Tue·Feb 21, 2017Tuesday·February 21, 2017

1. 01*

   $B_s\to {\mu }^{+}{\mu }^{-}$ as current and future probe of new physics

   Wolfgang Altmannshofer🇺🇸 · Christoph Niehoff🇩🇪 · David M. Straub🇩🇪

   The rare flavour-changing neutral current decay $B_s\to {\mu }^{+}{\mu }^{-}$ is among the most important indirect probes of new physics at the LHC, as it is strongly suppressed in the Standard Model, very sensitive to new physics effects, and theoretically exceptionally clean. We present a thorough state-of-the-art analysis of the constraints on new physics from present and future measurements of this decay, focusing on scalar operators. We show model-independently and in concrete new physics models, namely the MSSM and two leptoquark scenarios, that a future precise measurement of the mass-eigenstate rate asymmetry in $B_s\to {\mu }^{+}{\mu }^{-}$ would allow to disentangle new physics scenarios that would be indistinguishable based on measurements of the branching ratio alone. We also highlight the complementarity between $B_s\to {\mu }^{+}{\mu }^{-}$ and direct searches in both model classes. Our numerics is based on the open source code flavio and is made publicly available.

   hep-phJHEP(2017)·81 citations
2. 02*

   Inclusive Production Through AdS/CFT

   Richard Nally🇺🇸 · Timothy G. Raben🇺🇸 · Chung-I Tan🇺🇸

   It has been shown that AdS/CFT calculations can reproduce certain exclusive 2->2 cross sections in QCD at high energy, both for near-forward and for fixed-angle scattering. In this paper, we extend prior treatments by using AdS/CFT to calculate the inclusive single-particle production cross section in QCD at high center-of-mass energy. We find that conformal invariance in the UV restricts the cross section to have a characteristic power-law falloff in the transverse momentum of the produced particle, with the exponent given by twice the conformal dimension of the produced particle, independent of incoming particle types. We conclude by comparing our findings to recent LHC experimental data from ATLAS and ALICE, and find good agreement.

   hep-phhep-thJHEP(2017)·16 citations
3. 03*

   QCD Axion Star Collapse with the Chiral Potential

   Joshua Eby🇺🇸 · Madelyn Leembruggen🇺🇸 · Peter Suranyi🇺🇸 · L.C.R. Wijewardhana🇺🇸

   In a previous work, we analyzed collapsing axion stars using the low-energy instanton potential, showing that the total energy is always bounded and that collapsing axion stars do not form black holes. In this paper, we provide a proof that the conclusions are unchanged when using instead the more general chiral potential for QCD axions.

   hep-phJHEP(2017)·32 citations
4. 04*

   NRQCD Confronts LHCb Data on Quarkonium Production within Jets

   Reggie Bain🇺🇸 · Lin Dai🇺🇸 · Adam Leibovich🇺🇸 · Yiannis Makris🇺🇸 · Thomas Mehen🇺🇸

   We analyze the recent LHCb measurement of the distribution of the fraction of the transverse momentum, $z(J/\psi )$, carried by the $J/\psi$ within a jet. LHCb data is compared to analytic calculations using the fragmenting jet function (FJF) formalism for studying $J/\psi$ in jets. Logarithms in the FJFs are resummed using DGLAP evolution. We also convolve hard QCD partonic cross sections, showered with PYTHIA, with leading order Non Relativistic Quantum Chromodynamics (NRQCD) fragmentation functions and obtain consistent results. Both approaches use Madgraph to calculate the hard process that creates the jet initiating parton. These calculations give reasonable agreement with the $z(J/\psi )$ distribution that was shown to be poorly described by default PYTHIA simulations in the LHCb paper. We compare our predictions for the $J/\psi$ distribution using various extractions of nonperturbative NRQCD long-distance matrix elements (LDMEs) in the literature. NRQCD calculations agree with LHCb data better than default PYTHIA regardless of which fit to the LDMEs is used. LDMEs from fits that focus exclusively on high transverse momentum data from colliders are in good agreement with the LHCb measurement.

   hep-phnucl-thPRL(2017)·85 citations
5. 05*

   Distinguishing between Dirac and Majorana neutrinos in the presence of general interactions

