Tue·Oct 9, 2018Tuesday·October 9, 2018

1. 01*

   Optimized determination of the polarized Bjorken sum rule in pQCD

   D. Kotlorz🇵🇱 · S. V. Mikhailov🇷🇺

   We present the method of numerical optimization for the perturbative series using the renormalization group in quantum chromodynamics. We apply our approach to the perturbation series in ${\alpha }_s$ for the coefficient function $C_{\text{Bjp}}({\alpha }_s)$ of the Bjorken sum rule for the polarized deep inelastic lepton-hadron scattering. We optimize the Bjorken sum rule value, ${\Gamma }_1^{\text{p-n}}$, at the COMPASS, SLAC and JLab kinematics and compare the obtained results with the experimental measurements and also with the truncated Bjorken sum rule predictions.

   hep-phPRD(2019)·16 citations
2. 02*

   Low energy kaon-hyperon interaction

   Marcelo G. L. Nogueira Santos🇪🇸 · Celso C. Barros Jr🇧🇷

   In this work we study the low energy kaon-hyperon interaction considering effective chiral Lagrangians that include kaons, $\sigma$ mesons, hyperons and the corresponding resonances. We calculate the scattering amplitudes, and then the total cross sections, angular distributions, polarizations and the $S$ and $P$ phase shifts.

   hep-phPRC(2019)·7 citations
3. 03*

   Probing Axial-Vector Charmonia ${\chi }_{c1}(1P)$ and ${\chi }_{c1}(2P)$

   J.Y. Süngü🇹🇷 · A.C. Jumasahatov🇹🇷

   We investigate the ground-state heavy quarkonium ${\chi }_{c1}(1P)$ and its first excited state ${\chi }_{c1}(2P)$ with quantum numbers $J^{PC}=1^{++}$. The masses and decay constants of these charmonium states are computed using two-point QCD sum rule method by including quark, gluon and mixed condensates up to dimension-8. We compare our numerical results with the available experimental data as well as existing theoretical predictions in the literature.

   hep-phJ.Phys.G(2019)·4 citations
4. 04*

   Thermally modified sterile neutrino portal dark matter and gravitational waves from phase transition: The Freeze-in case

   Ligong Bian🇨🇳 · Yi-Lei Tang🇰🇷

   We consider the thermal effects into the evaluation of the dark matter production process. With the assistance of the right handed neutrinos, the freeze-in massive particle dark matter production history can be modified by the two-step phase transitions. The kinematic of decay/inverse decay or annihilation processes can be affected by the finite temperature effects as the Universe cools down. The history of the symmetry respected by the model can be revealed by the DM relic abundance evolution processes. The strong first order electroweak phase transition generated gravitational waves can be probed. The number of extra scalars for the Hierarchy problem can be probed through the Higgs off-shell searches at the LHC.

   hep-phastro-ph.COJHEP(2018)·74 citations
5. 05*

   The study of light invisible particles in $B_c$ decays

   Geng Li🇨🇳 · Tianhong Wang🇨🇳 · Yue Jiang🇨🇳 · Xiao-Ze Tan🇨🇳 · Guo-Li Wang🇨🇳

   In this paper, we study the light scalar and pseudoscalar invisible particles in the flavor changing neutral current processes of the $B_c$ meson. Effective operators are introduced to describe the couplings between quarks and light invisible particles. The Wilson coefficients are extracted from the experimental results of the $B$ and $D$ mesons, which are used to predict the upper limits of the branching fractions of the similar decay processes for the $B_c$ meson. The hadronic transition matrix element is calculated with the instantaneously approximated Bethe-Salpeter method. The upper limits of the branching fractions when $m_{\chi }$ taking different values are presented. It is found that at some region of $m_{\chi }$, the channel $B_c\to D_s^{(\ast )}\chi \chi$ has the largest upper limit which is of the order of $10^{-6}$, and for $B_c\to D_s^{\ast }\chi {\chi }^{†}$, the largest value of the upper limits can achieve the order of $10^{-5}$. Other decay modes, such as $B_c\to D^{(\ast )}\chi {\chi }^{(†)}$ and $B_c\to B^{(\ast )}\chi {\chi }^{(†)}$, are also considered.

   hep-phJHEP(2019)·9 citations
6. 06*

   Quadrupole moments of spin-1 systems: the rho meson, the S-wave deuteron and some general constraints

