Mon·Jul 20, 2015Monday·July 20, 2015

1. 01*

   Techniques for the treatment of IR divergences in decay processes at NLO and application to the top-quark decay

   Lorenzo Basso🇫🇷 · Stefan Dittmaier🇩🇪 · Alexander Huss🇨🇭 · Luisa Oggero🇩🇪

   We present the extension of two general algorithms for the treatment of infrared singularities arising in electroweak corrections to decay processes at next-to-leading order: the dipole subtraction formalism and the one-cutoff slicing method. The former is extended to the case of decay kinematics which has not been considered in the literature so far. The latter is generalized to production and decay processes with more than two charged particles, where new "surface" terms arise. Arbitrary patterns of massive and massless external particles are considered, including the treatment of infrared singularities in dimensional or mass regularization. As an application of the two techniques we present the calculation of the next-to-leading-order QCD and electroweak corrections to the top-quark decay width including all off-shell and decay effects of intermediate W bosons. The result, e.g., represents a building block of a future calculation of NLO electroweak effects to off-shell top-quark pair (WWbb) production. Moreover, this calculation can serve as the first step towards an event generator for top-quark decays at next-to-leading order accuracy, which can be used to attach top-quark decays to complicated many-particle top-quark processes, such as for tt+H or tt+jets.

   hep-phEPJC(2016)·50 citations
2. 02*

   Elliptic flow difference of charged pions in heavy-ion collisions

   Yoshitaka Hatta🇯🇵 · Akihiko Monnai🇺🇸 · Bo-Wen Xiao🇨🇳

   Recently, the STAR collaboration at RHIC has presented experimental evidence for the correlation between the elliptic flow difference of charged pions and charge asymmetry as a possible signal of the chiral magnetic wave. We demonstrate that the STAR results can be understood within the standard viscous hydrodynamics.

   hep-phnucl-exnucl-thNPA(2016)·43 citations
3. 03*

   Is pentaquark doublet a hadronic molecule?

   A. Mironov🇷🇺 · A. Morozov🇷🇺

   A recently announced discovery by LHCb of a doublet of overlapping pentaquark resonances poses a question of what can be the origin of this doublet structure. We attract attention to the fact that such degeneracy could naturally arise if constituent "baryon" and "meson" were in the colored rather than colorless states. This is an appealing possibility, also because in such a case the pentaquark state would be no less "elementary" than the other hadrons, and would provide a chance for essentially new non-Abelian chemistry.

   hep-phhep-thJETP Lett.(2015)·96 citations
4. 04*

   Evaluating the double parton scattering contribution to Mueller-Navelet jets production at the LHC

   B. Ducloué🇫🇮 · L. Szymanowski🇵🇱 · S. Wallon🇫🇷

   We propose a model to study the importance of double parton scattering (DPS) in Mueller-Navelet jets production at the LHC which is consistent with the BFKL framework used to compute the single parton scattering contribution to this process. We study this model in kinematics corresponding to existing and possible future measurements at the LHC and estimate the importance of this DPS contribution on relevant observables for this process, namely the cross section and the azimuthal correlation of the jets.

   hep-phhep-exPRD(2015)·62 citations
5. 05*

   CP violation from spin-1 resonances in a left-right dynamical Higgs context

   Kunming Ruan🇨🇳 · Jing Shu🇨🇳 · Juan Yepes🇨🇳

   New physics field content in the nature, more specifically, from spin-1 resonances sourced by the extension of the SM local gauge symmetry to the larger local group $SU(2{)}_L\otimes SU(2{)}_R\otimes U(1{)}_{B-L}$, may induce CP-violation signalling NP effects from higher energy regimes. In this work we completely list and study all the CP-violating operators up to the $p^4$-order in the Lagrangian expansion, for a non-linear left-right electroweak chiral context and coupled to a light dynamical Higgs. Heavy right handed fields can be integrated out from the physical spectrum, inducing thus a physical impact in the effective gauge couplings, fermionic electric dipole moment, and CP-violation in the decay $h\to Z{Z}^{\ast }\to 4l$ that are briefly analysed. The final relevant set of effective operators have also been identified at low energies.

