violating observables in hadronic $B$ decays (in particular $\Delta A_{\mathrm{CP}}^{-}$ in $B\to K\pi$) and direct CP violation in Kaon decays (${ϵ}^{\prime }$): All these observables are very sensitive to new physics (NP) which is at the same time CP and isospin violating (i.e. NP with complex couplings which are different for up quarks and down quarks). Intriguingly, both the measurements of ${ϵ}^{\prime }$ and $\Delta A_{\mathrm{CP}}^{-}$ show deviations from their Standard Model predictions, calling for a common explanation (the latter is known as the $B\to K\pi$ puzzle). For addressing this point, we parametrize NP using a gauge invariant effective field theory approach combined with a global $U(2{)}^3$ flavor symmetry in the quark sector (also known as less-minimal flavour violation). We first determine the operators which can provide a common explanation of ${ϵ}^{\prime }$ and $\Delta A_{\mathrm{CP}}^{-}$ and then perform a global fit of their Wilson coefficients to the data from hadronic $B$ decays. Here we also include e.g. the recently measured CP asymmetry in $B_s\to KK$ as well as the purely isospin violating decay $B_s\to \varphi {\rho }^0$, finding a consistent NP pattern providing a very good fit to data. Furthermore, we can at the same time explain ${ϵ}^{\prime }/ϵ$ for natural values of the free parameters within our $U(2{)}^3$ flavour approach, and this symmetry gives interesting predictions for hadronic decays involving $b\to d$ transitions.

   hep-phPRD(2020)·12 citations
6. 06*

   Phenomenology of the new light Higgs bosons in Gildener-Weinberg model

   Kenneth Lane🇺🇸 · Eric Pilon🇫🇷

   Gildener-Weinberg (GW) models of electroweak symmetry breaking are especially interesting because the low mass and nearly Standard Model couplings of the $125\mathrm{GeV}$ Higgs boson, $H$, are protected by approximate scale symmetry. Another important but so far under-appreciated feature of these models is that a sum rule bounds the masses of the new charged and neutral Higgs bosons appearing in {\em all} these models to be below about $500\mathrm{GeV}$. Therefore, they are within reach of LHC data currently or soon to be in hand. Also so far unnoticed of these models, certain cubic and quartic Higgs scalar couplings vanish at the classical level. This is due to spontaneous breaking of the scale symmetry. These couplings become nonzero from explicit scale breaking in the Coleman-Weinberg loop expansion of the effective potential. In a two-Higgs doublet GW model, we calculate ${\lambda }_{HHH}\simeq 2({\lambda }_{HHH}{)}_{\mathrm{SM}}=64\mathrm{GeV}$. This corresponds to $\sigma (pp\to HH)\cong 15$--$20\mathrm{fb}$, its {\em minimum} value for $\sqrt{s}=13$--$14\mathrm{TeV}$ at the LHC. It will require at least the $27\mathrm{TeV}$ HE-LHC to observe this cross section. We also find ${\lambda }_{HHHH}\simeq 4({\lambda }_{HHHH}{)}_{\mathrm{SM}}=0.129$, whose observation in $pp\to HHH$ requires a $100\mathrm{TeV}$ collider. Because of the above-mentioned sum rule, these results apply to {\em all} GW models. In view of this unpromising forecast, we stress that LHC searches for the new relatively light Higgs bosons of GW models are by far the surest way to test them in this decade.

   hep-phPRD(2020)·19 citations
7. 07*

   Heavy-quark exotics

   Jonathan L. Rosner🇺🇸

   The heavy quarks $c$ and $b$ stabilize exotic meson $(qq\bar{q}\bar{q})$ and baryon $(qqqq\bar{q})$ states. We discuss work with M. Karliner on molecules containing $c\bar{c}$ and $b\bar{b}$; the first doubly charmed baryon; isospin splittings; ${\Xi }_{cc}^{+}=ccd$ and ${\Omega }_{cc}=ccs$ masses; lifetimes; tetraquarks stable under strong and electromagnetic decay; excited ${\Omega }_c$ states; and P-wave excitation energies.

