Tue·Mar 21, 2017Tuesday·March 21, 2017

1. 01*

   Profile of multiboson signals

   J.A. Aguilar-Saavedra🇪🇸

   We investigate the visibility of signals characterised by wide bumps over a smoothly falling background that cannot be accurately predicted by Monte Carlo calculations. Examples of such are the wide bumps that triboson and quadriboson resonance cascade decays would yield in diboson resonance searches in fully hadronic final states. We find that the sensitivity to triboson bumps is rather small: signals of a moderate size could be present in current data and yet remain unnoticed. For quadriboson cascade decays the signals can hardly be distinguished from the background in the current searches.

   hep-phhep-exJHEP(2017)·13 citations
2. 02*

   Transverse Momentum Dependent Parton Distributions at Small-x

   Bo-Wen Xiao🇨🇳 · Feng Yuan🇺🇸 · Jian Zhou🇨🇳

   We study the transverse momentum dependent (TMD) parton distributions at small-x in a consistent framework that takes into account the TMD evolution and small-x evolution simultaneously. The small-x evolution effects are included by computing the TMDs at appropriate scales in terms of the dipole scattering amplitudes, which obey the relevant Balitsky-Kovchegov equation. Meanwhile, the TMD evolution is obtained by resumming the Collins-Soper type large logarithms emerged from the calculations in small-x formalism into Sudakov factors.

   hep-phnucl-thNPB(2017)·84 citations
3. 03*

   Constraints and Implications on Higgs FCNC Couplings from Precision Measurement of $B_s\to {\mu }^{+}{\mu }^{-}$ Decay

   Cheng-Wei Chiang🇹🇼 · Xiao-Gang He🇨🇳 · Fang Ye🇹🇼 · Xing-Bo Yuan🇹🇼

   We study constraints and implications of the recent LHCb measurement of $\mathcal{B}(B_s\to {\mu }^{+}{\mu }^{-})$ for tree-level Higgs-mediated flavor-changing neutral current (FCNC) interactions. Combined with experimental data on $B_s$ mass difference $\Delta m_s$, the $h\to \mu \tau$, and the $h\to {\tau }^{+}{\tau }^{-}$ decay branching ratios from the LHC, we find that the Higgs FCNC couplings are severely constrained. The allowed regions for $B_s\to \mu \tau$, $\tau \tau$ and $h\to sb$ decays are obtained. Current data allow large CP violation in the $h\to {\tau }^{+}{\tau }^{-}$ decay. Consequences of the Cheng-Sher ansatz for the Higgs Yukawa couplings are discussed in some detail.

   hep-phPRD(2017)·13 citations
4. 04*

   Resonance a_1(1420) and the Three-Pion Decays of the Tauon

   Peter Lichard🇨🇿

   The role of the a_1(1420) resonance in the three-pion decays of the tau lepton is investigated using a phenomenological model. For all data before 2008, roughly equal fit quality is achieved when the basic a_1(1260) resonance is supplemented with either a_1(1640) or a_1(1420). However, two recent and more precise data sets require resonances with masses that are not very far from that of a_1(1420). This suggests that the axial-vector resonance that accompanies the a_1(1260) in the three-pion decays of the tauon is a_1(1420), not a_1(1640), as believed up to now. More data are needed to demonstrate this definitely.

   hep-phhep-ex1 citation
5. 05*

   More on Electroweak-Skyrmion

   Ryuichiro Kitano🇯🇵 · Masafumi Kurachi🇯🇵

   We discuss the properties of the topological soliton, or the Electroweak-Skyrmion, in the system of the Standard Model Higgs Lagrangian with addition of general O(p^4) terms. We show that the upper bound on the mass of the Electroweak-Skyrmion is about 10 TeV, which is obtained from currently available experimental constraints on coefficients of O(p^4) terms. The impact on the properties of the Electroweak-Skyrmion due to further modification of the Lagrangian is also discussed, and comments on possible mechanisms for the generation of the Electroweak-Skyrmion in the early Universe as a dark matter are given.