   A.F. Krutov🇷🇺 · V.E. Troitsky🇷🇺

   We costruct the relativistic operator of the quadrupole moment of two-particle composite spin one systems with zero orbital moment of the relative motion and derive explicit analytical expression for the quadrupole moment using the approach to relativistic composite systems based on our version of the instant-form relativistic quantum mechanics (RQM). We calculate the quadrupole moments of the rho meson and of the S-wave deuteron without any free parameters, using our unified pi&rho model (Phys. Rev.D 93, 036007 (2016); 97, 033007 (2018)) and our previous results on deuteron. Our calculation gives Q_rho=-0.158+-0.04 GeV^-2 and Q_d=-1.4*10^-4 GeV^-2. Having in our disposition the rather general form of the quadrupole-moment operator we for the first time formulate the problem of the upper and lower bounds for possible values of the quadrupole moment of a two-particle system with indicated quantum numbers for a large range of constituent masses, and partially solve it.

   hep-phnucl-thPRD(2019)·2 citations
7. 07*

   Hadronic Molecular States Composed of Spin-$\frac{3}{2}$ Singly Charmed Baryons

   Bin Yang🇨🇳 · Lu Meng🇨🇳 · Shi-Lin Zhu🇨🇳

   We investigate the possible deuteron-like molecules composed of a pair of charmed spin-$\frac{3}{2}$ baryons, or one charmed baryon and one charmed antibaryon within the one-boson-exchange (OBE) model. For the spin singlet and triplet systems, we consider the couple channel effect between systems with different orbital angular momentum. Most of the systems have binding solutions. The couple channel effect plays a significant role in the formation of some loosely bound states. The possible molecular states of ${\Omega }_c^{\ast }{\Omega }_c^{\ast }$ and ${\Omega }_c^{\ast }{\bar{\Omega }}_c^{\ast }$ might be stable once produced.

   hep-phhep-exhep-latnucl-thEPJA(2019)·12 citations
8. 08*

   Relativistic description of the ${\Xi }_b$ baryon semileptonic decays

   R. N. Faustov🇷🇺 · V. O. Galkin🇷🇺

   Semileptonic decays of the ${\Xi }_b$ baryon are studied in the framework of the relativistic quark-diquark model based on the quasipotential approach. The weak decay form factors are calculated with the comprehensive account of all relativistic effects without employing nonrelativistic and heavy quark expansions. On this basis differential and total decay rates as well as different asymmetry parameters are calculated for the heavy-to-heavy ${\Xi }_b\to {\Xi }_c\ell {\nu }_{\ell }$ and heavy-to-light ${\Xi }_b\to \Lambda \ell {\nu }_{\ell }$ semileptonic decays. Predictions for the ratios of such decays involving $\tau$ lepton and muon are presented.

   hep-phhep-exPRD(2018)·28 citations
9. 09*

   Does the bottomonium counterpart of $X(3872)$ exist?

   Zhi-Yong Zhou🇨🇳 · Dian-Yong Chen🇨🇳 · Zhiguang Xiao🇨🇳

   A narrow line shape peak at about 10615 MeV, just above the threshold in the $B{\bar{B}}^{\ast }$ channel, which can be regarded as the signal of bottomonium counterpart of $X(3872)$, $X_b$, is predicted by using the extended Friedrichs scheme. Though a virtual state is found at about 10593 MeV in this scheme, we point out that the peak is contributed mainly by the coupling form factor, which comes from the convolution of the interaction term and meson wave functions including the one from ${\chi }_{b1}(4P)$, but not mainly by the virtual-state pole. In this picture, the reason why $X_b$ signal is not observed in the ${\rm Y}{\pi }^{+}{\pi }^{-}$ and ${\rm Y}{\pi }^{+}{\pi }^{-}{\pi }^0$ channels can also be understood. The ${\chi }_{b1}(4P)$ mass and width are found to be about 10771 MeV and 6 MeV, respectively and a dynamically generated broad resonance is also found with its mass and width at about 10672 MeV and 78 MeV, respectively. The line shapes of these two states are also affected by the form factor effect. Thus, this study also emphasizes the importance of the structure of the wave functions of high radial excitations in the analysis of the line shapes, and provides a caveat that some signals may be generated from the structures of the form factors rather than from poles.

   hep-phhep-exnucl-thPRD(2019)·10 citations
10. 10*

    Can the $\psi (4040)$ explain the peak associated with $Y(4008)$?