   hep-phhep-ex0 citations
8. 08*

   Predicting the SUSY breaking scale in SUGRA models with degenerate vacua

   C. D. Froggatt🇬🇧 · R. Nevzorov🇷🇺 · H. B. Nielsen🇩🇰 · A. W. Thomas🇦🇺

   In N=1 supergravity the scalar potential may have supersymmetric (SUSY) and non-supersymmetric Minkowski vacua (associated with supersymmetric and physical phases) with vanishing energy density. In the supersymmetric Minkowski (second) phase some breakdown of SUSY may be induced by non-perturbative effects in the observable sector that give rise to a tiny positive vacuum energy density. Postulating the exact degeneracy of the physical and second vacua as well as assuming that at high energies the couplings in both phases are almost identical, one can estimate the dark energy density in these vacua. It is mostly determined by the SUSY breaking scale M_S in the physical phase. Exploring the two-loop renormalization group (RG) flow of couplings in these vacua we find that the measured value of the cosmological constant can be reproduced if M_S varies from 20 TeV to 400 TeV. We also argue that this prediction for the SUSY breaking scale is consistent with the upper bound on M_S in the higgsino dark matter scenario.

   hep-phhep-thInt.J.Mod.Phys.A(2020)·2 citations
9. 09*

   Elliptic and triangular flows in dAu collisions at 200 GeV in the fusing color string model

   M.A. Braun🇷🇺 · C. Pajares🇪🇸

   In the color string picture with fusion and percolation the elliptic and triangular flows are studied for p-Au and d-Au collisions at 200 GeV. The ordering $v_n(d-Au)>v_n(p-Au)$ observed experimentally for central collisions is reproduced.The calculated elliptic flow $v_2$ at central collisions agrees satisfactorily with thedata. The triangular flow $v_3$ is found to be greater than the experimental values, similar to the resultsobtained in the approach based on the Color Glass Condensate initial conditions with subsequenthydrodynamical evolution.

   hep-phnucl-thEPJA(2020)·3 citations
10. 10*

    Chiral phase transition in the linear sigma model within Hartree factorization in the Tsallis nonextensive statistics

    Masamichi Ishihara🇯🇵

    We studied chiral phase transition in the linear sigma model within the Tsallis nonextensive statistics in the case of small deviation from the Boltzmann-Gibbs (BG) statistics. The statistics has two parameters: the temperature $T$ and the entropic parameter $q$. The normalized $q$-expectation value and the physical temperature $\text{Tph}$ were employed in this study. The normalized $q$-expectation value was expanded as a series of the value $(1-q)$, where the absolute value $|1-q|$ is the measure of the deviation from the BG statistics. We applied the Hartree factorization and the free particle approximation, and obtained the equations for the condensate, the sigma mass, and the pion mass. The physical temperature dependences of these quantities were obtained numerically. We found following facts. The condensate at $q$ is smaller than that at $q^{\prime }$ for $q>q^{\prime }$. The sigma mass at $q$ is lighter than that at $q^{\prime }$ for $q>q^{\prime }$ at low physical temperature, and the sigma mass at $q$ is heavier than that at $q^{\prime }$ for $q>q^{\prime }$ at high physical temperature. The pion mass at $q$ is heavier than that at $q^{\prime }$ for $q>q^{\prime }$. The difference between the pion masses at different values of $q$ is small for $\text{Tph}\le 200$ MeV. That is to say, the condensate and the sigma mass are affected by the Tsallis nonextensive statistics of small $|1-q|$, and the pion mass is also affected by the statistics of small $|1-q|$ except for $\text{Tph}\le 200$ MeV.