   hep-phJHEP(2017)·7 citations
6. 06*

   On the choice of beam polarization in $e^{+}{e}^{-}\to ZZ/Z\gamma$ and anomalous triple gauge-boson couplings

   Rafiqul Rahaman🇮🇳 · Ritesh K. Singh🇮🇳

   The anomalous trilinear gauge couplings of $Z$ and $\gamma$ are studied in $e^{+}{e}^{-}\to ZZ/Z\gamma$ with longitudinal beam polarizations using a complete set of polarization asymmetries for the $Z$ boson. We quantify the goodness of the beam polarization in terms of the likelihood and find the best-choice of $e^{-}$ and $e^{+}$ polarizations to be ($+0.16$, $-0.16$), ($+0.09$, $-0.10$) and ($+0.12$, $-0.12$) for $ZZ$, $Z\gamma$ and combined processes, respectively. Simultaneous limits on anomalous couplings are obtained for these choices of beam polarizations using Markov-Chain--Monte-Carlo (MCMC) for an $e^{+}{e}^{-}$ collider running at $\sqrt{s}=500$ GeV and $\mathcal{L}=100$ fb${}^{-1}$. We find the simultaneous limits for these beam polarizations to be comparable with each other and also comparable with the unpolarized beam case.

   hep-phhep-exEPJC(2017)·36 citations
7. 07*

   Electroweak Baryogenesis and Dark Matter via a Pseudoscalar vs. Scalar

   Parsa Hossein Ghorbani🇮🇷

   We study the electroweak baryogenesis in a fermionic dark matter scenario with a (pseudo)scalar being the mediator in the Higgs portal. It is discussed that the electroweak phase transition turns to be first-order after taking into account the role of the (pseudo)scalar in the thermal effective potential in our extended standard model. Imposing the relic density constraint from the WMAP/Planck and the bounds from the direct detection experiments XENON100/LUX, we show that the dark matter scenario with a scalar mediator is hardly capable of explaining the baryogenesis while the same model with a pseudoscalar mediator is able to explain the baryon asymmetry. For the latter, we constrain more the model with {\it Fermi}-LAT upper limit on dark matter annihilation into $b\bar{b}$ and ${\tau }^{+}{\tau }^{-}$. The allowed dark matter mass that leads to correct relic abundance, renders the electroweak phase transition strongly first-order, and respects the {\it Fermi}-LAT limit, will be in the range $110-320$ GeV. The exotic and invisible Higgs decay bounds and the mono-jet search limit at the LHC do not affect the viable space of parameters.

   hep-phhep-thJHEP(2017)·38 citations
8. 08*

   Squark-mediated Higgs+jets production at the LHC

   J. Duarte (1) · C. Peña (1) · A. Wang (1) M. Pierini (2) · M. Spiropulu (1) ((1) California Institute of Technology, (2) CERN)

   We investigate possible scenarios of light-squark production at the LHC as a new mechanism to produce Higgs bosons in association with jets. The study is motivated by the SUSY search for H+jets events, performed by the CMS collaboration on 8 and 13 TeV data using the razor variables. Two simplified models are proposed to interpret the observations in this search. The constraint from Run I and the implications for Run II and beyond are discussed.

   hep-phhep-ex5 citations
9. 09*

   Gravitational waves from a supercooled electroweak phase transition and their detection with pulsar timing arrays

   Archil Kobakhidze🇦🇺 · Cyril Lagger🇦🇺 · Adrian Manning🇦🇺 · Jason Yue🇹🇼

   We investigate the properties of a stochastic gravitational wave background produced by a first-order electroweak phase transition in the regime of extreme supercooling. We study a scenario whereby the percolation temperature that signifies the completion of the transition, $T_p$, can be as low as a few MeV (nucleosynthesis temperature), while most of the true vacuum bubbles are formed much earlier at the nucleation temperature, $T_n\sim 50$ GeV. This implies that the gravitational wave spectrum is mainly produced by the collisions of large bubbles and characterised by a large amplitude and a peak frequency as low as $f\sim 10^{-9}-10^{-7}$ Hz. We show that such a scenario can occur in (but not limited to) a model based on a non-linear realisation of the electroweak gauge group, such that the Higgs vacuum configuration is altered by a cubic coupling. In order to carefully quantify the evolution of the phase transition of this model over such a wide temperature range, we go beyond the usual fast transition approximation, taking into account the expansion of the Universe as well as the behaviour of the nucleation probability at low temperatures. Our computation shows that there exists a range of parameters for which the gravitational wave spectrum lies at the edge between the exclusion limits of current pulsar timing array experiments and the detection band of the future Square Kilometre Array observatory.