   hep-phCommun.Theor.Phys.(2016)·12 citations
6. 06*

   Critical versus spurious fluctuations in the search for the QCD critical point

   Maurício Hippert🇧🇷 · Eduardo S. Fraga🇧🇷 · Edivaldo M. Santos🇧🇷

   The neighborhood of the QCD chiral critical point is characterized by intense fluctuations of the chiral field which could, in principle, generate pronounced experimental signatures. However, experimental uncertainties which are inherent to heavy ion collisions, as well as the modest size and duration of the formed plasma, will severely attenuate these signatures. Using Monte Carlo techniques, we study second-order event-by-event moments of pions as a prototype for signatures of the chiral critical point based on the enhancement of the correlation length and event-by-event analysis. We test their viability against some realistic ingredients, similar to the ones found in the RHIC Beam Energy Scan program.

   hep-phnucl-thPRD(2016)·18 citations
7. 07*

   Revolving D-branes and Spontaneous Gauge Symmetry Breaking

   Satoshi Iso🇯🇵 · Noriaki Kitazawa🇯🇵

   We propose a new mechanism of spontaneous gauge symmetry breaking in the world-volume theory of revolving D-branes around a fixed point of orbifolds. In this paper, we consider a simple model of the T6/Z3 orbifold on which we put D3-branes, D7-branes and their anti-branes. The configuration breaks supersymmetry, but the R-R tadpole cancellation conditions are satisfied. A set of three D3-branes at an orbifold fixed point can separate from the point, but when they move perpendicular to the anti-D7-branes put on the fixed point, they are forced to be pulled back due to an attractive interaction between the D3 and anti-D7 branes. In order to stabilize the separation of the D3-branes at nonzero distance, we consider revolution of the D3-branes around the fixed point. Then the gauge symmetry on D3-branes is spontaneously broken, and the rank of the gauge group is reduced. The distance can be set at our will by appropriately choosing the angular momentum of the revolving D3-branes, which should be determined by the initial condition of the cosmological evolution of D-brane configurations. The distance corresponds to the vacuum expectation values of brane moduli fields in the world-volume theory and, if it is written as M/Ms^2 in terms of the string scale Ms, the scale of gauge symmetry breaking is given by M. Angular momentum conservation of revolving D3-branes assures the stability of the scale M against Ms.

   hep-phastro-ph.COhep-thPTEP(2015)·8 citations
8. 08*

   Evidence for the decay $\psi (3770)\to K^{+}{K}^{-}$

   V. P. Druzhinin🇷🇺

   Existing data on the $e^{+}{e}^{-}\to K^{+}{K}^{-}$ cross section at the center-of-mass energy above 2.6 GeV are fitted with a sum of $\psi (3770)$ resonant and continuum contributions. Two solutions for the resonance production cross section are found with a significance of 3.2$\sigma$. Data on the $e^{+}{e}^{-}\to K_S{K}_L$ cross section are used to resolve the ambiguity and for further constraining the values of the $e^{+}{e}^{-}\to \psi (3770)\to K^{+}{K}^{-}$ cross section and the interference phase. They are found to be ${\sigma }_{\psi (3770)}=0.073_{-0.044}^{+0.061}$ pb and $\varphi =(309_{-35}^{+17}{)}^{\circ }$, respectively. The same fitting procedure for the $\psi (4160)$ resonance leads to the upper limit on the $e^{+}{e}^{-}\to \psi (4160)\to K^{+}{K}^{-}$ cross section ${\sigma }_{\psi (4160)}<0.062$ pb at 90\% confidence level.

   hep-phhep-exPRD(2015)·2 citations
9. 09*

   Derivation of second-order relativistic hydrodynamics for reactive multi-component systems

   Yuta Kikuchi🇯🇵 · Kyosuke Tsumura🇯🇵 · Teiji Kunihiro🇯🇵

   We derive the second-order hydrodynamic equation for reactive multi-component systems from the relativistic Boltzmann equation. In the reactive system, particles can change their species under the restriction of the imposed conservation laws during the collision process. Our derivation is based on the renormalization group (RG) method, in which the Boltzmann equation is solved in an organized perturbation method as faithfully as possible and possible secular terms are resummed away by a suitable setting of the initial value of the distribution function. The microscopic formulae of the relaxation times and the lengths are explicitly given as well as those of the transport coefficients for the reactive multi-component system. The resultant hydrodynamic equation with these formulae has nice properties that it satisfies the positivity of the entropy production rate and the Onsager's reciprocal theorem, which ensure the validity of our derivation.