    hep-phEPJA(2020)·3 citations
11. 11*

    Critical point signatures in the cluster expansion in fugacities

    Volodymyr Vovchenko🇩🇪 · Carsten Greiner🇩🇪 · Volker Koch🇺🇸 · Horst Stoecker🇩🇪

    The QCD baryon number density can formally be expanded into a Laurent series in fugacity, which is a relativistic generalization of Mayer's cluster expansion. We determine properties of the cluster expansion in a model with a phase transition and a critical point at finite baryon density, in which the Fourier coefficients of the expansion can be determined explicitly and to arbitrary order. The asymptotic behavior of Fourier coefficients changes qualitatively as one traverses the critical temperature and it is connected to the branch points of a thermodynamic potential associated with the phase transition. The results are discussed in the context of lattice QCD simulations at imaginary chemical potential. We argue that the location of a branch point closest to the imaginary chemical potential axis can be extracted through an analysis of an exponential suppression of Fourier coefficients. This is illustrated using the four leading coefficients both in a toy model as well as by using recent lattice QCD data.

    hep-phhep-latnucl-thPRD(2020)·10 citations
12. 12*

    Inclusion of the ${}^3{P}_0$ model in PYTHIA 8

    Albi Kerbizi🇮🇹 · Leif Lönnblad🇸🇪

    The spin effects in the hadronization process have been included for the first time in the PYTHIA 8 event generator. The spin effects are limited to the production of pseudo-scalar mesons and are obtained from the propagation of the quark polarization along the fragmentation chain according to the rules of the so-called ${}^3{P}_0$ model. The interface between PYTHIA 8 and the package of the ${}^3{P}_0$ model is presented together with preliminary results on the Collins and di-hadron asymmetries as obtained from simulations of the transversely polarized semi-inclusive deep inelastic scattering process.

    hep-phPoS(2019)·5 citations
13. 13*

    Searching for Dark Photons at the LHeC and FCC-he

    Monica D'Onofrio🇬🇧 · Oliver Fischer🇩🇪 · Zeren Simon Wang🇰🇷

    Extensions of the Standard Model (SM) gauge group with a new $U(1{)}_X$ predict an additional gauge boson. Through kinetic mixing with the SM photons featured by a coupling $ϵ$, the ensuing so-called dark photons ${\gamma }^{\prime }$, which acquire mass as a result of the breaking of the gauge group $U(1{)}_X$, can interact with the SM field content. These massive dark photons can therefore decay to pairs of leptons, hadrons, or quarks, depending on their mass $m_{{\gamma }^{\prime }}$. In this work, we discuss searches for dark photons in the mass range around and below one GeV at the LHeC and FCC-he colliders. The signal is given by the displaced decays of the long-lived dark photon into two charged fermions. We discuss the impact of conceivable irreducible (SM and machine-related) backgrounds and different signal efficiencies. Our estimates show that the LHeC and FCC-he can test a domain that is complementary to other present and planned experiments.

    hep-phPRD(2020)·34 citations
14. 14*

    Mono-b events from single stop production at the HL-LHC and HE-LHC

    Tian-Peng Tang🇨🇳 · Ning Liu🇨🇳 · Hang Zhou🇨🇳

    Top-squarks (stop) play an important role in SUSY naturalness. The stop pair production is considered as the most effective way to search for stop at the LHC. However, the collider signature of stop pair production is usually characterized by $t\bar{t}$ plus missing transverse energy, which is also predicted in many other non-supersymmetric models. On the other hand, the single stop production via the electroweak interaction can provide some distinctive signatures, and thus will help to confirm the existence of the stop. In this paper, we investigate the observability of the mono-$b$ events from the single stop production process $pp\to {\tilde{t}}_1{\tilde{\chi }}_1^{-}\to b+E{/}_T$ in a simplified MSSM framework where the higgsinos and stops are the only sparticles at the HL-LHC and HE-LHC. We find that the stop mass and the higgsino mass may be probed up to about 1.6 TeV and 550 GeV at $5\sigma$ level at the HE-LHC with the integrated luminosity $\mathcal{L}=15{\text{ab}}^{-1}$. We also present the $2\sigma$ exclusion limits of the stop mass at the HL-LHC and HE-LHC.