   hep-phgr-qcEPJC(2017)·116 citations
10. 10*

    Charmonium production in ultra-peripheral heavy ion collisions with two-photon processes

    Gong-Ming Yu🇨🇳 · Yue-Chao Yu🇨🇳 · Yun-De Li🇨🇳 · Jian-Song Wang🇨🇳

    We calculate the production of large-pTcharmonium and narrow resonance state (exotic charmonium) in proton-proton, proton-nucleus, and nucleus-nucleus collisions with the semi-coherent two-photon interactions at Relativistic Heavy Ion Collider (RHIC), Large Hadron Collider (LHC), and Future Circular Collider (FCC) energies. Using the large quasi-real photon fluxes, we present the \gamma\gamma->H differential cross section for charmonium and narrow resonance state production at large transverse momentum in ultra-peripheral heavy ion collisions. The numerical results demonstrate that the experimental study of ultra-peripheral col-lisions is feasible at RHIC, LHC, and FCC energies.

    hep-phnucl-thNPB(2017)·16 citations
11. 11*

    Multiphoton annihilation of monopolium

    Huner Fanchiotti🇦🇷 · Carlos A. García Canal🇦🇷 · Vicente Vento🇪🇸

    We show that due to the large coupling constant of the monopole-photon interaction the annihilation of monopole-antimonopole and monopolium into many photons must be considered experimentally. For monopole-antimonopole annihilation and lightly bound monopolium, even in the less favorable scenario, multi-photon events (four and more photons in the final state) are dominant, while for strongly bound monopolium, although two photon events are important, four and six photon events are also sizable.

    hep-phInt.J.Mod.Phys.A(2017)·19 citations
12. 12*

    Colormagnetic confinement in the quark-gluon thermodynamics

    M.S. Lukashov🇷🇺 · Yu.A. Simonov🇷🇺

    Nonperturbative effects in the quark-gluon thermodynamics are studied in the framework of Vacuum Correlator Method. It is shown, that two correlators: colorelectric $D_1^E(x)$ and colormagnetic $D^H(x)$, provide the Polyakov line and the colormagnetic confinement in the spatial planes respectively. As a result both effects produce the realistic behavior of $P(T)$ and $s(T)$, being in good agreement with numerical lattice data.

    hep-phhep-latJETP Lett.(2017)·9 citations
13. 13*

    Higgs decay into four charged leptons in the presence of dimension-six operators

    S. Boselli🇮🇹 · C.M. Carloni Calame🇮🇹 · G. Montagna🇮🇹 · O. Nicrosini🇮🇹 · F. Piccinini🇮🇹 · A. Shivaji🇮🇹

    We study the indirect effects of New Physics in the Higgs decay into four charged leptons, using an Effective Field Theory (EFT) approach to Higgs interactions. We evaluate the deviations induced by the EFT dimension-six operators in observables like partial decay width and various kinematic distributions, including angular observables, and compare them with the contribution of the full SM electroweak corrections. The calculation is implemented in an improved version of the event generator Hto4l, which can provide predictions in terms of different EFT-bases and is available for data analysis at the LHC. We also perform a phenomenological study in order to assess the benefits coming from the inclusion of differential information in the future analyses of very precise data which will be collected during the high luminosity phase of the LHC.

    hep-phhep-exJHEP(2018)·40 citations
14. 14*

    Common Origin of Non-zero ${\theta }_{13}$ and Dark Matter in an $S_4$ Flavour Symmetric Model with Inverse Seesaw