    Milena Piotrowska🇵🇱 · Francesco Giacosa🇵🇱 · Peter Kovacs🇭🇺

    We study the well-known resonance $\psi (4040)$, corresponding to a $3^3{S}_1$ charm-anticharm vector state $\psi (3S)$, within a QFT approach, in which the decay channels into $DD$, $D^{\ast }D$, $D^{\ast }{D}^{\ast }$, $D_s{D}_s$ and $D_s^{\ast }{D}_s$ are considered. The spectral function shows sizable deviations from a Breit-Wigner shape (an enhancement, mostly generated by $D{D}^{\ast }$ loops, occurs); moreover, besides the $c\bar{c}$ pole of $\psi (4040)$, a second dynamically generated broad pole at $4$ GeV emerges. Naively, it is tempting to identify this new pole with the unconfirmed state $Y(4008).$ Yet, this state was not seen in the reaction $e^{+}{e}^{-}\to \psi (4040)\to D{D}^{\ast }$, but in processes with ${\pi }^{+}{\pi }^{-}J/\psi$ in the final state. A detailed study shows a related but different mechanism: a broad peak at $4$ GeV in the process $e^{+}{e}^{-}\to \psi (4040)\to D{D}^{\ast }\to {\pi }^{+}{\pi }^{-}J/\psi$ appears when $D{D}^{\ast }$ loops are considered. Its existence in this reaction is not necessarily connected to the existence of a dynamically generated pole, but the underlying mechanism - the strong coupling of $c\bar{c}$ to \ $D{D}^{\ast }$ loops - can generate both of them. Thus, the controversial state $Y(4008)$ may not be a genuine resonance, but a peak generated by the $\psi (4040)$ and $D^{\ast }D$ loops with ${\pi }^{+}{\pi }^{-}J/\psi$ in the final state.

    hep-phEPJC(2019)·15 citations
11. 11*

    QCD critical end point from a realistic PNJL model

    Kun Xu🇨🇳 · Zhibin Li🇨🇳 · Mei Huang🇨🇳

    With parameters fixed by critical temperature and equation of state at zero baryon chemical potential, a realistic Polyakov--Nambu--Jona-Lasinio (rPNJL) model predicts a critical end point of chiral phase transition at $({\mu }_B^E=720\mathrm{MeV},T^E=93\mathrm{MeV})$. The extracted freeze-out line from heavy ion collisions is close to the chiral phase transition boundary in the rPNJL model, and the kurtosis $\kappa {\sigma }^2$ of baryon number fluctuations from the rPNJL model along the experimental freeze-out line agrees well with the BES-I measurement. Our analysis shows that the dip structure of measured $\kappa {\sigma }^2$ is determined by the relationship between the freeze-out line and chiral phase transition line at low baryon density region, and the peak structure can be regarded as a clean signature for the existence of CEP.

    hep-phhep-latnucl-thEPJ Web Conf.(2018)·5 citations
12. 12*

    The $Y(4260)$ and $Y(4360)$ enhancements within coupled-channels

    Susana Coito🇵🇱

    Puzzling structures have been observed in the charmonium energy region, namely the $Y(4260)$ and the $Y(4360)$, that cannot be easily accommodated within quark model frameworks. The proximity of nearby dominant hadronic thresholds suggests that they play an important role in the formation of the enhancements. We present results of an unitarized effective Lagrangian model, where mesonic loops, equivalent to coupled-channels, and charmonium vectors $\psi$ interplay to generate line-shapes and poles.

    hep-phEPJ Web Conf.(2019)·2 citations
13. 13*

    Testing Lorentz invariance and CPT symmetry using gamma-ray burst neutrinos

    Xinyi Zhang🇨🇳 · Bo-Qiang Ma🇨🇳

    A recent work [Y. Huang and B.-Q. Ma, Commun. Phys. {\bf 1}, 62 (2018)] associated all four PeV neutrinos observed by IceCube to gamma-ray bursts (GRBs), and revealed a regularity which indicates a Lorentz violation scale $E_{\mathrm{LV}}=(6.5\pm 0.4)\times 10^{17}$ GeV with opposite sign factors $s=\pm 1$ between neutrinos and antineutrinos. The association of "time delay" and "time advance" events with neutrinos and antineutrinos (or vice versa) is only a hypothesis since the IceCube detector cannot tell the chirality of the neutrinos, and further experimental tests are needed to verify this hypothesis. We derive the values of the CPT-odd Lorentz violating parameters in the standard-model extension (SME) framework, and perform a threshold analysis on the electron-positron pair emission of the superluminal neutrinos (or antineutrinos). We find that different neutrino/antineutrino propagation properties, suggested by Y. Huang and B.-Q. Ma, can be described in the SME framework with both Lorentz invariance and CPT symmetry violation, but with a threshold energy constraint. A viable way on testing the CPT symmetry violation between neutrinos and antineutrinos is suggested.