    hep-phNPB(2020)·3 citations
15. 15*

    Generalised $\mu$-$\tau$ symmetries and calculable gauge kinetic and mass mixing in $U(1{)}_{L_{\mu }-L_{\tau }}$ models

    Anjan S. Joshipura🇮🇳 · Namit Mahajan🇮🇳 · Ketan M. Patel🇮🇳

    Extensions of the standard model with a $U(1)$ gauge symmetry contain gauge invariant kinetic mixing, $\sin \chi$, and gauge non-invariant mass mixing, $\delta M^2$, between the hypercharge and the new gauge boson $Z^{\prime }$. These represent a priori incalculable but phenomenologically important parameters of the theory. They become calculable if there exist spontaneously or softly broken symmetries which forbid them at tree level but allow their generation at the loop level. We discuss various symmetries falling in this category in the context of the gauged $L_{\mu }-L_{\tau }$ models and their interplay with lepton mixing. It is shown that one gets phenomenologically inconsistent lepton mixing parameters if these symmetries are exact. Spontaneous breaking of these symmetries can lead to consistent lepton mixing and also generates finite and calculable values of these parameters at one or two loop order depending on the underlying symmetry. We calculate these parameters in two specific cases: (i) the standard seesaw model with $\mu$-$\tau$ symmetry broken by the masses of the right-handed neutrinos and (ii) in a model containing a pair of vectorlike charged leptons which break $\mu$-$\tau$ symmetry. In case (i), the right-handed neutrinos are the only source of gauge mixing. The kinetic mixing parameters are suppressed and vanish if the right-handed neutrinos decouple from the theory. In contrast, there exists a finite gauge mixing in case (ii) which survives even when the masses of vectorlike leptons are taken to infinity, exhibiting non-decoupling behaviour. The seesaw model discussed here represents a complete framework with practically no kinetic mixing and hence can survive a large number of experimental probes used to rule out specific ranges in the coupling $g^{\prime }$ and mass $M_{Z^{\prime }}$. The model can generate non-universality in tau decays, which can be tested in future experiments.

    hep-phJHEP(2020)·26 citations
16. 16*

    Initial and final state temperatures of antiproton emission sources in high energy collisions

    Qi Wang🇨🇳 · Fu-Hu Liu🇨🇳

    The momentum or transverse momentum spectra of antiprotons produced at mid-rapidity in proton-helium ($p$+He), gold-gold (Au+Au), deuton-gold ($d$+Au), and lead-lead (Pb+Pb) collisions over an energy range from a few GeV to a few TeV are analyzed by the Erlang distribution, the inverse power-law (the Hagedorn function), and the blast-wave fit, or the superposition of two-component step function. The excitation functions of parameters such as the mean transverse momentum, initial state temperature, kinetic freeze-out temperature, and transverse flow velocity increase (slightly) from a few GeV to a few TeV and from peripheral to central collisions. At high energy and in central collisions, large collision energy is deposited in the system, which results in high degrees of excitation and expansion.

    hep-phhep-exnucl-exnucl-thInt.J.Theor.Phys.(2019)·14 citations
17. 17*

    Hadronic contributions to the muon anomalous moment

    Stefan Groote🇪🇪 · Thomas Mannel🇩🇪 · Alexei A. Pivovarov🇩🇪

    We discuss the hadronic contributions to the muon anomalous magnetic moment. They are dominated by light quark contributions which are constrained by the mechanism of chiral symmetry breaking. Using the leading order result based on $e^{+}{e}^{-}$ scattering data, we show that the next-to-leading order contributions in the fine structure constant $\alpha$ can be reliably calculated. Extending this idea to the hadronic four-point function we give a prediction for the light-by-light contribution.