    Ananya Mukherjee🇮🇳 · Debasish Borah🇮🇳 · Mrinal Kumar Das🇮🇳

    We study an inverse seesaw model of neutrino mass within the framework of $S_4$ flavour symmetry from the requirement of generating non-zero reactor mixing angle ${\theta }_{13}$ along with correct dark matter relic abundance. The leading order $S_4$ model gives rise to tri-bimaximal type leptonic mixing resulting in ${\theta }_{13}=0$. Non-zero ${\theta }_{13}$ is generated at one loop level by extending the model with additional scalar and fermion fields which take part in the loop correction. The particles going inside the loop are odd under an in-built $Z_2^{\text{Dark}}$ symmetry such that the lightest $Z_2^{\text{Dark}}$ odd particle can be a dark matter candidate. Correct neutrino and dark matter phenomenology can be achieved for such one loop corrections either to the light neutrino mass matrix or to the charged lepton mass matrix although the latter case is found to be more predictive. The predictions for neutrinoless double beta decay is also discussed and inverted hierarchy in the charged lepton correction case is found to be disfavoured by the latest KamLAND-Zen data.

    hep-phastro-ph.COPRD(2017)·14 citations
15. 15*

    Charged Higgs Signals in $t\overline{t}H$ Searches

    Daniele S. M. Alves🇺🇸 · Sonia El Hedri🇩🇪 · Anna Maria Taki🇺🇸 · Neal Weiner🇺🇸

    New scalars from an extended Higgs sector could have weak scale masses and still have escaped detection. In a Type I Two Higgs Doublet Model, for instance, even the charged Higgs can be lighter than the top quark. Because electroweak production of these scalars is modest, the greatest opportunity for their detection might come from rare top decays. For mass hierarchies of the type $m_t>m_{H^{\pm }}>m_{A^0,H^0}$, the natural signal can arise from top quark pair production, followed by the decay chain $t\to b{H}^{+}$, $H^{+}\to W^{+(\ast )}{\varphi }^0$, ${\varphi }^0\to b\overline{b},{\tau }^{+}{\tau }^{-}$, where ${\varphi }^0=A^0,H^0$. These final states largely overlap with those of the Standard Model $t\bar{t}{H}_{{}_{\text{SM}}}^0$ process, and therefore can potentially contaminate $t\bar{t}{H}_{{}_{\text{SM}}}^0$ searches. We demonstrate that existing $t\bar{t}{H}_{{}_{\text{SM}}}^0$ analyses can already probe light extended Higgs sectors, and we derive new constraints from their results. Furthermore, we note that existing excesses in $t\bar{t}{H}_{{}_{\text{SM}}}^0$ searches can be naturally explained by the contamination of rare top decays to new light Higgses. We discuss how to distinguish this signal from the Standard Model process.

    hep-phhep-exPRD(2017)·10 citations
16. 16*

    Thermalization time scales for WIMP capture by the Sun in effective theories

    Axel Widmark🇸🇪

    I study the process of dark matter capture by the Sun, under the assumption of a Weakly Interacting Massive Particle (WIMP), in the framework of non-relativistic effective field theory. Hypothetically, WIMPs from the galactic halo can scatter against atomic nuclei in the solar interior, settle to thermal equilibrium with the solar core and annihilate to produce an observable flux of neutrinos. In particular, I examine the thermalization process using Monte-Carlo integration of WIMP trajectories. I consider WIMPs in a mass range of 10--1000 GeV and WIMP-nucleon interaction operators with different dependence on spin and transferred momentum. I find that the density profiles of captured WIMPs are in accordance with a thermal profile described by the Sun's gravitational potential and core temperature. Depending on the operator that governs the interaction, the majority of the thermalization time is spent in either the solar interior or exterior. If normalizing the WIMP-nuclei interaction strength to a specific capture rate, I find that the thermalization time differs at most by 3 orders of magnitude between operators. In most cases of interest, the thermalization time is many orders of magnitude shorter than the age of the solar system.