   Werner Rodejohann🇩🇪 · Xun-Jie Xu🇩🇪 · Carlos E. Yaguna🇩🇪

   We revisit the possibility of distinguishing between Dirac and Majorana neutrinos via neutrino-electron elastic scattering in the presence of all possible Lorentz-invariant interactions. Defining proper observables, certain regions of the parameter space can only be reached for Dirac neutrinos, but never for Majorana neutrinos, thus providing an alternative method to differentiate these two possibilities. We first derive analytically and numerically the most general conditions that would allow to distinguish Dirac from Majorana neutrinos, both in the relativistic and non-relativistic cases. Then, we apply these conditions to data on ${\nu }_{\mu }$-$e$ and ${\bar{\nu }}_e$-$e$ scatterings, from the CHARM-II and TEXONO experiments, and find that they are consistent with both types of neutrinos. Finally, we comment on future prospects of this kind of tests.

   hep-phhep-exJHEP(2017)·59 citations
6. 06*

   Charmonium Mass Spectrum with Spin-Dependent Interaction in Momentum-Helicity Space

   M. Radin🇮🇷

   In this paper we have solved the nonrelativistic form of the Lippmann-Schwinger equation in the momentum-helicity space by inserting a spin-dependent quark-antiquark potential model numerically. To this end, we have used the momentum-helicity basis states for describing a nonrelativistic reduction of one gluon exchange potential. Then we have calculated the mass spectrum of the charmonium $\psi (c\bar{c})$, and finally we have compared the results with the another theoretical results and experimental data.

   hep-phAdv.High Energy Phys.(2017)·2 citations
7. 07*

   Energy loss of heavy quarks and $B$ and $D$ meson spectra in PbPb collisions at LHC energies

   Kapil Saraswat🇮🇳 · Prashant Shukla🇮🇳 · Vineet Kumar🇮🇳 · Venktesh Singh🇮🇳

   We study the production and evolution of charm and bottom quarks in hot partonic medium produced in heavy ion collisions. The heavy quarks loose energy in the medium which is reflected in the transverse momentum spectra of heavy mesons. The collisional energy loss of heavy quarks has been calculated using QCD calculations. The radiative energy loss is obtained using two models namely reaction operator formalism and generalized dead cone approach. The nuclear modification factors, $R_{AA}$ as a function of transverse momentum by including shadowing and energy loss are calculated for $D^0$ and $B^{+}$ mesons in PbPb collisions at $\sqrt{s_{NN}}$ = 5.02 TeV and for $D^0$ mesons at $\sqrt{s_{NN}}$ = 2.76 TeV and are compared with the recent measurements. The radiative energy loss from generalized dead cone approach alone is sufficient to produce measured $D^0$ meson $R_{AA}$ at both the LHC energies. The radiative energy loss from reaction operator formalism plus collisional energy loss gives good description of $D^0$ meson $R_{AA}$. For the case of $B^{+}$ meson, the radiative energy loss from generalized dead cone approach plus collisional energy loss gives good description of the CMS data. The radiative process is dominant for charm quarks while for the bottom, both the radiative process and the elastic collisions are important.

   hep-phnucl-thNPA(2017)·16 citations
8. 08*

   Study of isolated prompt photon production in $p$-Pb collisions for the ALICE kinematics

   Muhammad Goharipour🇮🇷 · Hossein Mehraban🇮🇷

   Prompt photon production is known as a powerful tool for testing perturbative QCD predictions and also the validity of parton densities in the nucleon and nuclei especially of the gluon. In this work, we have performed a detailed study on this subject focusing on the isolated prompt photon production in $p$-Pb collisions at forward rapidity at the LHC. The impact of input nuclear modifications obtained from different global analyses by various groups on several quantities has been investigated to estimate the order of magnitude of the difference between their predictions. We have also studied in detail the theoretical uncertainties in the results due to various sources. We found that there is a remarkable difference between the predictions from the nCTEQ15 and other groups in all ranges of photon transverse momentum $p_{\text{T}}^{\gamma }$. Their differences become more explicit in the calculation of the nuclear modification ratio and also the yield asymmetry between the forward and backward rapidities rather than single differential cross sections. We emphasize that future measurements with ALICE will be very useful not only for decreasing the uncertainty of the gluon nuclear modification, but also to accurately determine its central values, especially in the shadowing region.