    hep-phPRD(2019)·23 citations
14. 14*

    R-parity Violation and Light Neutralinos at CODEX-b, FASER, and MATHUSLA

    Daniel Dercks🇩🇪 · Jordy de Vries🇺🇸 · Herbi K. Dreiner🇩🇪 · Zeren Simon Wang🇩🇪

    The $LQ\bar{D}$ operator in R-parity-violating supersymmetry can lead to meson decays to light neutralinos and neutralino decays to lighter mesons, with a long lifetime. Since the high-luminosity LHC is expected to accumulate as much as 3/ab of data, several detectors proposed to be built at the LHC may probe unexplored regions in the parameter space, for long-lived neutralinos. We estimate the sensitivity of the recently proposed detectors, CODEX-b, FASER, and MATHUSLA, for detecting such light neutralinos singly produced from $D$- and $B$-meson decays in a list of benchmark scenarios, and discuss the advantages and disadvantages of the proposed detectors in this context. We also present our results in a model independent fashion, which can be applied to any long-lived particle with mass in the GeV regime.

    hep-phPRD(2019)·76 citations
15. 15*

    Producing a new Fermion in Coherent Elastic Neutrino-Nucleus Scattering: from Neutrino Mass to Dark Matter

    Vedran Brdar🇩🇪 · Werner Rodejohann🇩🇪 · Xun-Jie Xu🇩🇪

    We consider the production of a new MeV-scale fermion in coherent elastic neutrino-nucleus scattering. The effect on the measurable nucleon recoil spectrum is calculated. Assuming that the new fermion couples to neutrinos and quarks via a singlet scalar, we set limits on its mass and coupling using COHERENT data and also determine the sensitivity of the CONUS experiment. We investigate the possible connection of the new fermion to neutrino mass generation. The possibility of the new fermion being the dark matter particle is also studied.

    hep-phastro-ph.COhep-exJHEP(2018)·77 citations
16. 16*

    Color-octet scalar decays to a gluon and an electroweak gauge boson in the Manohar-Wise model

    Alper Hayreter🇹🇷 · German Valencia🇦🇺

    We present one loop results for the amplitudes giving rise to couplings between a color octet scalar, a gluon, and an electroweak gauge boson. These amplitudes could signal new physics in $\gamma$ jet, $Z$ jet and $W$ jet production at the LHC. We compute the relevant branching ratios and identify regions of parameter space where these decay modes become important. This can happen for scalar masses below the threshold for decay into heavy quark pairs ($t\bar{t}$ and $t\bar{b}$); or for small Yukawa couplings in which case the colored scalars are fermiophobic. In the case of light scalars, $\mathcal{B}(S\to \gamma g)$ can reach up to 10\% whereas $\mathcal{B}(S\to Zg)$ can reach a few percent. In the fermiophobic region of parameter space, $\mathcal{B}(S\to \gamma g)$ and $\mathcal{B}(S\to Zg)$ can reach up to 72\% and 28\% respectively, whereas $\mathcal{B}(S\to gg)$ can be 100\%. For the charged scalar, the decay mode $\mathcal{B}(S^{\pm }\to W^{\pm }g)$ can become dominant in both scenarios.

    hep-phPRD(2020)·12 citations
17. 17*

    Line intensity mapping with [CII] and CO(1-0) as probes of primordial non-Gaussianity

    Azadeh Moradinezhad Dizgah🇺🇸 · Garrett K. Keating🇺🇸

    Constraints on primordial non-Gaussianity (PNG) will shed light on the origin of primordial fluctuations and the physics of the early universe. The intensity mapping technique is a promising probe of structure formation on large scales; at high redshifts, it can provide complementary information to other cosmological probes. We explore the potential of future wide-field [CII] and CO intensity mapping surveys in constraining PNG of the local shape, which induces a distinct, scale-dependent correction to the line bias. We explore the parameter space of CO and [CII] survey designs that can achieve the nominal target of $\sigma (f_{\mathrm{NL}}^{\mathrm{loc}})=1$ and further calculate what constraints such surveys can place on PNG of the equilateral, orthogonal, and quasi-single field shapes. We further test the dependence of these constraints on various model assumptions; namely the halo mass function, modeling of line bias, and correlation between mass and [CII]/CO luminosity. We find that the ability of CO and [CII] intensity mapping surveys to constrain $f_{\mathrm{NL}}^{\mathrm{loc}}$ relies heavily on the spectral (redshift) coverage, requiring at least a coverage of an octave in frequency, to produce significant results, with the optimized surveys generally covering between $z\sim [2-8]$. As this redshift window partially overlaps with 21-cm EoR experiments like the Hydrogen Epoch of Reionization Array (HERA), we additionally explore the prospects for a hypothetical set of surveys to place constraints on $\sigma (f_{\mathrm{NL}}^{\mathrm{loc}})$ utilizing multi-tracer analysis between the lines of HI, CO, and [CII].