    hep-phastro-ph.COJCAP(2017)·26 citations
17. 17*

    Testing Light Dark Matter Coannihilation With Fixed-Target Experiments

    Eder Izaguirre🇺🇸 · Yonatan Kahn🇺🇸 · Gordan Krnjaic🇺🇸 · Matthew Moschella🇺🇸

    In this paper, we introduce a novel program of fixed-target searches for thermal-origin Dark Matter (DM), which couples inelastically to the Standard Model. Since the DM only interacts by transitioning to a heavier state, freeze-out proceeds via coannihilation and the unstable heavier state is depleted at later times. For sufficiently large mass splittings, direct detection is kinematically forbidden and indirect detection is impossible, so this scenario can only be tested with accelerators. Here we propose new searches at proton and electron beam fixed-target experiments to probe sub-GeV coannihilation, exploiting the distinctive signals of up- and down-scattering as well as decay of the excited state inside the detector volume. We focus on a representative model in which DM is a pseudo-Dirac fermion coupled to a hidden gauge field (dark photon), which kinetically mixes with the visible photon. We define theoretical targets in this framework and determine the existing bounds by reanalyzing results from previous experiments. We find that LSND, E137, and BaBar data already place strong constraints on the parameter space consistent with a thermal freeze-out origin, and that future searches at Belle II and MiniBooNE, as well as recently-proposed fixed-target experiments such as LDMX and BDX, can cover nearly all remaining gaps. We also briefly comment on the discovery potential for proposed beam dump and neutrino experiments which operate at much higher beam energies.

    hep-phhep-exPRD(2017)·133 citations
18. 18*

    Viable Twin Cosmology from Neutrino Mixing

    Csaba Csaki🇺🇸 · Eric Kuflik🇺🇸 · Salvator Lombardo🇺🇸

    Twin Higgs models solve the little hierarchy problem without introducing new colored particles, however they are often in tension with measurements of the radiation density at late times. Here we explore viable cosmological histories for Twin Higgs models. In particular, we show that mixing between the SM and twin neutrinos can thermalize the two sectors below the twin QCD phase transition, significantly reducing the twin sector's contribution to the radiation density. The requisite twin neutrino masses of order 1-20 GeV and mixing angle with SM neutrinos of 10^{-3} - 10^{-5} can be probed in a variety of current and planned experiments. We further find that these parameters can be naturally accessed in a warped UV completion, where the neutrino sector can also generate the Z2-breaking Higgs mass term needed to produce the hierarchy between the symmetry breaking scales f and v.

    hep-phPRD(2017)·63 citations
19. 19*

    Testing Invisible Momentum Ansatze in Missing Energy Events at the LHC

    Doojin Kim🇨🇭 · Konstantin T. Matchev🇺🇸 · Filip Moortgat🇨🇭 · Luc Pape🇨🇭

    We consider SUSY-like events with two decay chains, each terminating in an invisible particle, whose true energy and momentum are not measured in the detector. Nevertheless, a useful educated guess about the invisible momenta can still be obtained by optimizing a suitable invariant mass function. We review and contrast several proposals in the literature for such ansatze: four versions of the M_T2-assisted on-shell reconstruction (MAOS), as well as several variants of the on-shell constrained M_2 variables. We compare the performance of these methods with regards to the mass determination of a new particle resonance along the decay chain from the peak of the reconstructed invariant mass distribution. For concreteness, we consider the event topology of dilepton ttbar events and study each of the three possible subsystems, in both a ttbar and a SUSY example. We find that the M_2 variables generally provide sharper peaks and therefore better ansatze for the invisible momenta. We show that the performance can be further improved by preselecting events near the kinematic endpoint of the corresponding variable from which the momentum ansatz originates.

    hep-phhep-exJHEP(2017)·19 citations
20. 20*

    Updated Constraints on the Dark Matter Interpretation of CDMS-II-Si Data

    Samuel J. Witte🇺🇸 · Graciela B. Gelmini🇺🇸

    We present an updated halo-dependent and halo-independent analysis of viable light WIMP dark matter candidates which could account for the excess observed in CDMS-II-Si. We include recent constraints from LUX, PandaX-II, and PICO-60, as well as projected sensitivities for XENON1T, SuperCDMS SNOLAB, LZ, DARWIN, DarkSide-20k, and PICO-250, on candidates with spin-independent isospin conserving and isospin-violating interactions, and either elastic or exothermic scattering. We show that there exist dark matter candidates which can explain the CDMS-II-Si data and remain very marginally consistent with the null results of all current experiments, however such models are highly tuned, making a dark matter interpretation of CDMS-II-Si very unlikely. We find that these models can only be ruled out in the future by an experiment comparable to LZ or PICO-250.

