Fri·Oct 28, 2016Friday·October 28, 2016

1. 01*

   Graviton resonance phenomenology and a pNGB Higgs at the LHC

   Ezequiel Alvarez (ICAS, Argentina)🇦🇷 · Leandro Da Rold (CAB, Argentina)🇦🇷 · Javier Mazzitelli (ICAS, Argentina and U. Zurich, Switzerland)🇦🇷 · Alejandro Szynkman (UNLP, Argentina)🇦🇷

   We present an effective description of a spin two massive state and a pseudo Nambu-Goldstone boson Higgs in a two site model. Using this framework we model the spin two state as a massive graviton and we study its phenomenology at the LHC. We find that a reduced set of parameters can describe the most important features of this scenario. We address the question of which channel is the most sensitive to detect this graviton. Instead of designing search strategies to estimate the significance in each channel, we compare the ratio of our theoretical predictions to the limits set by available experimental searches for all the decay channels and as a function of the free parameters in the model. We discuss the phenomenological details contained in the outcome of this simple procedure. The results indicate that, for the studied masses between 0.5 and 3 TeV, the channels to look for such a graviton resonance are mainly $ZZ$, $WW$ and $\gamma \gamma$. This is the case even though top and bottom quarks dominate the branching ratios, since their experimental sensitivity is not as good as the one of the electro-weak gauge bosons. We find that as the graviton mass increases, the $ZZ$ and $WW$ channels become more important because of its relatively better enhancement over background, mainly due to fat jet techniques. We determine the region of the parameter space that has already been excluded and the reach for the LHC next stages. We also estimate the size of the loop-induced contributions to the production and decay of the graviton, and show in which region of the parameter space their effects are relevant for our analysis.

   hep-phhep-exPRD(2017)·10 citations
2. 02*

   MeV-scale sterile neutrino decays at the Fermilab Short-Baseline Neutrino program

   Peter Ballett🇬🇧 · Silvia Pascoli🇬🇧 · Mark Ross-Lonergan🇬🇧

   Nearly-sterile neutrinos with masses in the MeV range and below would be produced in the beam of the Short-Baseline Neutrino (SBN) program at Fermilab. In this article, we study the potential for SBN to discover these particles through their subsequent decays in its detectors. We discuss the decays which will be visible at SBN in a minimal and non-minimal extension of the Standard Model, and perform simulations to compute the parameter space constraints which could be placed in the absence of a signal. We demonstrate that the SBN program can extend existing bounds on well constrained channels such as $N\to \nu l^{+}{l}^{-}$ and $N\to l^{\pm }{\pi }^{\mp }$ while, thanks to the strong particle identification capabilities of liquid-Argon technology, also place bounds on often neglected channels such as $N\to \nu \gamma$ and $N\to \nu {\pi }^0$. Furthermore, we consider the phenomenological impact of improved event timing information at the three detectors. As well as considering its role in background reduction, we note that if the light-detection systems in SBND and ICARUS can achieve nanosecond timing resolution, the effect of finite sterile neutrino mass could be directly observable, providing a smoking-gun signature for this class of models. We stress throughout that the search for heavy nearly-sterile neutrinos is a complementary new physics analysis to the search for eV-scale oscillations, and would extend the BSM program of SBN while requiring no beam or detector modifications.

   hep-phJHEP(2017)·79 citations
3. 03*

   Tracing the pressure of the gluon plasma

   G. Jackson🇿🇦 · A. Peshier🇿🇦

   Being interested in how a strongly coupled system approaches asymptotic freedom, we re-examine existing precision lattice QCD results for thermodynamic properties of the gluon plasma in a large temperature range. We discuss and thoroughly test the applicability of perturbative results, on which grounds we then infer that the pressure and other bulk properties approach the free limit somewhat slower than previously thought. We also revise the value of the first non-perturbative coefficient in the weak-coupling expansion.

   hep-phhep-latnucl-thPRD(2017)·1 citation
4. 04*

   Charm Quark Mass with Calibrated Uncertainty

   Jens Erler🇲🇽 · Pere Masjuan🇪🇸 · Hubert Spiesberger🇩🇪

   We determine the charm quark mass ${\hat{m}}_c$ from QCD sum rules of moments of the vector current correlator calculated in perturbative QCD at $\mathcal{O}({\hat{\alpha }}_s^3)$. Only experimental data for the charm resonances below the continuum threshold are needed in our approach, while the continuum contribution is determined by requiring self-consistency between various sum rules. Existing data from the continuum region can then be used to bound the theoretic uncertainty. Our result is ${\hat{m}}_c({\hat{m}}_c)=1272\pm 8$~MeV for ${\hat{\alpha }}_s(M_Z)=0.1182$.