   hep-phPRD(2017)·17 citations
9. 09*

   Probing Higgs boson couplings in H+$\gamma$ production at the LHC

   Hamzeh Khanpour🇮🇷 · Sara Khatibi🇮🇷 · Mojtaba Mohammadi Najafabadi🇮🇷

   In this paper, we examine the potential of Higgs boson production associated with a photon at the LHC to probe the new physics effects in the framework of the standard model effective field theory. It is shown that the differential kinematic distributions such as photon transverse momentum and invariant mass of Higgs+$\gamma$ in Higgs associated production are powerful variables to explore the coefficients of dimension six operators. The analysis is performed in the decay channel of Higgs boson into a $b\bar{b}$ pair including the main sources of background processes and a realistic simulation of the detector effects. We provide constraints at $95\%$ confidence level on the Wilson coefficients of dimension-six operators affecting Higgs boson plus a photon production. We show to what extent these limits could be improved at the high luminosity LHC. The effect of these constraints on a well-motivated beyond standard model scenario is presented.

   hep-phPLB(2017)·38 citations
10. 10*

    Lattice corrections to the quark quasidistribution at one-loop

    Carl E. Carlson🇺🇸 · Michael Freid (W&M and JLab)🇺🇸

    We calculate radiative corrections to the quark quasidistribution in lattice perturbation theory at one loop to leading orders in the lattice spacing. We also consider one-loop corrections in continuum Euclidean space. We find the infrared behavior of the corrections in Euclidean and Minkowski space are different. We explore features of momentum loop integrals and demonstrate why loop corrections from the lattice perturbation theory and Euclidean continuum do not correspond with their Minkowski brethren, and comment on a recent suggestion for transcending the differences in the results. Further, we examine the role of the lattice spacing $a$ and of the $r$ parameter in the Wilson action in these radiative corrections.

    hep-phhep-latPRD(2017)·52 citations
11. 11*

    The HTL resumed propagators in the light cone gauge

    Qi Chen🇨🇳 · De-fu Hou🇨🇳

    The expression of the HTL resumed gluon propagator in the light cone gauge is derived. In the real time mechanism, using the Mandelstam Leibbrant prescription of $(n\cdot K{)}^{-1}$, we calculate the transverse and longitudinal parts of the gluon HTL self-energy and prove the transverse and longitudinal parts do not have divergence. We also calculate the quark self energy in the HTL approximation, and find it gauge independent. We analytically calculate the damping rates of the hard quark and gluon with this HTL resumed gluon propagator.

    hep-phhep-thCPC(2018)·1 citation
12. 12*

    On the dark radiation problem in the axiverse

    Dmitry Gorbunov🇷🇺 · Anna Tokareva🇷🇺

    String scenarios generically predict that we live in a so called axiverse: the Universe with about a hundred of light axion species which are decoupled from the Standard Model particles. However, the axions can couple to the inflaton which leads to their production after inflation. Then, these axions remain in the expanding Universe contributing to the dark radiation component, which is severely bounded from present cosmological data. We place a general constraint on the axion production rate and apply it to several variants of reasonable inflaton-to-axion couplings. The limit merely constrains the number of ultralight axions and the relative strength of inflaton-to-axion coupling. It is valid in both large and small field inflationary models irrespectively of the axion energy scales and masses. Thus, the limit is complementary to those associated with the Universe overclosure and axion isocurvature fluctuations. In particular, a hundred of axions is forbidden if inflaton universally couples to all the fields at reheating. In the case of gravitational sector being responsible for the reheating of the Universe (which is a natural option in all inflationary models with modified gravity), the axion production can be efficient. We find that in the Starobinsky $R^2$-inflation even a single axion (e.g. the standard QCD-axion) is in tension with the Planck data, making the model inconsistent with the axiverse. The general conclusion is that an inflation with inefficient reheating mechanism and low reheating temperature may be in tension with the presence of light scalars.

    hep-phastro-ph.COhep-thJCAP(2017)·6 citations
13. 13*

    Exploring anomalous $hb\bar{b}$ and $hb\bar{b}\gamma$ couplings in the context of the LHC and an $e^{+}{e}^{-}$ collider