    hep-phastro-ph.COJCAP(2017)·24 citations
21. 21*

    Dilepton radiation and bulk viscosity in heavy-ion collisions

    Gojko Vujanovic🇺🇸 · Jean-François Paquet🇺🇸 · Chun Shen🇺🇸 · Gabriel S. Denicol🇧🇷 · Sangyong Jeon🇨🇦 · Charles Gale🇨🇦 · Ulrich Heinz🇺🇸

    Starting from IP-Glasma initial conditions, we investigate the effects of bulk pressure on thermal dilepton production at the Relativistic Heavy Ion Collider (RHIC) and the Large Hadron Collider (LHC) energies. Though results of the thermal dilepton $v_2$ under the influence of both bulk and shear viscosity is presented for top RHIC energy, more emphasis is put on LHC energy where such a calculation is computed for the first time. The effects of the bulk pressure on thermal dilepton $v_2$ at the LHC are explored through bulk-induced modifications on the dilepton yield.

    ↳ nucl-thhep-phnucl-exNucl.Part.Phys.Proc.(2017)·5 citations
22. 22*

    Phases of circle-compactified QCD with adjoint fermions at finite density

    Takuya Kanazawa🇯🇵 · Mithat Ünsal🇺🇸 · Naoki Yamamoto🇯🇵

    We study chemical-potential dependence of confinement and mass gap in QCD with adjoint fermions in spacetime with one spatial compact direction. By calculating the one-loop effective potential for the Wilson line in the presence of chemical potential, we show that a center-symmetric phase and a center-broken phase alternate when the chemical potential in unit of the compactification scale is increased. In the center-symmetric phase we use semiclassical methods to show that photons in the magnetic bion plasma acquire a mass gap that grows with the chemical potential as a result of anisotropic interactions between monopole-instantons. For the neutral fermionic sector which remains gapless perturbatively, there are two possibilities at non-perturbative level. Either to remain gapless (unbroken global symmetry), or to undergo a novel superfluid transition through a four-fermion interaction (broken global symmetry). If the latter is the case, this leads to an energy gap of quarks proportional to a new nonperturbative scale $L^{-1}\exp [-1/(g^4\mu L)]$, where $L$ denotes the circumference of $S^1$, the low-energy is described as a Nambu-Goldstone mode associated with the baryon number, and there exists a new type of BEC-BCS crossover of the diquark pairing as a function of the compactification scale at small chemical potential.

    ↳ hep-thhep-lathep-phPRD(2017)·8 citations
23. 23*

    On the Apparent Ambiguities in the Post-Newtonian Expansion for Binary Systems

    Rafael A. Porto🇧🇷 · Ira Z. Rothstein🇺🇸

    We discuss the source of the apparent ambiguities arising in the calculation of the dynamics of binary black holes within the Post-Newtonian framework. Divergences appear in both the near and far zone calculations, and may be of either ultraviolet (UV) or infrared (IR) nature. The effective field theory (EFT) formalism elucidates the origin of the singularities which may introduce apparent ambiguities. In particular, the only (physical) 'ambiguity parameters' that necessitate a matching calculation correspond to unknown finite size effects, which first appear at fifth Post-Newtonian (5PN) order for non-spinning bodies. We demonstrate that the ambiguities linked to IR divergences in the near zone, that plague the recent derivations of the binding energy at 4PN order, both in the ADM and 'Fokker-action' approach, can be resolved by implementing the so-called 'zero-bin' subtraction in the EFT framework. The procedure yields ambiguity-free results without the need of additional information beyond the PN expansion.