    ↳ astro-ph.COhep-phhep-thApJ(2019)·76 citations
18. 18*

    On Mass correction to Chiral Vortical Effect and Chiral Separation Effect

    Shu Lin🇨🇳 · Lixin Yang🇨🇳

    We study coefficients of axial chiral vortical effect and chiral separation effect at finite temperature and vector chemical potential in massive theories. We present two independent methods of calculating the coefficients: one from field theory and the other using the mass term in axial anomaly equation. An ambiguity in the integration constant similar to hydrodynamic approach to axial chiral vortical effect exists in the latter, but can be fixed naturally in the presence of mass. We obtain perfect agreement between the methods. The results of axial chiral vortical effect and chiral separation effect indicate that the presence of mass generically suppresses the two coefficients, with less suppression at larger chemical potential. For phenomenologically relevant case of quark gluon plasma with three quark flavor, we find the correction is negligible.

    ↳ nucl-thhep-phhep-thPRD(2018)·45 citations
19. 19*

    Supporting High-Performance and High-Throughput Computing for Experimental Science

    E. A. Huerta🇺🇸 · Roland Haas🇺🇸 · Shantenu Jha🇺🇸 · Mark Neubauer🇺🇸 · Daniel S. Katz🇺🇸

    The advent of experimental science facilities-instruments and observatories, such as the Large Hadron Collider, the Laser Interferometer Gravitational Wave Observatory, and the upcoming Large Synoptic Survey Telescope-has brought about challenging, large-scale computational and data processing requirements. Traditionally, the computing infrastructure to support these facility's requirements were organized into separate infrastructure that supported their high-throughput needs and those that supported their high-performance computing needs. We argue that to enable and accelerate scientific discovery at the scale and sophistication that is now needed, this separation between high-performance computing and high-throughput computing must be bridged and an integrated, unified infrastructure provided. In this paper, we discuss several case studies where such infrastructure has been implemented. These case studies span different science domains, software systems, and application requirements as well as levels of sustainability. A further aim of this paper is to provide a basis to determine the common characteristics and requirements of such infrastructure, as well as to begin a discussion of how best to support the computing requirements of existing and future experimental science facilities.

    ↳ cs.DCastro-ph.HEgr-qchep-ex+2Comput.Softw.Big Sci.(2019)·9 citations
20. 20*

    MOND in galaxy groups

    Mordehai Milgrom🇮🇱

    Galaxy groups, which have hardly been looked at in MOND, afford probing the acceleration discrepancies in regions of system-parameter space that are not accessible in well-studied galactic systems, such as galaxies, galaxy clusters, and dwarf-spheroidal satellites of galaxies. Groups are typically the size of galaxy-cluster cores, but have masses typically only a few times that of a single galaxy. Accelerations in groups get far below those in galaxies, and far below the MOND acceleration. So much so, that many groups might be affected by the external-field effect, which is unique to MOND, due to background accelerations. Here, I analyze the MOND dynamics of 53 galaxy groups, recently catalogued in 3 lists. Their Newtonian, K-band, dynamical $M/L$ ratios are a few tens to several hundreds solar units, with $⟨M_d/L_K⟩=(56,25,30)M_{\odot }/L_{\odot }$, respectively for the 3 lists; thus evincing very large acceleration discrepancies. I find here that MOND requires dynamical $M_M/L_K$ values of order $1M_{\odot }/L_{\odot }$, with $⟨M_M/L_K⟩=(0.8,0.56,1.0)M_{\odot }/L_{\odot }$, for the 3 lists, which are in good agreement with population-synthesis stellar values, and with those found in individual galaxies. MOND thus accounts for the observed dynamics in those groups with baryons alone, and no need for dark matter -- an important extension of MOND analysis from galaxies to galactic systems, which, to boot, have characteristic sizes of several hundred kiloparsecs, and accelerations much lower than probed before -- only a few percent of MOND's $a_0$. The acceleration discrepancies evinced by these groups thus conform to the deep-MOND prediction: $g\approx (g_N{a}_0{)}^{1/2}$, down to these very low accelerations ($g$ is the measured, and $g_N$ the baryonic, Newtonian acceleration).

    ↳ astro-ph.GAgr-qchep-phPRD(2018)·13 citations
21. 21*

    Spectral Representation of Thermal OTO Correlators

    Soumyadeep Chaudhuri🇮🇳 · Chandramouli Chowdhury🇮🇳 · R. Loganayagam🇮🇳

    We study the spectral representation of finite temperature, out of time ordered (OTO) correlators on the multi-time-fold generalised Schwinger-Keldysh contour. We write the contour-ordered correlators as a sum over time-order permutations acting on a funda- mental array of Wightman correlators. We decompose this Wightman array in a basis of column vectors, which provide a natural generalisation of the familiar retarded-advanced basis in the finite temperature Schwinger-Keldysh formalism. The coefficients of this de- composition take the form of generalised spectral functions, which are Fourier transforms of nested and double commutators. Our construction extends a variety of classical results on spectral functions in the SK formalism at finite temperature to the OTO case.