    Siddharth Dwivedi🇮🇳 · Subhadeep Mondal🇮🇳 · Biswarup Mukhopadhyaya🇮🇳

    In the light of the 125 GeV Higgs ($h$) discovery at the Large Hadron Collider (LHC), one of the primary goals of the LHC and possible future colliders is to understand its interactions more precisely. Here we have studied the $h$-$b$-$\bar{b}$-$\gamma$ effective interaction terms arising out of gauge invariant dimension six operators in a model independent setting, as a potential source of new physics. Their role in some detectable final states have been compared with those coming from anomalous $h$-$b$-$\bar{b}$ interactions. We have considered the bounds coming from the existing collider and other low energy experimental data in order to derive constraints on the potential new physics couplings and predict possible collider signals for the two different new physics scenarios in the context of 14 TeV LHC and and a future $e^{+}{e}^{-}$ machine. We conclude that the anomalous $h$-$b$-$\bar{b}$-$\gamma$ coupling can be probed at the LHC at 14 TeV at the 3$\sigma$ level with an integrated luminosity of $\sim 2000{\mathrm{fb}}^{-1}$, which an $e^{+}{e}^{-}$ collider can probe at the 3$\sigma$ level with $\sim 12(7){\mathrm{fb}}^{-1}$ at $\sqrt{s}=250(500)\mathrm{GeV}$. It is also found that anomalous $h$-$b$-$\bar{b}$ interactions, subject to the existing LHC constraints, can not compete with the rates driven by $h$-$b$-$\bar{b}$-$\gamma$ effective interactions.

    hep-phPRD(2017)·2 citations
14. 14*

    Production of heavy Higgs bosons and decay into top quarks at the LHC. II: Top-quark polarization and spin correlation effects

    Werner Bernreuther🇩🇪 · Peter Galler🇩🇪 · Zong-Guo Si🇨🇳 · Peter Uwer🇩🇪

    We analyze, within several parameter scenarios of type-II two-Higgs doublet extensions of the standard model, the impact of heavy neutral Higgs-boson resonances on top-quark pair production and their subsequent decay to dileptonic final states at the LHC (13 TeV). In particular, we investigate the effects of heavy Higgs bosons on top-spin observables, that is, the longitudinal top-quark polarization and top-quark spin correlations. We take into account NLO QCD as well as weak interaction corrections and show that top-spin observables, if evaluated in judiciously chosen top-quark pair invariant mass bins, can significantly enhance the sensitivity to heavy Higgs resonances in top-quark pair events.

    hep-phPRD(2017)·17 citations
15. 15*

    Scanning the Earth with solar neutrinos and DUNE

    Ara Ioannisian🇦🇲 · Alexei Yu. Smirnov🇩🇪 · Daniel Wyler🇨🇭

    We explore oscillations of the solar ${}^8$B neutrinos in the Earth in detail. The relative excess of night ${\nu }_e$ events (the Night-Day asymmetry) is computed as function of the neutrino energy and the nadir angle $\eta$ of its trajectory. The finite energy resolution of the detector causes an important attenuation effect, while the layer-like structure of the Earth density leads to an interesting parametric suppression of the oscillations. Different features of the $\eta -$ dependence encode information about the structure (such as density jumps) of the Earth density profile; thus measuring the $\eta$ distribution allows the scanning of the interior of the Earth. We estimate the sensitivity of the DUNE experiment to such measurements. About 75 neutrino events are expected per day in 40 kt. For high values of $\Delta m_{21}^2$ and $E_{\nu }>$11 MeV, the corresponding D-N asymmetry is about 4\% and can be measured with $15\%$ accuracy after 5 years of data taking. The difference of the D-N asymmetry between high and low values of $\Delta m_{21}^2$ can be measured at the $4\sigma$ level. The relative excess of the ${\nu }_e$ signal varies with the nadir angle up to 50\%. DUNE may establish the existence of the dip in the $\eta -$ distribution at the $(2-3)\sigma$ level.

    hep-phPRD(2017)·25 citations
16. 16*

    Gravitational wave, collider and dark matter signals from a scalar singlet electroweak baryogenesis

    Ankit Beniwal🇦🇺 · Marek Lewicki🇵🇱 · James D. Wells🇺🇸 · Martin White🇦🇺 · Anthony G. Williams🇦🇺