   hep-phEPJC(2017)·27 citations
5. 05*

   Higgs Effective Field Theories - Systematics and Applications

   Claudius Krause🇩🇪

   We discuss effective field theories (EFTs) for the Higgs particle, which is not necessarily the Higgs of the Standard Model. We distinguish two different consistent expansions: EFTs that describe decoupling new-physics effects and EFTs that describe non-decoupling new-physics effects. We briefly discuss the first case, the SM-EFT. The focus of this thesis is on the non-decoupling EFTs. We argue that the loop expansion is the consistent expansion in the second case. We introduce the concept of chiral dimensions, equivalent to the loop expansion. Using the chiral dimensions, we expand the electroweak chiral Lagrangian up to next-to-leading order, $\mathcal{O}(f^2/{\Lambda }^2)=\mathcal{O}(1/16{\pi }^2)$. We then compare the decoupling and the non-decoupling EFT. We also consider scenarios in which the new-physics sector is non-decoupling at a scale $f$, far above the electroweak-scale $v$. We discuss the relevance of the resulting double expansion in $\xi =v^2/f^2$ and $f^2/{\Lambda }^2$ for the data analysis at the LHC. In the second part, we discuss the applications of the EFTs, especially of the electroweak chiral Lagrangian. First, we connect the EFT with explicit models of new physics. We show how different regions of the parameter space of the same model generate a decoupling and a non-decoupling EFT. Second, we use the expansion at leading order to describe the current LHC Higgs data. We show how the current parametrization of the Higgs data, the $\kappa$-framework, can be justified quantum field theoretically by the EFT. We fit the data of Run-1 (2010--2013). The effective Lagrangian describing this data can be reduced to six free parameters. The result of this fit is consistent with the SM, but it has statistical uncertainties of about ten percent.

   hep-ph16 citations
6. 06*

   Diphoton production in lead-lead and proton-proton UPC

   Mariola Klusek-Gawenda🇵🇱 · Antoni Szczurek🇵🇱

   We discuss diphoton semi(exclusive) production in ultraperipheral $PbPb$ collisions at energy of $\sqrt{s_{NN}}=$ 5.5 TeV (LHC). The nuclear calculations are based on equivalent photon approximation in the impact parameter space. The cross sections for elementary $\gamma \gamma \to \gamma \gamma$ subprocess are calculated including three different mechanisms: box diagrams with leptons and quarks in the loops, a VDM-Regge contribution with virtual intermediate hadronic excitations of the photons and the two-gluon exchange contribution (formally three-loops) to elastic photon-photon scattering in the high-energy approximation. We got relatively high cross sections in $PbPb$ collisions ($306$ nb). This opens a possibility to study the $\gamma \gamma \to \gamma \gamma$ (quasi)elastic scattering at the LHC. We find that the cross section for elastic $\gamma \gamma$ scattering could be measured in the lead-lead collisions for the diphoton invariant mass up to $W_{\gamma \gamma }\approx 15-20$ GeV. We identify region(s) of phase space where the two-gluon exchange contribution becomes important ingredient compared to box and nonperturbative VDM-Regge mechanisms. We perform a similar analysis for the $pp\to pp\gamma \gamma$ reaction at energy of $\sqrt{s_{NN}}=7$ and $100$ TeV.

   hep-ph1 citation
7. 07*

   Ordered Kinematic Endpoints for 5-body Cascade Decays

   Matthew D. Klimek🇺🇸

   We present expressions for the kinematic endpoints of 5-body cascade decay chains proceeding through all possible combinations of 2-body and 3-body decays, with one stable invisible particle in the final decay stage. When an invariant mass can be formed in multiple ways by choosing different final state particles from a common vertex, we introduce techniques for finding the sub-leading endpoints for all indistinguishable versions of the invariant mass. In contrast to short decay chains, where sub-leading endpoints are linearly related to the leading endpoints, we find that in 5-body decays, they provide additional independent constraints on the mass spectrum.

   hep-phhep-exJHEP(2016)·5 citations
8. 08*

   Light-Cone Singularities and Transverse-Momentum-Dependent Factorization at Twist-3

   A.P. Chen🇨🇳 · J.P. Ma🇨🇳

   We study transverse-momentum-dependent factorization at twist-3 for Drell-Yan processes. The factorization can be derived straightforwardly at leading order of ${\alpha }_s$. But at this order we find that light-cone singularities already exist and effects of soft gluons are not correctly factorized. We regularize the singularities with gauge links off the light-cone and introduce a soft factor to factorize the effects of soft gluons. Interestingly, the soft factor must be included in the definition of subtracted TMD parton distributions to correctly factorize the effects of soft gluons. We derive the Collins-Soper equation for one of twist-3 TMD parton distributions. The equation can be useful for resummation of large logarithms terms appearing in the corresponding structure function in collinear factorization. However, the derived equation is nonhomogeneous. This will make the resummation complicated.