    ↳ gr-qchep-phhep-thPRD(2017)·106 citations
24. 24*

    The Lamb shift and the gravitational binding energy for binary black holes

    Rafael A. Porto🇧🇷

    We show that the correction to the gravitational binding energy for binary black holes due to the tail effect resembles the Lamb shift in the Hydrogen atom. In both cases a 'conservative' effect arises from interactions with 'radiation' modes, and moreover an explicit cancelation between near and far zone divergences is at work. In addition, regularization scheme-dependence may introduce ambiguity parameters. This is remediated, within an effective field theory approach, by the implementation of the zero-bin subtraction. We illustrate the procedure explicitly for the Lamb shift, by performing an ambiguity-free derivation within the framework of non-relativistic electrodynamics. We also derive the renormalization group equations from which we reproduce Bethe logarithm (at order ${\alpha }_e^5\log {\alpha }_e$), and likewise the contribution to the gravitational potential from the tail effect (proportional to $v^8\log v$).

    ↳ gr-qchep-phhep-thPRD(2017)·34 citations
25. 25*

    The Music of the Spheres: The Dawn of Gravitational Wave Science

    Rafael A. Porto🇧🇷

    The LIGO results are among the greatest experimental achievements of all times. Time and again scientists have compared this feat to Galileo pointing his telescope to the sky, offering instead an 'ear' to the cosmos. After the remarkable landmark of detection, the physics community will soon turn into the study of the properties of the sources, addressing fundamental questions in astrophysics and cosmology. A combined numerical and analytic effort to tackle the binary problem is of paramount importance in light of the nascent program of multi-messenger astronomy. The century of gravitational wave science is in the making, and many discoveries are yet to come in the advent of a new era of 'precision gravity'.

    ↳ physics.pop-phgr-qchep-phhep-th21 citations
26. 26*

    Influence of the hadronic phase on observables in ultrarelativistic heavy ion collisions

    J. Steinheimer🇩🇪 · J. Aichelin🇫🇷 · M. Bleicher🇩🇪 · H. Stöcker🇩🇪

    The hadronic phase in ultrarelativistic nuclear collisions has a large influence on final state observables like multiplicity, flow and $p_t$ spectra, as studied in the UrQMD approach. In this model one assumes that a non-equilibrium decoupling phase follows a fluid dynamical description of the high density phase. Hadrons are produced assuming local thermal equilibrium and dynamically decouple during the hadronic rescattering until the particles are registered in the detectors. This rescattering of hadrons modifies every hadronic bulk observable. The apparent multiplicity of resonances is suppressed as compared to a chemical equilibrium freeze-out model, because the decay products rescatter. Therefore the resonances, which decay in the early hadronic phase, cannot be identified anymore by the invariant mass method. Stable and unstable particles change their momentum distribution by more than 30$\%$ through rescattering and their multiplicity is modified by resonance production and annihilation on a similar magnitude. These findings show that it is all but trivial to conclude from the final state observables on the properties of the system at an earlier time where it may have been in local equilibrium.

    ↳ nucl-thhep-phPRC(2017)·52 citations
27. 27*

    QCD thermodynamics in the crossover/freeze-out region

    Frithjof Karsch🇩🇪

    We use results from a 6-th order Taylor expansion of the QCD equation of state to construct expansions for cumulants of conserved charge fluctuations and their correlations. We show that these cumulants strongly constrain the range of applicability of hadron resonance gas model calculations. We point out that the latter is inappropriate to describe equilibrium properties of QCD at zero and non-zero values of the baryon chemical potential already at T~155 MeV.

    ↳ hep-lathep-phActa Phys.Polon.Supp.(2017)·8 citations
28. 28*

    Up, down, and strange nucleon axial form factors from lattice QCD

    Jeremy Green🇩🇪 · Nesreen Hasan🇩🇪 · Stefan Meinel🇺🇸 · Michael Engelhardt🇺🇸 · Stefan Krieg🇩🇪 · Jesse Laeuchli🇺🇸 · John Negele🇺🇸 · Kostas Orginos🇺🇸 · Andrew Pochinsky🇺🇸 · Sergey Syritsyn🇺🇸