    We analyse a simple extension of the SM with just an additional scalar singlet coupled to the Higgs boson. We discuss the possible probes for electroweak baryogenesis in this model including collider searches, gravitational wave and direct dark matter detection signals. We show that a large portion of the model parameter space exists where the observation of gravitational waves would allow detection while the indirect collider searches would not.

    hep-phastro-ph.COJHEP(2017)·220 citations
17. 17*

    Rotation-driven phase transitions in the cores of pulsars

    R. D. Mellinger🇺🇸 · F. Weber🇺🇸 · W. Spinella🇺🇸 · G. A. Contrera🇦🇷 · M. Orsaria🇦🇷

    In this paper, we discuss the impact of rotation on the particle composition of rotating neutron stars (pulsars). Particular emphasis is put on the formation of quark matter during stellar spin-down, driven by continuous gravitational compression. Our study is based on modern models for the nuclear equation of state whose parameters are tightly constrained by nuclear data, neutron star masses, and the latest estimates of neutron star radii.

    ↳ astro-ph.HEhep-phnucl-thInt.J.Mod.Phys.Conf.Ser.(2017)·0 citations
18. 18*

    MCBooster: a library for fast Monte Carlo generation of phase-space decays on massively parallel platforms

    A. A. Alves Jr🇺🇸 · M. D. Sokoloff🇺🇸

    MCBooster is a header-only, C++11-compliant library that provides routines to generate and perform calculations on large samples of phase space Monte Carlo events. To achieve superior performance, MCBooster is capable to perform most of its calculations in parallel using CUDA- and OpenMP-enabled devices. MCBooster is built on top of the Thrust library and runs on Linux systems. This contribution summarizes the main features of MCBooster. A basic description of the user interface and some examples of applications are provided, along with measurements of performance in a variety of environments

    ↳ hep-exhep-phphysics.comp-phJ.Phys.Conf.Ser.(2017)·2 citations
19. 19*

    Strange hadron production in pp, pPb and PbPb collisions at LHC energies

    Kapil Saraswat🇮🇳 · Prashant Shukla🇮🇳 · Vineet Kumar🇮🇳 · Venktesh Singh🇮🇳

    We present a systematic analysis of transverse momentum $(p_T)$ spectra of the strange hadrons in different multiplicity events produced in pp collision at $\sqrt{s}$ = 7 TeV, pPb collision at $\sqrt{s_{NN}}$ = 5.02 TeV and PbPb collision at $\sqrt{s_{NN}}$ = 2.76 TeV. Both the single and differential freeze out scenarios of strange hadrons $K_s^0$, $\Lambda$ and ${\Xi }^{-}$ are considered while fitting using a Tsallis distribution which is modified to include transverse flow. The $p_T$ distributions of these hadrons in different systems are characterized in terms of the parameters namely, Tsallis temperature $(T)$, power $(n)$ and average transverse flow velocity $(\beta )$. It is found that for all the systems, transverse flow increases as we move from lower to higher multiplicity events. In the case of the differential freeze-out scenario, the degree of thermalization remains similar for events of different multiplicity classes in all the three systems. The Tsallis temperature increases with the mass of the hadrons and also increases with the event multiplicity in pp and pPb system but shows little variation with the multiplicity in PbPb system. In the case of the single freeze-out scenario, the difference between small systems (pp, pPb) and PbPb system becomes more evident. The high multiplicity PbPb events show higher degree of thermalization as compared to the events of pp and pPb systems. The trend of variation of the temperature in PbPb system with event multiplicity is opposite to what is found in the pp and pPb systems.

    ↳ nucl-thhep-phEPJA(2017)·7 citations
20. 20*

    Relaxation of the chiral chemical potential in the dense matter of a neutron star

    Maxim Dvornikov (IZMIRAN, Tomsk State University)🇷🇺

    A model of the generation of a magnetic field in a neutron star is developed, based on an instability of the magnetic field caused by the electroweak interaction between electrons and nucleons in nuclear matter. The rate of change of the helicity of the electrons as they scatter on protons in the dense matter of a neutron star is calculated with the help of methods of quantum field theory. The influence of the electroweak interaction between electrons and background nucleons on the process of change of the helicity is examined. A kinetic equation is derived for the evolution of the chiral chemical potential. The results obtained are used to describe the evolution of the magnetic field in magnetars.