   hep-phPLB(2017)·10 citations
9. 09*

   Geometric phase of neutrinos: differences between Dirac and Majorana neutrinos

   A. Capolupo🇮🇹 · S.M. Giampaolo🇧🇷 · B. C. Hiesmayr🇦🇹 · G. Vitiello🇮🇹

   We analize the non-cyclic geometric phase for neutrinos. We find that the geometric phase and the total phase associated to the mixing phenomenon provide a tool to distinguish between Dirac and Majorana neutrinos. Our results hold for neutrinos propagating in vacuum and through the matter. Future experiments, based on interferometry, could reveal the nature of neutrinos.

   hep-phPLB(2018)·37 citations
10. 10*

    Isospin-violating dark matter in the light of recent data

    Carlos E. Yaguna🇩🇪

    In scenarios where the dark matter interacts differently with protons and neutrons (isospin-violating dark matter), the interpretation of the experimental limits on the dark matter spin-independent cross section may be significantly modified. On the one hand, the direct detection constraints are shifted depending on the target nucleus, possibly changing the hierarchy among different experiments. On the other hand, the relative strength between the bounds from neutrino detectors and those from direct detection experiments is altered, allowing the former to be more competitive. In this paper, the status of isospin-violating dark matter is assessed in the light of recent data, and the prospects for its detection in the near future are analyzed. We find, for example, that there are regions in the parameter space where IceCube currently provides the most stringent limits on the spin-independent cross section, or others where the expected sensitivity of DEAP-3600 is well above the LUX exclusion limit. Our results highlight the complementarity among different targets in direct detection experiments, and between direct detection and neutrino searches in the quest for a dark matter signal.

    hep-phPRD(2017)·34 citations
11. 11*

    Fluctuation-induced modifications of the phase structure in (2+1)-flavor QCD

    Fabian Rennecke🇩🇪 · Bernd-Jochen Schaefer🇩🇪

    The low-energy sector of QCD with $N_f=2+1$ dynamical quark flavors at non-vanishing chemical potential and temperature is studied with a non-perturbative functional renormalization group method. The analysis is performed in different truncations in order to explore fluctuation-induced modifications of the quark-meson correlations as well as quark and meson propagators on the chiral phase transition of QCD. Depending on the chosen truncation significant quantitative implications on the phase transition are found. In the chirally symmetric phase, the quark flavor composition of the pseudoscalar $(\eta ,{\eta }^{\prime })$-meson complex turns out to be drastically sensitive to fluctuation-induced modifications in the presence of the axial $U(1{)}_A$ anomaly. This has important phenomenological consequences for the assignment of chiral partners to these mesons.

    hep-phhep-thnucl-thPRD(2017)·87 citations
12. 12*

    In-Medium Spectral Functions of Vector- and Axial-Vector Mesons from the Functional Renormalization Group

    Christopher Jung🇩🇪 · Fabian Rennecke🇩🇪 · Ralf-Arno Tripolt🇮🇹 · Lorenz von Smekal🇩🇪 · Jochen Wambach🇮🇹

    In this work we present first results on vector and axial-vector meson spectral functions as obtained by applying the non-perturbative functional renormalization group approach to an effective low-energy theory motivated by the gauged linear sigma model. By using a recently proposed analytic continuation method, we study the in-medium behavior of the spectral functions of the $\rho$ and $a_1$ mesons in different regimes of the phase diagram. In particular, we demonstrate explicitly how these spectral functions degenerate at high temperatures as well as at large chemical potentials, as a consequence of the restoration of chiral symmetry. In addition, we also compute the momentum dependence of the $\rho$ and $a_1$ spectral functions and discuss the various time-like and space-like processes that can occur.

    hep-phPRD(2017)·100 citations
13. 13*

    Lorentz violation and deep inelastic scattering

    Alan Kostelecky🇺🇸 · E. Lunghi🇺🇸 · A.R. Vieira🇺🇸

    The effects of quark-sector Lorentz violation on deep inelastic electron-proton scattering are studied. We show that existing data can be used to establish first constraints on numerous coefficients for Lorentz violation in the quark sector at an estimated sensitivity of parts in a million.

    hep-phPLB(2017)·38 citations
14. 14*

    Measuring the Breaking of Lepton Flavour Universality in $B\to K^{\ast }{\ell }^{+}{\ell }^{-}$

    Nicola Serra🇨🇭 · Rafael Silva Coutinho🇨🇭 · Danny van Dyk🇨🇭

    We propose measurements of weighted differences of the angular observables in the rare decays $B\to K^{\ast }{\ell }^{+}{\ell }^{-}$. The proposed observables are very sensitive to the difference between the Wilson coefficients ${\mathcal{C}}_9^{(e)}$ and ${\mathcal{C}}_9^{(\mu )}$ for decays into electrons and muons, respectively. At the same time, the charm-induced hadronic contributions are kinematically suppressed to $\lesssim 7\%(4\%)$ in the region $1$GeV${}^2\le q^2\le 6$GeV${}^2$, as long as LFU breaking occurs only in ${\mathcal{C}}_9^{(\ell )}$. This suppression becomes stronger for the region of low hadronic recoil, $q^2\ge 15$GeV${}^2$.