   hep-phnucl-thphysics.flu-dynPRC(2015)·21 citations
10. 10*

    Self-interacting dark matter and cosmology of a light scalar mediator

    Kimmo Kainulainen🇫🇮 · Kimmo Tuominen🇫🇮 · Ville Vaskonen🇫🇮

    We consider a fermionic dark matter candidate interacting via a scalar mediator coupled with the Standard Model through a Higgs portal. We consider general setting including both scalar and pseudoscalar interactions between the scalar and fermion, and illustrate the relevant features for dark matter abundance, direct search limits and collider constraints. The case where dark matter has a self-interaction strength $⟨{\sigma }_V⟩/m_{\psi }\sim 0.1-1{\mathrm{cm}}^2/\mathrm{g}$ is strongly constrained, in particular by the Big Bang Nucleosynthesis. We show that these constraints can be alleviated by introducing a new light sterile neutrino $N$. The allowed region for the extended model consists of a triangle at $10(\sin \theta {)}^{-2/5}\mathrm{MeV}\lesssim m_N\lesssim 1\mathrm{GeV}$.

    hep-phastro-ph.COPRD(2016)·73 citations
11. 11*

    How to reveal the exotic nature of the P_c(4450)

    Feng-Kun Guo🇩🇪 · Ulf-G. Meißner🇩🇪 · Wei Wang🇨🇳 · Zhi Yang🇩🇪

    The LHCb Collaboration announced two pentaquark-like structures in the $J/\psi p$ invariant mass distribution. We show that the current information on the narrow structure at 4.45 GeV is compatible with kinematical effects of the rescattering from ${\chi }_{c1}p$ to $J/\psi p$: First, it is located exactly at the ${\chi }_{c1}p$ threshold. Second, the mass of the four-star well-established $\Lambda (1890)$ is such that a leading Landau singularity from a triangle diagram can coincidentally appear at the ${\chi }_{c1}p$ threshold, and third, there is a narrow structure at the ${\chi }_{c1}p$ threshold but not at the ${\chi }_{c0}p$ and ${\chi }_{c2}p$ thresholds. In order to check whether that structure corresponds to a real exotic resonance, one has to measure the process ${\Lambda }_b^0\to K^{-}{\chi }_{c1}p$. If the $P_c(4450)$ structure exists in the ${\chi }_{c1}p$ invariant mass distribution as well, then the structure cannot be just a kinematical effect but is a real resonance, otherwise, one cannot conclude the $P_c(4450)$ to be another exotic hadron. In addition, it is also worthwhile to measure the decay ${\rm Y}(1S)\to J/\psi p\bar{p}$: a narrow structure at 4.45 GeV but not at the ${\chi }_{c0}p$ and ${\chi }_{c2}p$ thresholds would exclude the possibility of a pure kinematical effect.

    hep-phhep-exhep-latnucl-thPRD(2015)·357 citations
12. 12*

    Shocking Signals of Dark Matter Annihilation

    Jonathan H. Davis🇫🇷 · Joseph Silk🇫🇷 · Celine Boehm🇬🇧 · Kumiko Kotera🇫🇷 · Colin Norman🇺🇸

    We examine whether charged particles injected by self-annihilating Dark Matter into regions undergoing Diffuse Shock Acceleration (DSA) can be accelerated to high energies. We consider three astrophysical sites where shock acceleration is supposed to occur, namely the Galactic Centre, galaxy clusters and Active Galactic Nuclei (AGN). For the Milky Way, we find that the acceleration of cosmic rays injected by dark matter could lead to a bump in the cosmic ray spectrum provided that the product of the efficiency of the acceleration mechanism and the concentration of DM particles is high enough. Among the various acceleration sources that we consider (namely supernova remnants (SNRs), Fermi bubbles and AGN jets), we find that the Fermi bubbles are a potentially more efficient accelerator than SNRs. However both could in principle accelerate electrons and protons injected by dark matter to very high energies. At the extragalactic level, the acceleration of dark matter annihilation products could be responsible for enhanced radio emission from colliding clusters and prediction of an increase of the anti-deuteron flux generated near AGNs.