    ↳ astro-ph.HEhep-phRuss.Phys.J.(2017)·6 citations
21. 21*

    Generic Phase Portrait Analysis of the Finite-time Singularities and Generalized Teleparallel Gravity

    W. El Hanafy🇪🇬 · G.G.L. Nashed🇪🇬

    We analyze the common four types of the finite-time singularities using a generic framework of the phase portrait geometric approach. This technique requires that the Friedmann system to be written as a one dimensional autonomous system. We employ a scale factor that has been used widely in literature to realize the four finite-time singularity types, then we show a detailed discussion for each case showing possible novel models. Moreover, we show how different singularity types can play essential roles in different cosmological scenarios. Among several modified gravity theories, we show that the f (T) cosmology is in comfort with the phase portrait analysis, since the field equations include Hubble derivatives only up to first order. Therefore, we reconstruct the f (T) theory which generates these phase portraits. We also perform a complementary analysis using the effective equation of state. Furthermore, we investigate the role of the torsion fluid in realizing the cosmic singularities.

    ↳ gr-qcastro-ph.COhep-phhep-thCPC(2017)·12 citations
22. 22*

    Event-by-Event Simulations of Jet Modification Using the MATTER Event Generator

    Michael Kordell II🇺🇸 · Abhijit Majumder🇺🇸

    The modification of hard jets in the Quark Gluon Plasma (QGP) is studied using the MATTER event generator. Based on the higher twist formalism of energy loss, the MATTER event generator simulates the evolution of highly virtual partons through a medium. These partons sampled from an underlying PYTHIA kernel undergo splitting through a combination of vacuum and medium induced emission. The momentum exchange with the medium is simulated via the jet transport coefficient $\hat{q}$, which is assumed to scale with the entropy density at a given location in the medium. The entropy density is obtained from a relativistic viscous fluid dynamics simulation (VISH2+1D) in 2+1 space time dimensions. Results for jet and hadron observables are presented using an independent fragmentation model. These proceedings will focus on the physics input and simulation details of the MATTER event generator as compared to a variety of test observables.

    ↳ nucl-thhep-ph6 citations
23. 23*

    Decay angular distributions of $K^{\ast }$ and $D^{\ast }$ vector mesons in pion-nucleon scattering

    Sang-Ho Kim🇰🇷 · Yongseok Oh🇰🇷 · Alexander I Titov🇷🇺

    The production mechanisms of open strangeness ($K^{\ast }$) and open charm ($D^{\ast }$) vector mesons in ${\pi }^{-}p$ scattering, namely, ${\pi }^{-}+p\to K^{\ast 0}+\Lambda$ and ${\pi }^{-}+p\to D^{\ast -}+{\Lambda }_c^{+}$, are investigated within the modified quark-gluon string model. In order to identify the major reaction mechanisms, we consider the subsequent decays of the produced vector mesons into two pseudoscalar mesons, i.e., $K^{\ast }\to K+\pi$ and $D^{\ast }\to D+\pi$. We found that the decay distributions and density matrix elements are sensitive to the production mechanisms and can be used to disentangle the vector trajectory and pseudoscalar trajectory exchange models. Our results for $K^{\ast }$ production are compared with the currently available experimental data and the predictions for $D^{\ast }$ production processes are presented as well. Our predictions can be tested at the present or planned experimental facilities.

    ↳ nucl-thhep-phPRC(2017)·9 citations
24. 24*

    Effects of magnetic fields on quark-antiquark interactions

    Claudio Bonati🇮🇹 · Massimo D'Elia🇮🇹 · Marco Mariti🇮🇹 · Michele Mesiti🇮🇹 · Francesco Negro🇮🇹 · Andrea Rucci🇮🇹 · Francesco Sanfilippo🇬🇧

    We discuss some recent results obtained in the study of strong quark-antiquark interactions in the presence of intense external magnetic fields by means of lattice QCD simulations. We confirm previous findings and show that both at zero and finite temperature the external field induces anisotropies in the static quark potential. An in-depth study suggests that the effects are essentially due to the variation of the string tension whose angular dependence can be nicely parametrized by the first allowed term in a Fourier expansion. In the confined phase at high temperature, we observe that the suppression of the string tension is enhanced as the strength of the external field increases. Our results support the idea that the loss of confining properties is the dominant effect related to the decrease of $T_c$ as a function of $B$.