    hep-phPRD(2017)·62 citations
15. 15*

    LHC vector resonance searches in the $t\bar{t}Z$ final state

    Mihailo Backović🇧🇪 · Thomas Flacke🇰🇷 · Bithika Jain🇰🇷 · Seung J. Lee🇰🇷

    LHC searches for BSM resonances in $l^{+}{l}^{-},jj,t\bar{t},\gamma \gamma$ and $VV$ final states have so far not resulted in discovery of new physics. Current results set lower limits on mass scales of new physics resonances well into the $\mathcal{O}(1)$ TeV range, assuming that the new resonance decays dominantly to a pair of Standard Model particles. While the SM pair searches are a vital probe of possible new physics, it is important to re-examine the scope of new physics scenarios probed with such final states. Scenarios where new resonances decay dominantly to final states other than SM pairs, even though well theoretically motivated, lie beyond the scope of SM pair searches. In this paper we argue that LHC searches for (vector) resonances beyond two particle final states would be useful complementary probes of new physics scenarios. As an example, we consider a class of composite Higgs models, and identify specific model parameter points where the color singlet, electrically neutral vector resonance ${\rho }_0$ decays dominantly not to a pair of SM particles, but to a fermionic top partner $T_{f1}$ and a top quark, with $T_{f1}\to tZ$. We show that dominant decays of ${\rho }_0\to T_{f1}t$ in the context of Composite Higgs models are possible even when the decay channel to a pair of $T_{f1}$ is kinematically open. Our analysis deals with scenarios where both $m_{\rho }$ and $m_{T_{f1}}$ are of $\mathcal{O}(1)$ TeV, leading to highly boosted $t\bar{t}Z$ final state topologies. We show that the particular composite Higgs scenario we consider is discoverable at the LHC13 with as little as 30 fb${}^{-1}$, while being allowed by other existing experimental constraints.

    hep-phhep-exJHEP(2017)·4 citations
16. 16*

    Meson cloud effects on the pion quark distribution function in the chiral constituent quark model

    Akira Watanabe🇹🇼 · Chung Wen Kao🇹🇼 · Katsuhiko Suzuki🇯🇵

    We investigate the valence quark distribution function of the pion $v^{\pi }(x,Q^2)$ in the framework of the chiral constituent quark model and evaluate the meson cloud effects on $v^{\pi }(x,Q^2)$. We explicitly demonstrate how the meson cloud effects affect $v^{\pi }(x,Q^2)$ in detail. We find that the meson cloud correction causes an overall 32\% reduction of the valence quark distribution and an enhancement at the small Bjorken $x$ regime. Besides, we also find that the dressing effect of the meson cloud will make the valence quark distribution to be softer in the large $x$ region.

    hep-phnucl-thPRD(2016)·24 citations
17. 17*

    Large scalar multiplet dark matter in the high-mass region

    Heather E. Logan🇨🇦 · Terry Pilkington🇨🇦

    We study two models of scalar dark matter from "large" electroweak multiplets with isospin 5/2 (n=6 members) and 7/2 (n=8), whose scalar potentials preserve a $Z_2$ symmetry. Because of large annihilation cross sections due to electroweak interactions, these scalars can constitute all the dark matter only for masses in the multi-TeV range. For such high masses, Sommerfeld enhancement and co-annihilations play important roles in the dark matter relic abundance calculation, reducing the upper bound on the large multiplet's mass by almost a factor of two. We determine the allowed parameter ranges including both of these effects and show that these models are as yet unconstrained by dark matter direct detection experiments, but will be probed by currently-running and proposed future experiments. We also show that a Landau pole appears in these models at energy scales below $10^9$ GeV, indicating the presence of additional new physics below that scale.

    hep-phastro-ph.COPRD(2017)·9 citations
18. 18*

    Optimal renormalization and the extraction of the strange quark mass from moments of the $\tau$-decay spectral function

    B. Ananthanarayan🇮🇳 · Diganta Das🇮🇳

    We introduce an optimal renormalization group analysis pertinent to the analysis of polarization functions associated with the $s$-quark mass relevant in $\tau$-decay. The technique is based on the renormalization group invariance constraints which lead to closed form summation of all the leading and next-to-leading logarithms at each order in perturbation theory. The new perturbation series exhibits reduced sensitivity to the renormalization scale and improved behavior in the complex plane along the integration contour. Using improved experimental and theory inputs, we have extracted the value of the strange quark mass $m_s(2\mathrm{GeV})=106.70\pm 9.36\mathrm{MeV}$ and $m_s(2\mathrm{GeV})=74.47\pm 7.77\mathrm{MeV}$ from presently available ALEPH and OPAL data respectively. These determinations are in agreement with the determinations in other phenomenological methods and from the lattice.

    hep-phPRD(2016)·13 citations
19. 19*

    Mass Generation, the Cosmological Constant Problem, Conformal Symmetry, and the Higgs Boson