    We report a calculation of the nucleon axial form factors $G_A^q(Q^2)$ and $G_P^q(Q^2)$ for all three light quark flavors $q\in \{u,d,s\}$ in the range $0\le Q^2\lesssim 1.2{\text{ GeV}}^2$ using lattice QCD. This work was done using a single ensemble with pion mass 317 MeV and made use of the hierarchical probing technique to efficiently evaluate the required disconnected loops. We perform nonperturbative renormalization of the axial current, including a nonperturbative treatment of the mixing between light and strange currents due to the singlet-nonsinglet difference caused by the axial anomaly. The form factor shapes are fit using the model-independent $z$ expansion. From $G_A^q(Q^2)$, we determine the quark contributions to the nucleon spin and axial radii. By extrapolating the isovector $G_P^{u-d}(Q^2)$, we obtain the induced pseudoscalar coupling relevant for ordinary muon capture and the pion-nucleon coupling constant. We find that the disconnected contributions to $G_P$ form factors are large, and give an interpretation based on the dominant influence of the pseudoscalar poles in these form factors.

    ↳ hep-lathep-phnucl-thPRD(2017)·114 citations
29. 29*

    Gamma Ray Burst afterglow and prompt-afterglow relations: an overview

    Maria Dainotti · Roberta Del Vecchio

    The mechanism responsible for the afterglow emission of Gamma Ray Bursts (GRBs) and its connection to the prompt $\gamma$-ray emission is still a debated issue. Relations between intrinsic properties of the prompt or afterglow emission can help to discriminate between plausible theoretical models of GRB production. Here we present an overview of the afterglow and prompt-afterglow two parameter relations, their physical interpretations, their use as redshift estimators and as possible cosmological tools. A similar task has already been correctly achieved for Supernovae (SNe) Ia by using the peak magnitude-stretch relation, known in the literature as the Phillips relation \citep{phillips93}. The challenge today is to make GRBs, which are amongst the farthest objects ever observed, standardizable candles as the SNe Ia through well established and robust relations. Thus, the study of relations amongst the observable and physical properties of GRBs is highly relevant together with selection biases in their physical quantities. Therefore, we describe the state of the art of the existing GRB relations, their possible and debated interpretations in view of the current theoretical models and how relations are corrected for selection biases. We conclude that only after an appropriate evaluation and correction for selection effects can GRB relations be used to discriminate among the theoretical models responsible for the prompt and afterglow emission and to estimate cosmological parameters.

    ↳ astro-ph.HEhep-phNew Astron.Rev.(2017)·85 citations
30. 30*

    Theory and applications of free-electron vortex states

    K. Y. Bliokh🇯🇵 · I. P. Ivanov🇵🇹 · G. Guzzinati🇧🇪 · L. Clark🇬🇧 · R. Van Boxem🇧🇪 · A. Béché🇧🇪 · R. Juchtmans🇧🇪 · M. A. Alonso🇺🇸 · P. Schattschneider🇦🇹 · F. Nori🇺🇸 · J. Verbeeck🇧🇪

    Both classical and quantum waves can form vortices: with helical phase fronts and azimuthal current densities. These features determine the intrinsic orbital angular momentum carried by localized vortex states. In the past 25 years, optical vortex beams have become an inherent part of modern optics, with many remarkable achievements and applications. In the past decade, it has been realized and demonstrated that such vortex beams or wavepackets can also appear in free electron waves, in particular, in electron microscopy. Interest in free-electron vortex states quickly spread over different areas of physics: from basic aspects of quantum mechanics, via applications for fine probing of matter (including individual atoms), to high-energy particle collision and radiation processes. Here we provide a comprehensive review of theoretical and experimental studies in this emerging field of research. We describe the main properties of electron vortex states, experimental achievements and possible applications within transmission electron microscopy, as well as the possible role of vortex electrons in relativistic and high-energy processes. We aim to provide a balanced description including a pedagogical introduction, solid theoretical basis, and a wide range of practical details. Special attention is paid to translate theoretical insights into suggestions for future experiments, in electron microscopy and beyond, in any situation where free electrons occur.

    ↳ quant-phhep-phhep-thphysics.opticsPhys.Rept.(2017)·219 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.