    hep-phhep-exhep-lat0 citations
18. 18*

    Exact results for scattering on ultra-short plane wave backgrounds

    Anton Ilderton🇬🇧

    We give exact results for the emission spectra of both nonlinear Breit-Wheeler pair production and nonlinear Compton scattering in ultra-intense, ultra-short duration plane wave backgrounds, modelled as delta-function pulses. This includes closed form expressions for total scattering probabilities. We show explicitly that these probabilities do not exhibit the power-law scaling with intensity associated with the conjectured breakdown of (Furry picture) perturbation theory, instead scaling logarithmically in the high-intensity limit.

    hep-phhep-thPRD(2019)·23 citations
19. 19*

    Holographic tetraquarks and the newly observed $T_{cc}^{+}$ at LHCb

    Yizhuang Liu🇨🇳 · Maciej A. Nowak🇵🇱 · Ismail Zahed🇺🇸

    We describe a heavy and exotic tetraquark state as a holographic molecule, by binding the lightest heavy-light meson $(0^{-},1^{-})$ multiplet to a flavored sphaleron, in the bulk of the Witten-Sakai-Sugimoto model. Bound tetraquark states emerge as Efimov states in the heavy quark limit, with a binding energy for charm tetraquark comparable to the $T_{cc}^{+}$ recently reported by the LHCb, but a substantially smaller width, for a large but finite ${}^{\prime }$t Hooft coupling. Fixing the parameters of the model at the empirical mass of $T_{cc}^{+}$ allows us to predict the bindings of the undiscovered so far bottom-charm and bottom tetraquarks, when interpreted as Efimov states.

    hep-phnucl-thPRD(2022)·19 citations
20. 20*

    With or without U(2)? Probing non-standard flavor and helicity structures in semileptonic B decays

    Javier Fuentes-Martín🇨🇭 · Gino Isidori🇨🇭 · Julie Pagès🇨🇭 · Kei Yamamoto🇨🇭

    Motivated by the recent hints of lepton flavor universality violation observed in semileptonic $B$ decays, we analyze how to test flavor and helicity structures of the corresponding amplitudes in view of future data. We show that the general assumption that such non-standard effects are controlled by a $U(2{)}_q\times U(2{)}_{\ell }$ flavor symmetry, minimally broken as in the Standard Model Yukawa sector, leads to stringent predictions on leptonic and semileptonic $B$ decays. Future measurements of $R_{D^{(\ast )}}$, $R_{K^{(\ast )}}$, $\mathcal{B}({\bar{B}}_{c,u}\to \ell \bar{\nu })$, $\mathcal{B}(\bar{B}\to \pi \ell \bar{\nu })$, $\mathcal{B}(B\to \pi \ell \bar{\ell })$, $\mathcal{B}(B_{s,d}\to \ell {\bar{\ell }}^{(\prime )})$, as well as various polarization asymmetries in $\bar{B}\to D^{(\ast )}\tau \bar{\nu }$ decays, will allow to prove or falsify this general hypothesis independently of its dynamical origin.

    hep-phPLB(2020)·83 citations
21. 21*

    Indirect detection imprint of leptophilic dark matter

    Wei Chao🇨🇳 · Zhuyao Wang🇨🇳

    In this paper we revisit constraints on the leptophilic dark matter (DM) arising from the DM indirect detection experiments. Interactions between the charged leptons and the scalar-type, Dirac-type or vector-type DM are written in terms of effective operators. After classifying all interactions that may give non-zero signals in indirect detections, we study constraints on the parameter space of these effective interactions from the latest results of AMS-02, Planck, Fermi-LAT and H.E.S.S., as well as the observed relic abundance. Main results are summarized in the Table. I. It shows that the $\tau$-flavored DM is almost excluded by the DM indirect detection results in some scenario.