    Philip D. Mannheim🇺🇸

    In 2013 the Nobel Prize in Physics was awarded to Francois Englert and Peter Higgs for their work in 1964 along with the late Robert Brout on the mass generation mechanism (the Higgs mechanism) in local gauge theories. This mechanism requires the existence of a massive scalar particle, the Higgs boson, and in 2012 the Higgs boson was finally discovered at the Large Hadron Collider after being sought for almost half a century. In this article we review the work that led to the discovery of the Higgs boson and discuss its implications. We approach the topic from the perspective of a dynamically generated Higgs boson that is a fermion-antifermion bound state rather than an elementary field that appears in an input Lagrangian. In particular, we emphasize the connection with the Barden-Cooper-Schrieffer theory of superconductivity. We identify the double-well Higgs potential not as a fundamental potential but as a mean-field effective Lagrangian with a dynamical Higgs boson being generated through a residual interaction that accompanies the mean-field Lagrangian. We discuss what we believe to be the key challenge raised by the discovery of the Higgs boson, namely determining whether it is elementary or composite, and through study of a conformal invariant field theory model as realized with critical scaling and anomalous dimensions, suggest that the width of the Higgs boson might serve as a suitable diagnostic for discriminating between an elementary Higgs boson and a composite one. We show that the contribution to the cosmological constant due to a composite Higgs boson is more tractable and under control than the contribution due to an elementary Higgs boson, and is potentially completely under control if there is an underlying conformal symmetry not just in a critical scaling matter sector, but equally in the gravity sector to which the matter sector couples.

    hep-phhep-thPPNP(2017)·66 citations
20. 20*

    Testing Hadronic Interactions at Ultrahigh Energies with Air Showers Measured by the Pierre Auger Observatory

    The Pierre Auger Collaboration: A. Aab🇩🇪 · P. Abreu🇵🇹 · M. Aglietta🇮🇹 · E.J. Ahn🇺🇸 · I. Al Samarai🇫🇷 · I.F.M. Albuquerque🇧🇷 · I. Allekotte🇦🇷 · J. Allen🇺🇸 · P. Allison🇺🇸 · A. Almela🇦🇷 · J. Alvarez Castillo🇲🇽 · J. Alvarez-Muñiz🇪🇸 and 425 other authors

    Ultrahigh energy cosmic ray air showers probe particle physics at energies beyond the reach of accelerators. Here we introduce a new method to test hadronic interaction models without relying on the absolute energy calibration, and apply it to events with primary energy 6-16 EeV (E_CM = 110-170 TeV), whose longitudinal development and lateral distribution were simultaneously measured by the Pierre Auger Observatory. The average hadronic shower is 1.33 +- 0.16 (1.61 +- 0.21) times larger than predicted using the leading LHC-tuned models EPOS-LHC (QGSJetII-04), with a corresponding excess of muons.

    ↳ hep-exastro-ph.HEhep-phPRL(2016)·301 citations
21. 21*

    Emergent Gravity from Vanishing Energy-Momentum Tensor

    Christopher D. Carone🇺🇸 · Joshua Erlich🇺🇸 · Diana Vaman🇺🇸

    A constraint of vanishing energy-momentum tensor is motivated by a variety of perspectives on quantum gravity. We demonstrate in a concrete example how this constraint leads to a metric-independent theory in which quantum gravity emerges as a nonperturbative artifact of regularization-scale physics. We analyze a scalar theory similar to the Dirac-Born-Infeld (DBI) theory with vanishing gauge fields, with the DBI Lagrangian modulated by a scalar potential. In the limit of a large number of scalars, we explicitly demonstrate the existence of a composite massless spin-2 graviton in the spectrum that couples to matter as in Einstein gravity. We comment on the cosmological constant problem and the generalization to theories with fermions and gauge fields.

    ↳ hep-thgr-qchep-phJHEP(2017)·17 citations
22. 22*

    Heavy quark production at an Electron-Ion Collider

    E. Chudakov🇺🇸 · D. Higinbotham🇺🇸 · Ch. Hyde🇺🇸 · S. Furletov🇺🇸 · Yu. Furletova🇺🇸 · D. Nguyen🇺🇸 · M. Stratmann🇩🇪 · M. Strikman🇺🇸 · C. Weiss🇺🇸

    An Electron-Ion Collider (EIC) with center-of-mass energies sqrt(s_{eN}) ~ 20-100 GeV and luminosity L ~ 10^{34} cm^{-2} s^{-1} would offer new opportunities to study heavy quark production in high-energy electron or photon scattering on protons and nuclei. We report about an R&D project exploring the feasibility of direct measurements of nuclear gluon densities at large x (gluonic EMC effect, antishadowing) using open charm production at EIC. We describe the charm production rates and angle-momentum distributions at large x and discuss methods of charm reconstruction using next-generation detector capabilities (pi/K identification, vertex reconstruction). The results can be used also for other physics applications of heavy quark production at EIC (fragmentation functions, jets, heavy quark propagation in nuclei).