    ↳ hep-thcond-mat.stat-mechhep-phnucl-thJHEP(2019)·39 citations
22. 22*

    Secondary cosmic-ray nucleus spectra disfavor particle transport in the Galaxy without reacceleration

    Qiang Yuan🇨🇳 · Cheng-Rui Zhu🇨🇳 · Xiao-Jun Bi🇨🇳 · Da-Ming Wei🇨🇳

    The precise observations of Galactic cosmic ray fluxes of the secondary family, such as Li, Be, B, are expected to have significant implications on our understanding of the cosmic ray origin and propagation. Here we employ the recent very precise measurements of those species by the Alpha Magnetic Spectrometer on the International Space Station, together with their parent species (C and O), as well as the data collected by the Voyager-1 spacecraft outside the heliosphere and the Advanced Composition Explorer, to investigate the propagation of cosmic rays in the Milky Way. We consider the diffusion of cosmic rays plus reacceleration or convection effect during the propagation, and find that the reacceleration model can fit the data significantly better than the convection model. We further find that for the reacceleration model, the spectral hardenings of both the primary and secondary particles can be well described by the injection hardening without including additional propagation hardening. This is due to that the reacceleration effect results in a steeper secondary-to-primary ratio at low energies, and can thus naturally reproduce the fact that the secondary spectra harden more than the primary spectra found by AMS-02.

    ↳ astro-ph.HEhep-phJCAP(2020)·36 citations
23. 23*

    On the Possible Enhancement of the Global $21$-cm Signal at Reionization from the Decay of Cosmic String Cusps

    Robert Brandenberger🇨🇦 · Bryce Cyr🇨🇦 · Timothée Schaeffer🇫🇷

    We consider cosmic string cusp annihilations as a possible source of enhancement to the global background radiation temperature in $21$-cm photons at reionization. A soft photon spectrum is induced via the Bremsstrahlung and Synchrotron emission of electrons borne out of QCD jets formed off the cusp. The maximal energy density background comes from synchrotron induced photons with a string tension of $G\mu \sim 10^{-18}$. In this instance, the radiation background at reionization is heated up by $5\cdot 10^{-3}K$. We find that the depth of the absorption trough ($\delta T_b$) in $21$-cm at reionization is altered by one part in $10^4$ from the strings, requiring high precision measurements to be detectable. This mechanism cannot explain the $\delta T_b$ observed by the EDGES experiment.

    ↳ astro-ph.COgr-qchep-phhep-thJCAP(2019)·13 citations
24. 24*

    Parkes Pulsar Timing Array constraints on ultralight scalar-field dark matter

    Nataliya K. Porayko🇩🇪 · Xingjiang Zhu🇦🇺 · Yuri Levin🇺🇸 · Lam Hui🇺🇸 · George Hobbs🇦🇺 · Aleksandra Grudskaya🇷🇺 · Konstantin Postnov🇷🇺 · Matthew Bailes🇦🇺 · N. D. Ramesh Bhat🇦🇺 · William Coles🇺🇸 · Shi Dai🇦🇺 · James Dempsey🇦🇺 and 18 other authors

    It is widely accepted that dark matter contributes about a quarter of the critical mass-energy density in our Universe. The nature of dark matter is currently unknown, with the mass of possible constituents spanning nearly one hundred orders of magnitude. The ultralight scalar field dark matter, consisting of extremely light bosons with $m\sim 10^{-22}$ eV and often called "fuzzy" dark matter, provides intriguing solutions to some challenges at sub-Galactic scales for the standard cold dark matter model. As shown by Khmelnitsky and Rubakov, such a scalar field in the Galaxy would produce an oscillating gravitational potential with nanohertz frequencies, resulting in periodic variations in the times of arrival of radio pulses from pulsars. The Parkes Pulsar Timing Array (PPTA) has been monitoring 20 millisecond pulsars at two to three weeks intervals for more than a decade. In addition to the detection of nanohertz gravitational waves, PPTA offers the opportunity for direct searches for fuzzy dark matter in an astrophysically feasible range of masses. We analyze the latest PPTA data set which includes timing observations for 26 pulsars made between 2004 and 2016. We perform a search in this data set for evidence of ultralight dark matter in the Galaxy using Bayesian and Frequentist methods. No statistically significant detection has been made. We therefore place upper limits on the local dark matter density. Our limits, improving on previous searches by a factor of two to five, constrain the dark matter density of ultralight bosons with $m\le 10^{-23}$ eV to be below $6\text{GeV}{\text{cm}}^{-3}$ with 95\% confidence in the Earth neighborhood. Finally, we discuss the prospect of probing the astrophysically favored mass range $m\gtrsim 10^{-22}$ eV with next-generation pulsar timing facilities.