    hep-ph1 citation
22. 22*

    Searching for a solar relaxion/scalar with XENON1T and LUX

    Ranny Budnik🇮🇱 · Oz Davidi🇮🇱 · Hyungjin Kim🇮🇱 · Gilad Perez🇮🇱 · Nadav Priel🇮🇱

    We consider liquid xenon dark matter detectors for searching a light scalar particle produced in the solar core, specifically one that couples to electrons. Through its interaction with the electrons, the scalar particle can be produced in the Sun, mainly through Bremsstrahlung process, and subsequently it is absorbed by liquid xenon atoms, leaving prompt scintillation light and ionization events. Using the latest experimental results of XENON1T and Large Underground Xenon, we place bounds on the coupling between electrons and a light scalar as $g_{\varphi ee}<7\times 10^{-15}$ from S1-only analysis, and as $g_{\varphi ee}<2\times 10^{-15}$ from S2-only analysis. These can be interpreted as bounds on the mixing angle with the Higgs, $\sin \theta <2\times 10^{-9}\left(7\times 10^{-10}\right)$, for the case of a relaxion that couples to the electrons via this mixing. The bounds are a factor few weaker than the strongest indirect bound inferred from stellar evolution considerations.

    hep-phPRD(2019)·17 citations
23. 23*

    Middle-atmosphere dynamics observed with a portable muon detector

    Matias Tramontini🇫🇷 · Marina Rosas-Carbajal🇫🇷 · Christophe Nussbaum🇨🇭 · Dominique Gibert🇫🇷 · Jacques Marteau🇫🇷

    In the past years, large particle-physics experiments have shown that muon rate variations detected in underground laboratories are sensitive to regional, middle-atmosphere temperature variations. Potential applications include tracking short-term atmosphere dynamics, such as Sudden Stratospheric Warmings. We report here that such sensitivity is not only limited to large surface detectors under high-opacity conditions. We use a portable muon detector conceived for muon tomography for geophysical applications and we study muon rate variations observed over one year of measurements at the Mont Terri Underground Rock Laboratory, Switzerland (opacity of ~700 meter water equivalent). We observe a direct correlation between middle-atmosphere seasonal temperature variations and muon rate. Muon rate variations are also sensitive to the abnormal atmosphere heating in January-February 2017, associated to a Sudden Stratospheric Warming. Estimates of the effective temperature coefficient for our particular case agree with theoretical models and with those calculated from large neutrino experiments under comparable conditions. Thus, portable muon detectors may be useful to 1) study seasonal and short-term middle atmosphere dynamics, especially in locations where data is lacking such as mid-latitudes; and 2) improve the calibration of the effective temperature coefficient for different opacity conditions. Furthermore, we highlight the importance of assessing the impact of temperature on muon rate variations when considering geophysical applications. Depending on latitude and opacity conditions, this effect may be large enough to hide subsurface density variations due to changes in groundwater content, and should therefore be removed from the time-series.

    ↳ physics.geo-phhep-exhep-phEarth Space Sci.(2019)·11 citations
24. 24*

    Zb tetraquark channel and $B{\bar{B}}^{\ast }$ interaction from lattice QCD

    S. Prelovsek🇸🇮 · H. Bahtiyar🇹🇷 · J. Petkovic🇸🇮

    Two tetraquark candidates $Z_b(10610)$ and $Z_b(10650)$ with flavor structure $\bar{b}b\bar{d}u$ were discovered by Belle experiment in 2011. We present a preliminary $N_f=2$ lattice study of the $\bar{b}b\bar{d}u$ system in the approximation of static $b$ quarks, where the total spin of heavy quarks is fixed to one. The ground and the excited eigen-energies are determined as a function of separation $r$ between $b$ and $\bar{b}$. The lower eigenstates are related to a bottomonium and a pion. One of the higher eigenstates is dominated by $B{\bar{B}}^{\ast }$: its energy is significantly below $m_B+m_{B\ast }$ for r=[0.1,0.4] fm, which suggests sizable attraction. The attractive potential $V(r)$ between $B$ and ${\bar{B}}^{\ast }$ is extracted assuming that this eigenstate is related exclusively to $B{\bar{B}}^{\ast }$. Assuming a certain form of the potential and solving non-relativistic Schrodinger equation, we find a bound state pole below $B{\bar{B}}^{\ast }$ threshold. For certain parametrizations, the bound state is very close to the $B{\bar{B}}^{\ast }$ threshold - this feature could be related to $Z_b(10610)$ in the experiment.