    ↳ hep-exhep-phJ.Phys.Conf.Ser.(2016)·14 citations
23. 23*

    Prospects for Neutrino Spin Coherence in Supernovae

    James Y. Tian🇺🇸 · Amol V. Patwardhan🇺🇸 · George M. Fuller🇺🇸

    We present neutrino bulb model simulations of Majorana neutrino coherent spin transformation (i.e., neutrino-antineutrino transformation), coupled to neutrino flavor evolution, for conditions corresponding to the neutronization burst epoch of an Oxygen-Neon-Magnesium (O-Ne-Mg) core collapse supernova. Significant neutrino spin transformation in, for example, the neutronization burst, could alter the fluences of neutrinos and antineutrinos in a way which is potentially detectable for a Galactic core collapse supernova. Our calculations for the first time incorporate geometric dilution in the spin evolution of the neutrinos and combine two-flavor and three-flavor evolution with spin mixing physics. We find that significant spin transformations can occur, but only with a large neutrino luminosity and an electron fraction ($Y_e$) profile which facilitates adiabatic conditions for the spin-channel resonance. Using our adopted parameters of neutrino energy spectra, luminosity, density and $Y_e$ profiles, our calculations require an unrealistically large neutrino rest mass to sustain the spin transformation. It is an open question whether examining different density profiles or incorporating other sources of nonlinear feedback, such as $Y_e$ feedback, could mitigate this need. We find that spin transformations are not sensitive to the flavor structure of neutrinos, i.e., the spin transformations occur regardless of whether we simulate two- or three-flavor transformations. In the two-flavor case, spin transformations were insensitive to the choice of solar or atmospheric mass-squared splitting as well as the choice of the Majorana phase. Importantly, our three-flavor simulations, as well as our two-flavor simulations done with the atmospheric mass-squared splitting, show that the inclusion of spin degrees of freedom can significantly and qualitatively alter neutrino flavor evolution.

    ↳ astro-ph.HEhep-phPRD(2017)·29 citations
24. 24*

    The effect of hydrodynamical simulation inspired dark matter velocity profile on directional detection of dark matter

    Ranjan Laha🇺🇸

    Directional detection is an important way to detect dark matter. An input to these experiments is the dark matter velocity distribution. Recent hydrodynamical simulations have shown that the dark matter velocity distribution differs substantially from the Standard Halo Model. We study the impact of some of these updated velocity distribution in dark matter directional detection experiments. We calculate the ratio of events required to confirm the forward-backward asymmetry and the existence of the ring of maximum recoil rate using different dark matter velocity distributions for ${}^{19}$F and Xe targets. We show that with the use of updated dark matter velocity profiles, the forward-backward asymmetry and the ring of maximum recoil rate can be confirmed using a factor of $\sim$2 - 3 less events when compared to that using the Standard Halo Model.

    ↳ astro-ph.COastro-ph.GAhep-exhep-ph+1PRD(2018)·7 citations
25. 25*

    $\Lambda$ polarization in peripheral collisions at moderate relativistic energies

    Y.L. Xie🇳🇴 · M. Bleicher🇩🇪 · H. Stöcker🇩🇪 · D.J. Wang🇨🇳 · L.P. Csernai🇳🇴

    The polarization of $\Lambda$ hyperons from relativistic flow vorticity is studied in peripheral heavy ion reactions at FAIR and NICA energies, just above the threshold of the transition to the Quark-Gluon Plasma. Previous calculations at higher energies with larger initial angular momentum, predicted significant $\Lambda$ polarization based on the classical vorticity term in the polarization, while relativistic modifications decreased the polarization and changed its structure in the momentum space. At the lower energies studied here, we see the same effect namely that the relativistic modifications decrease the polarization arising from the initial shear flow vorticity.

    ↳ nucl-thhep-phPRC(2016)·59 citations
26. 26*

    Remembering Guido Altarelli

    Mario Greco🇮🇹

    In memory of Guido Altarelli I present my personal recollections of the early times and his major role played in the development of QCD.

    ↳ physics.hist-phhep-phFrascati Phys.Ser.(2017)·0 citations
27. 27*

    Equilibrium and non-equilibrium properties of the QGP in a magnetic field: a holographic approach

    Renato Critelli🇧🇷

    This manuscript reviews recent theoretical progress on the understanding of the quark gluon plasma in a magnetic field that I presented on the conference Hot Quarks 2016, held at South Padre Island, Texas, USA, 12-17 September 2016. It is shown that, using a holographic bottom-up Einstein-Maxwell-Dilaton model, one can have a good quantitative agreement with Lattice data for QCD equation of state and Polyakov loop with nonzero magnetic field. I also present results for the anisotropic shear viscosity ratio ${\eta }_{\parallel }/{\eta }_{\perp }$, with the conclusion that ${\eta }_{\parallel }<{\eta }_{\perp }$ for $B>0$.