    ↳ astro-ph.COastro-ph.GAgr-qchep-phPRD(2018)·151 citations
25. 25*

    $N\Omega$ dibaryon from lattice QCD near the physical point

    Takumi Iritani🇯🇵 · Sinya Aoki🇯🇵 · Takumi Doi🇯🇵 · Faisal Etminan🇮🇷 · Shinya Gongyo🇯🇵 · Tetsuo Hatsuda🇯🇵 · Yoichi Ikeda🇯🇵 · Takashi Inoue🇯🇵 · Noriyoshi Ishii🇯🇵 · Takaya Miyamoto🇯🇵 · Kenji Sasaki🇯🇵

    The nucleon($N$)-Omega($\Omega$) system in the S-wave and spin-2 channel (${}^5$S${}_2$) is studied from the (2+1)-flavor lattice QCD with nearly physical quark masses ($m_{\pi }\simeq 146$~MeV and $m_K\simeq 525$~MeV). The time-dependent HAL QCD method is employed to convert the lattice QCD data of the two-baryon correlation function to the baryon-baryon potential and eventually to the scattering observables. The $N\Omega$(${}^5$S${}_2$) potential, obtained under the assumption that its couplings to the D-wave octet-baryon pairs are small, is found to be attractive in all distances and to produce a quasi-bound state near unitarity: In this channel, the scattering length, the effective range and the binding energy from QCD alone read $a_0=5.30(0.44){(}_{-0.01}^{+0.16})$~fm, $r_{\mathrm{eff}}=1.26(0.01){(}_{-0.01}^{+0.02})$~fm, $B=1.54(0.30){(}_{-0.10}^{+0.04})$~MeV, respectively. Including the extra Coulomb attraction, the binding energy of $p{\Omega }^{-}$(${}^5$S${}_2$) becomes $B_{p{\Omega }^{-}}=2.46(0.34){(}_{-0.11}^{+0.04})$~MeV. Such a spin-2 $p{\Omega }^{-}$ state could be searched through two-particle correlations in $p$-$p$, $p$-nucleus and nucleus-nucleus collisions.

    ↳ hep-lathep-exhep-phnucl-ex+1PLB(2019)·157 citations
26. 26*

    Search for anomalous features in gamma-ray blazar spectra corrected for the absorption on the extragalactic background light

    Alexander Korochkin🇷🇺 · Grigory Rubtsov🇷🇺 · Sergey Troitsky🇷🇺

    We consider the ensemble of very-high-energy gamma-ray sources observed at distances and energies where a significant absorption of gamma rays is expected due to pair production on the extragalactic background light (EBL). Previous studies indicated that spectra of these sources, upon correction for the absorption, exhibit unusual spectral hardenings which happen precisely at the energies where the correction becomes significant. Here, we address this subject with the most recent clean sample of distant gamma-ray blazars, making use of published results of imaging atmospheric Cerenkov telescopes and of the Fermi-LAT Pass 8 data, supplemented by the newest absorption models and individual measurements of sources' redshifts. We perform a search for spectral breaks at energies corresponding to unit optical depth with respect to the absorption on EBL. These energies are different for distant and nearby objects, and consequently, such features may not be related to intrinsic properties of the sources. While in some spectra such breaks are not seen, hardenings at distance-dependent energies are present in many of them, though the overall statistical significance of the effect is lower than reported in previous studies. The dependence of the break strength on the redshift found earlier is not confirmed in the new analysis.

    ↳ astro-ph.HEhep-phJCAP(2019)·15 citations
27. 27*

    CP violation in QCD

    Michael Creutz🇺🇸

    Among the parameters of QCD is one that results in CP violation when non-vanishing. This is closely related to possible quark mass terms. It is conventionally interpreted in terms of gauge field topology or alternatively in terms of phases in the quark masses. There is no experimental evidence for this parameter having a non-zero value, a puzzle for theories involving unification.

    ↳ hep-lathep-phPoS(2018)·6 citations
28. 28*

    Classical behaviour of Q-balls in the Wick-Cutkosky model

    A.G. Panin🇷🇺 · M.N. Smolyakov🇷🇺

    In this paper, we continue discussing Q-balls in the Wick--Cutkosky model. Despite Q-balls in this model are composed of two scalar fields, they turn out to be very useful and illustrative for examining various important properties of Q-balls. In particular, in the present paper we study in detail (analytically and numerically) the problem of classical stability of Q-balls, including the nonlinear evolution of classically unstable Q-balls, as well as the behaviour of Q-balls in external fields in the non-relativistic limit.