    ↳ hep-lathep-phPoS(2019)·3 citations
25. 25*

    Improvement for Color Glass Condensate factorization: single hadron production in pA collisions at next-to-leading order

    Hao-Yu Liu🇨🇳 · Yan-Qing Ma🇨🇳 · Kuang-Ta Chao🇨🇳

    High order calculation at semi-hard scale is very important, but a satisfactory calculation framework is still missing. We propose a systematic method to regularize rapidity divergences in the CGC factorization, which makes higher order calculation rigorous and straight forward. By applying this method to single hadron production in pA collision, we find the kinematic constraint effect introduced by hand in previous works comes out automatically, but with different values. The difference is crucial for our next-to-leading order (NLO) result to have a smaller theoretical uncertainty comparing with LO result, which makes high order calculation in CGC factorization to be useful. As a byproduct, the negativity problem found in literature can also be overcome in our framework by a proper choosing of factorization scale.

    ↳ nucl-thhep-exhep-phnucl-exPRD(2019)·27 citations
26. 26*

    Quantum tunnelling, real-time dynamics and Picard-Lefschetz thimbles

    Zong-Gang Mou🇳🇴 · Paul M. Saffin🇬🇧 · Anders Tranberg🇳🇴

    We follow up the work, where in light of the Picard-Lefschetz thimble approach, we split up the real-time path integral into two parts: the initial density matrix part which can be represented via an ensemble of initial conditions, and the dynamic part of the path integral which corresponds to the integration over field variables at all later times. This turns the path integral into a two-stage problem where, for each initial condition, there exits one and only one critical point and hence a single thimble in the complex space, whose existence and uniqueness are guaranteed by the characteristics of the initial value problem. In this paper, we test the method for a fully quantum mechanical phenomenon, quantum tunnelling in quantum mechanics. We compare the method to solving the Schrödinger equation numerically, and to the classical-statistical approximation, which emerges naturally in a well-defined limit. We find that the Picard-Lefschetz result matches the expectation from quantum mechanics and that, for this application, the classical-statistical approximation does not.

    ↳ hep-thhep-lathep-phJHEP(2019)·47 citations
27. 27*

    A simple family of solutions of relativistic viscous hydrodynamics for fireballs with Hubble flow and ellipsoidal symmetry

    M. Csanad🇭🇺 · M. I. Nagy🇭🇺 · Z. F. Jiang🇨🇳 · T. Csorgo🇭🇺

    New, analytic solutions of relativistic viscous hydrodynamics are presented, describing expanding fireballs with Hubble-like velocity profile and ellipsoidal symmetry, similar to fireballs created in heavy ion collisions. We find that with these specifications, one obtains solutions where the shear viscosity essentially does not influence the time evolution of the system, thus these solutions are particularly adept tools to study the effect of bulk viscosity alone, which always results in a slower decrease of energy density as well as temperature compared to the case of perfect fluid. We investigate different scenarios for the bulk viscosity and find qualitatively different effects on the time evolution which suggests that there is a possibility to infer the value of bulk viscosity from energy density and temperature measurements in high-energy heavy-ion collisions.