    ↳ nucl-thhep-phhep-thJ.Phys.Conf.Ser.(2017)·2 citations
28. 28*

    New scenarios for hard-core interactions in a hadron resonance gas

    L. M. Satarov🇩🇪 · V. Vovchenko🇩🇪 · P. Alba🇩🇪 · M. I. Gorenstein🇺🇦 · H. Stoecker🇩🇪

    The equation of state of a baryon-symmetric hadronic matter with hard-sphere interactions is studied. It is assumed that mesons are point-like, but baryons and antibaryons have the same hard-core radius rB. Three possibilities are considered: 1) the baryon-baryon and antibaryon-baryon interactions are the same; 2) baryons do not interact with antibaryons; 3) the baryon-antibaryon and meson-(anti)baryon interactions are negligible. By choosing the parameter rB=0.3-0.6 fm, we calculate the nucleon to pion ratio as a function of temperature and perform the fit of hadron yields measured in central Pb+Pb collisions at the bombarding energy Ecm=2.76 TeV per nucleon pair. New nontrivial effects in the interacting hadron resonance gas at temperatures 150-200 MeV are found.

    ↳ nucl-thhep-phPRC(2017)·46 citations
29. 29*

    Simplification Rules for Birdtrack Operators

    Judith Alcock-Zeilinger🇿🇦 · Heribert Weigert🇿🇦

    This paper derives a set of easy-to-use tools designed to simplify calculations with birdtrack op- erators comprised of symmetrizers and antisymmetrizers. In particular, we present cancellation rules allowing one to shorten the birdtrack expressions of operators, and propagation rules identifying the circumstances under which it is possible to propagate symmetrizers past antisymmetrizers and vice versa. We exhibit the power of these simplification rules by means of a short example in which we apply the tools derived in this paper on a typical operator that can be encountered in the representation theory of SU(N) over the product space $V^{\otimes m}$ . These rules form the basis for the construction of compact Hermitian Young projection operators and their transition operators addressed in companion papers.

    ↳ math-phhep-phmath.MPJ.Math.Phys.(2017)·15 citations
30. 30*

    Transition Operators

    Judith Alcock-Zeilinger🇿🇦 · Heribert Weigert🇿🇦

    In this paper, we give a generic algorithm of the transition operators between Hermitian Young projection operators corresponding to equivalent irreducible representations of SU(N), using the compact expressions of Hermitian Young projection operators derived in a companion paper. We show that the Hermitian Young projection operators together with their transition operators constitute a fully orthogonal basis for the algebra of invariants of $V^{\otimes m}$ that exhibits a systematically simplified multiplication table. We discuss the full algebra of invariants over $V^{\otimes 3}$ and $V^{\otimes 4}$ as explicit examples. In our presentation we make use of various standard concepts such as Young projection operators, Clebsch-Gordan operators, and invariants (in birdtrack notation). We tie these perspectives together and use them to shed light on each other.

    ↳ math-phhep-phmath.MPJ.Math.Phys.(2017)·24 citations
31. 31*

    Impact of neutrino properties on the estimation of inflationary parameters from current and future observations

    Martina Gerbino🇸🇪 · Katherine Freese🇸🇪 · Sunny Vagnozzi🇸🇪 · Massimiliano Lattanzi🇮🇹 · Olga Mena🇪🇸 · Elena Giusarma🇺🇸 · Shirley Ho🇺🇸

    We study the impact of assumptions about neutrino properties on the estimation of inflationary parameters from cosmological data, with a specific focus on the allowed contours in the $n_s/r$ plane. We study the following neutrino properties: (i) the total neutrino mass $M_{\nu }={\sum }_i{m}_i$; (ii) the number of relativistic degrees of freedom $N_{eff}$; and (iii) the neutrino hierarchy: whereas previous literature assumed 3 degenerate neutrino masses or two massless neutrino species (that do not match neutrino oscillation data), we study the cases of normal and inverted hierarchy. Our basic result is that these three neutrino properties induce $<1\sigma$ shift of the probability contours in the $n_s/r$ plane with both current or upcoming data. We find that the choice of neutrino hierarchy has a negligible impact. However, the minimal cutoff on the total neutrino mass $M_{\nu ,min}=0$ that accompanies previous works using the degenerate hierarchy does introduce biases in the $n_s/r$ plane and should be replaced by $M_{\nu ,min}=0.059$ eV as required by oscillation data. Using current CMB data from Planck and Bicep/Keck, marginalizing over $M_{\nu }$ and over $r$ can lead to a shift in the mean value of $n_s$ of $\sim 0.3\sigma$ towards lower values. However, once BAO measurements are included, the standard contours in the $n_s/r$ plane are basically reproduced. Larger shifts of the contours in the $n_s/r$ plane (up to 0.8$\sigma$) arise for nonstandard values of $N_{eff}$. We also provide forecasts for the future CMB experiments COrE and Stage-IV and show that the incomplete knowledge of neutrino properties, taken into account by a marginalization over $M_{\nu }$, could induce a shift of $\sim 0.4\sigma$ towards lower values in the determination of $n_s$ (or a $\sim 0.8\sigma$ shift if one marginalizes over $N_{eff}$). Comparison to specific inflationary models is shown.