    ↳ hep-thhep-phEPJC(2019)·13 citations
29. 29*

    Multi-channel Interference in Nonperturbative Multiphoton Pair Production by Gamma Rays Colliding

    Zhaoyang Peng🇨🇳 · Huayu Hu🇨🇳 · Jianmin Yuan🇨🇳

    The electron-positron pair production in the collision of two intense gamma lasers is studied beyond the dipole approximation. The complete electron/positron momentum spectrum obtained by three-dimensional computation shows directly the multi-photon pair production channels and provides a sensitive test on the widely-used concept of the effective mass. Nonperturbative features are identified in the dependence of the total yield on the field intensity. In particular, various breaks in the momentum rings are observed and proved to be a manifestation of particle's energy gaps in the standing light wave induced by the Kapitza-Dirac scattering. A theoretical model of multi-level systems coupled by the Kapitza-Dirac scattering and pair production channels is established. Multi-channel interference effects and pair production suppression are revealed in these systems.

    ↳ cond-mat.mes-hallhep-phPRResearch(2020)·13 citations
30. 30*

    Low-Energy Lepton-Proton Bremsstrahlung via Effective Field Theory

    Pulak Talukdar🇮🇳 · Fred Myhrer🇺🇸 · Ghanashyam Meher🇮🇳 · Udit Raha🇮🇳

    We present a systematic calculation of the cross section for the lepton-proton bremsstrahlung process l + p --> l' + p + gamma in chiral perturbation theory at next-to-leading order. This process corresponds to an undetected background signal for the proposed MUSE experiment at PSI. MUSE is designed to measure elastic scattering of low-energy electrons and muons off a proton target in order to extract a precise value of the proton's r.m.s. radius. We show that the commonly used peaking approximation, which is used to evaluate the radiative tail for the elastic cross section, is not applicable for muon-proton scattering at the low-energy MUSE kinematics. Furthermore, we point out a certain pathology with the standard chiral power counting scheme associated with electron scattering, whereby the next-to-next-to-leading order contribution from the pion loop diagrams is kinematically enhanced and numerically of the same magnitude as the next-to-leading order corrections. We correct a misprint in a commonly cited review article.

    ↳ nucl-thhep-phEPJA(2018)·9 citations
31. 31*

    Dissipative properties of relativistic two-dimensional gases

    A. L. Garcia-Perciante🇲🇽 · A. R. Méndez🇲🇽

    The constitutive equations for the heat flux and the Navier tensor are established for a high temperature dilute gas in two spatial dimensions. The Chapman-Enskog procedure to first order in the gradients is applied in order to obtain the dissipative energy and momentum fluxes from the relativistic Boltzmann equation. The solution for such equation is written in terms of three sets of orthogonal polynomials which are explicitly obtained for this calculation. As in the three dimensional scenario, the heat flux is shown to be driven by the density, or pressure, gradient additionally to the usual temperature gradient given by Fourier's law. For the stress (Navier) tensor one finds, also in accordance with the three dimensional case, a non-vanishing bulk viscosity for the ideal monoatomic relativistic two-dimensional gas. All transport coefficients are calculated analytically for the case of a hard disk gas and the non-relativistic limit for the constitutive equations is verified.

    ↳ cond-mat.stat-mechhep-phphysics.flu-dynPhysica A·3 citations
32. 32*

    The teacher of the gattini (kittens)

    Roberto Casalbuoni🇮🇹 · Daniele Dominici🇮🇹

    The figure of Raoul Gatto, who died in 2017, is remembered here, with an illustration of his career and the main results of his research, along with the personal memories of some of those who worked with him.

    ↳ physics.hist-phhep-phhep-th3 citations
33. 33*

    The wavefunction reconstruction effects in calculation of DM-induced electronic transition in semiconductor targets

    Zheng-Liang Liang🇨🇳 · Lin Zhang🇨🇳 · Ping Zhang🇨🇳 · Fawei Zheng🇨🇳

    The physics of the electronic excitation in semiconductors induced by sub-GeV dark matter (DM) have been extensively discussed in literature, under the framework of the standard plane wave (PW) and pseudopotential calculation scheme. In this paper, we investigate the implication of the all-electron (AE) reconstruction on estimation of the DM-induced electronic transition event rates. As a benchmark study, we first calculate the wavefunctions in silicon and germanium bulk crystals based on both the AE and pseudo (PS) schemes within the projector augmented wave (PAW) framework, and then make comparisons between the calculated excitation event rates obtained from these two approaches. It turns out that in process where large momentum transfer is kinetically allowed, the two calculated event rates can differ by a factor of a few. Such discrepancies are found to stem from the high-momentum components neglected in the PS scheme. It is thus implied that the correction from the AE wavefunction in the core region is necessary for an accurate estimate of the DM-induced transition event rate in semiconductors.

    ↳ cond-mat.mtrl-scihep-phJHEP(2019)·19 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.