    ↳ nucl-thhep-phGribov-90 Memorial Volume (World Scientif…·6 citations
28. 28*

    Cosmological Polytopes and the Wavefuncton of the Universe for Light States

    Paolo Benincasa🇩🇰

    We extend the investigation of the structure of the late-time wavefunction of the universe to a class of toy models of scalars with time-dependent masses and polynomial couplings, which contains general massive scalars in FRW cosmologies. We associate a universal integrand to each Feynman diagram contributing to the wavefunction of the universe. For certain (light) masses, such an integrand satisfies recursion relations involving differential operators, connecting states with different masses and having, as a seed, the massless scalar (which describes a conformally coupled scalar as a special case). We show that it is a degenerate limit of the canonical form of a generalisation of the cosmological polytopes describing the wavefunction for massless scalars. Intriguingly, the flat-space scattering amplitude appears as a higher codimension face: it is encoding the leading term in the Laurent expansion as the total energy is taken to zero, with the codimension of the face providing the order of the total energy pole. The same connection between the other faces and the Laurent expansion coefficients holds for the other singularities of the wavefunction of the universe, all of them connectable to flat-space processes. As the degenerate limit is taken, some of the singularities of the canonical form of the polytope collapse onto each other generating higher order poles. Finally, we consider the mass as a perturbative coupling, showing that the contribution to the wavefunction coming from graphs with mass two-point couplings can be identified with a degenerate limit of the canonical form of the cosmological polytope, if the perturbative expansion is done around the conformally coupled state; or as double degenerate limit of the canonical form of the extension of the cosmological polytopes introduced in the present paper, if the perturbative expansion is done around minimally coupled states.

    ↳ hep-thgr-qchep-phmath.CO104 citations
29. 29*

    Patterns of flavour symmetry breaking in hadron matrix elements involving u, d and s quarks

    J.M. Bickerton🇦🇺 · R. Horsley🇬🇧 · Y. Nakamura🇯🇵 · H. Perlt🇩🇪 · D. Pleiter🇩🇪 · P.E.L. Rakow🇬🇧 · G. Schierholz🇩🇪 · H. Stüben🇩🇪 · R.D. Young🇦🇺 · J.M. Zanotti🇦🇺

    By considering a flavour expansion about the SU(3)-flavour symmetric point, we investigate how flavour-blindness constrains octet baryon matrix elements after SU(3) is broken by the mass difference between quarks. Similarly to hadron masses we find the expansions to be constrained along a mass trajectory where the singlet quark mass is held constant, which provides invaluable insight into the mechanism of flavour symmetry breaking and proves beneficial for extrapolations to the physical point. Expansions are given up to third order in the expansion parameters. Considering higher orders would give no further constraints on the expansion parameters. The relation of the expansion coefficients to the quark-line-connected and quark-line disconnected terms in the 3-point correlation functions is also given. As we consider Wilson clover-like fermions, the addition of improvement coefficients is also discussed and shown to be included in the formalism developed here. As an example of the method we investigate this numerically via a lattice calculation of the flavour-conserving matrix elements of the vector first class form factors.

    ↳ hep-lathep-phnucl-thPRD(2019)·16 citations
30. 30*

    Brans-Dicke gravity with a cosmological constant smoothes out $\Lambda$CDM tensions

    Joan Sola🇪🇸 · Adria Gomez-Valent🇩🇪 · Javier de Cruz Perez🇺🇸 · Cristian Moreno-Pulido🇪🇸

    We analyze Brans-Dicke gravity with a cosmological constant, $\Lambda$, and cold dark matter (BD-$\Lambda$CDM for short) in the light of the latest cosmological observations on distant supernovae, Hubble rate measurements at different redshifts, baryonic acoustic oscillations, large scale structure formation data, gravitational weak-lensing and the cosmic microwave background under full Planck 2015 CMB likelihood. Our analysis includes both the background and perturbations equations. We find that BD-$\Lambda$CDM is observationally favored as compared to the concordance $\Lambda$CDM model, which is traditionally defined within General Relativity (GR). In particular, some well-known persisting tensions of the $\Lambda$CDM with the data, such as the excess in the mass fluctuation amplitude ${\sigma }_8$ and specially the acute $H_0$-tension with the local measurements, essentially disappear in this context. Furthermore, viewed from the GR standpoint, BD-$\Lambda$CDM cosmology mimics quintessence at $\gtrsim 3\sigma$ c.l. near our time.

    ↳ astro-ph.COgr-qchep-phApJL(2019)·152 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.