    ↳ astro-ph.COhep-phPRD(2017)·100 citations
32. 32*

    An Axion-induced SM/MSSM Higgs Landscape and the Weak Gravity Conjecture

    Alvaro Herraez🇪🇸 · Luis E. Ibanez🇪🇸

    We construct models in which the SM Higgs mass scans in a landscape. This is achieved by coupling the SM to a monodromy axion field through Minkowski 3-forms. The Higgs mass scans with steps given by delta(m_H^2)= eta mu f, where mu and f are the axion mass and periodicity respectively, and eta measures the coupling of the Higgs to the associated 3-form. The observed Higgs mass scale could then be selected on anthropic grounds. The monodromy axion may have a mass mu in a very wide range depending on the value of eta, and the axion periodity f. For eta=1 and f = 10^10 GeV, one has 10^{-3}eV < mu < 10^3 eV, but ultralight axions with e.g. mu = 10^{-17} eV are also possible. In a different realization we consider landscape models coupled to the MSSM. In the context of SUSY, 4-forms appear as being part of the auxiliary fields of SUSY multiplets. The scanning in the 4-forms thus translate into a landscape of vevs for the N=1 auxiliary fields and hence as a landscape for the soft terms. This could provide a rationale for the MSSM fine-tuning suggested by LHC data. In all these models there are 3-forms coupling to membranes which induce transitions between different vacua through bubble nucleation. The Weak Gravity Conjecture (WGC) set limits on the tension of these membranes and implies new physics thresholds well below the Planck scale. More generaly, we argue that in the case of string SUSY vacua in which the Goldstino multiplet contains a monodromy axion the WGC suggests a lower bound on the SUSY breaking scale m_{3/2} > M_s^2/M_p.

    ↳ hep-thhep-phJHEP(2017)·38 citations
33. 33*

    Preheating after multifield inflation with nonminimal couplings, II: Resonance Structure

    Matthew P. DeCross🇺🇸 · David I. Kaiser🇺🇸 · Anirudh Prabhu🇺🇸 · Chanda Prescod-Weinstein🇺🇸 · Evangelos I. Sfakianakis🇺🇸

    This is the second in a series of papers on preheating in inflationary models comprised of multiple scalar fields coupled nonminimally to gravity. In this paper, we work in the rigid-spacetime approximation and consider field trajectories within the single-field attractor, which is a generic feature of these models. We construct the Floquet charts to find regions of parameter space in which particle production is efficient for both the adiabatic and isocurvature modes, and analyze the resonance structure using analytic and semi-analytic techniques. Particle production in the adiabatic direction is characterized by the existence of an asymptotic scaling solution at large values of the nonminimal couplings, ${\xi }_I\gg 1$, in which the dominant instability band arises in the long-wavelength limit, for comoving wavenumbers $k\to 0$. However, the large-${\xi }_I$ regime is not reached until ${\xi }_I\ge \mathcal{O}(100)$. In the intermediate regime, with ${\xi }_I\sim \mathcal{O}(1-10)$, the resonance structure depends strongly on wavenumber and couplings. The resonance structure for isocurvature perturbations is distinct and more complicated than its adiabatic counterpart. An intermediate regime, for ${\xi }_I\sim \mathcal{O}(1-10)$, is again evident. For large values of ${\xi }_I$, the Floquet chart consists of densely spaced, nearly parallel instability bands, suggesting a very efficient preheating behavior. The increased efficiency arises from features of the nontrivial field-space manifold in the Einstein frame, which itself arises from the fields' nonminimal couplings in the Jordan frame, and has no analogue in models with minimal couplings. Quantitatively, the approach to the large-${\xi }_I$ asymptotic solution for isocurvature modes is slower than in the case of the adiabatic modes.

    ↳ astro-ph.COhep-phhep-thPRD(2018)·88 citations
34. 34*

    Compact Hermitian Young Projection Operators

    Judith Alcock-Zeilinger🇿🇦 · Heribert Weigert🇿🇦

    In this paper, we describe a compact and practical algorithm to construct Hermitian Young projection operators for irreducible representations of the special unitary group SU(N), and discuss why ordinary Young projection operators are unsuitable for physics applications. The proof of this construction algorithm uses the iterative method described by Keppeler and Sjödahl. We further show that Hermitian Young projection operators share desirable properties with Young tableaux, namely a nested hierarchy when "adding a particle". We end by exhibiting the enormous advantage of the Hermitian Young projection operators constructed in this paper over those given by Keppeler and Sjödahl.

    ↳ math-phhep-phmath.MPJ.Math.Phys.(2017)·26 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.