    ↳ hep-lathep-phPoS(2016)·0 citations
25. 25*

    Photoproduction of $\eta$ and ${\eta }^{\prime }$ Mesons on Proton

    V.L. Kashevarov🇩🇪 · L. Tiator🇩🇪 · M. Ostrick (for the A2 Collaboration at MAMI)🇩🇪

    New high-precision total and differential cross sections for $\eta$ and ${\eta }^{\prime }$ photoproduction on the proton obtained by the A2 Collaboration at the Mainz Microtron are presented. The data for $\eta$ photoproduction demonstrate a cusp at the energy W$\sim$1.9~GeV. Furthermore, we present a new version of the $\eta$MAID model for $\eta$ and ${\eta }^{\prime }$ photoproduction. The model includes 23 nucleon resonances parametrized with Breit-Wigner shapes. The background is described by vector and axial-vector meson exchanges in the $t$ channel using the Regge phenomenology. Parameters of the resonances were obtained from a fit to preliminary data of the A2 Collaboration at MAMI and available data from other collaborations. The cusp is explained as a threshold effect due to the opening ${\eta }^{\prime }p$ decay channel of the $N(1895)1/2^{-}$ resonance.

    ↳ nucl-exhep-phnucl-thJPS Conf.Proc.(2017)·10 citations
26. 26*

    Off-shell persistence of composite pions and kaons

    Si-Xue Qin🇺🇸 · Chen Chen🇧🇷 · Cedric Mezrag🇺🇸 · Craig D. Roberts🇺🇸

    In order for a Sullivan-like process to provide reliable access to a meson target as $t$ becomes spacelike, the pole associated with that meson should remain the dominant feature of the quark-antiquark scattering matrix and the wave function describing the related correlation must evolve slowly and smoothly. Using continuum methods for the strong-interaction bound-state problem, we explore and delineate the circumstances under which these conditions are satisfied: for the pion, this requires $-t\lesssim 0.6$GeV${}^2$, whereas $-t\lesssim 0.9$GeV${}^2$ will suffice for the kaon. These results should prove useful in evaluating the potential of numerous experiments at existing and proposed facilities.

    ↳ nucl-thhep-lathep-phnucl-exPRC(2018)·49 citations
27. 27*

    Getting Super-Excited with Modified Dispersion Relations

    Amjad Ashoorioon🇮🇹 · Roberto Casadio🇮🇹 · Ghazal Geshnizjani🇨🇦 · Hyung J. Kim🇨🇦

    We demonstrate that in some regions of parameter space, modified dispersion relations can lead to highly populated excited states, which we dub as "super-excited" states. In order to prepare such super-excited states, we invoke dispersion relations that have negative slope in an interim sub-horizon phase at high momenta. This behaviour of quantum fluctuations can lead to large corrections relative to the Bunch-Davies power spectrum, which mimics highly excited initial conditions. We identify the Bogolyubov coefficients that can yield these power spectra. In the course of this computation, we also point out the shortcomings of the gluing method for evaluating the power spectrum and the Bogolyubov coefficients. As we discuss, there are other regions of parameter space, where the power spectrum does not get modified. Therefore, modified dispersion relations can also lead to so-called "calm excited states" as well. We conclude by commenting on the possibility of obtaining these modified dispersion relations within the Effective Field Theory of Inflation.

    ↳ hep-thastro-ph.COhep-phJCAP(2017)·23 citations
28. 28*

    Positivity Bounds for Scalar Theories

    Claudia de Rham🇬🇧 · Scott Melville🇬🇧 · Andrew J. Tolley🇬🇧 · Shuang-Yong Zhou🇬🇧

    Assuming the existence of a local, analytic, unitary UV completion in a Poincaré invariant scalar field theory with a mass gap, we derive an infinite number of positivity requirements using the known properties of the amplitude at and away from the forward scattering limit. These take the form of bounds on combinations of the pole subtracted scattering amplitude and its derivatives. In turn, these positivity requirements act as constraints on the operator coefficients in the low energy effective theory. For certain theories these constraints can be used to place an upper bound on the mass of the next lightest state that must lie beyond the low energy effective theory if such a UV completion is to ever exist.

    ↳ hep-thastro-ph.COgr-qchep-phPRD(2017)·225 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.