    hep-phastro-ph.HEPRD(2016)·2 citations
13. 13*

    The New Pentaquarks in the Diquark Model

    L. Maiani🇮🇹 · A.D. Polosa🇮🇹 · V. Riquer🇮🇹

    Pentaquark baryons are a natural expectation of an extended picture of hadrons where quarks and diquarks are the fundamental units. The parity/mass pattern observed, when compared to that of exotic mesons, appears as the footprint of a compact five-quark structure. What has been learned from the X,Y,Z phenomenology informs about the newly found pentaquark structure and suggests further experimental tests and directions to be explored.

    hep-phPLB(2015)·316 citations
14. 14*

    Family Gauge Boson Production at the LHC

    Yoshio Koide🇯🇵 · Masato Yamanaka🇯🇵 · Hiroshi Yokoya🇰🇷

    Family gauge boson production at the LHC is investigated according to a $U(3)$ family gauge model with twisted family number assignment. In the model we study, a family gauge boson with the lowest mass, $A_1^1$, interacts only with the first generation leptons and the third generation quarks. (The family numbers are assigned, for example, as $(e_1,e_2,e_3)=(e^{-},{\mu }^{-},{\tau }^{-})$ and $(d_1,d_2,d_3)=(b,d,s)$[or $(d_1,d_2,d_3)=(b,s,d)$]). In the model, the family gauge coupling constant is fixed by relating to the electroweak gauge coupling constant. Thus measurements of production cross sections and branching ratios of $A_1^1$ clearly confirm or rule out the model. We calculate the cross sections of inclusive $A_1^1$ production and $b\bar{b}(t\bar{t})$ associated $A_1^1$ production at $\sqrt{s}=14\text{TeV}$ and $100\text{TeV}$. With the dielectron production cross section, we discuss the determination of diagonalizing matrix of quark mass matrix, $U_u$ and $U_d$, respectively.

    hep-phPLB(2015)·2 citations
15. 15*

    Classical scale invariance in the inert doublet model

    Alexis D. Plascencia🇬🇧

    The inert doublet model (IDM) is a minimal extension of the Standard Model (SM) that can account for the dark matter in the universe. Naturalness arguments motivate us to study whether the model can be embedded into a theory with dynamically generated scales. In this work we study a classically scale invariant version of the IDM with a minimal hidden sector, which has a $U(1{)}_{\text{CW}}$ gauge symmetry and a complex scalar $\Phi$. The mass scale is generated in the hidden sector via the Coleman-Weinberg (CW) mechanism and communicated to the two Higgs doublets via portal couplings. Since the CW scalar remains light, acquires a vacuum expectation value and mixes with the SM Higgs boson, the phenomenology of this construction can be modified with respect to the traditional IDM. We analyze the impact of adding this CW scalar and the $Z^{\prime }$ gauge boson on the calculation of the dark matter relic density and on the spin-independent nucleon cross section for direct detection experiments. Finally, by studying the RG equations we find regions in parameter space which remain valid all the way up to the Planck scale.

    hep-phJHEP(2015)·56 citations
16. 16*

    Tetraquarks from the Bethe-Salpeter equation

    Gernot Eichmann🇩🇪 · Christian S. Fischer🇩🇪 · Walter Heupel🇩🇪

    We present a numerical solution of the four-quark Bethe-Salpeter equation for a scalar tetraquark. We find that the four-body equation dynamically generates pseudoscalar poles in the Bethe-Salpeter amplitude. The sensitivity to the pion poles leads to a light isoscalar tetraquark mass M ~ 400 MeV, which is comparable to that of the sigma/f0(500). The masses of its multiplet partners kappa and a0/f0 follow a similar pattern, thereby providing support for the tetraquark interpretation of the light scalar nonet.

    hep-phnucl-thActa Phys.Polon.Supp.(2015)·7 citations
17. 17*

    Survey of Higgs interpretations of the diboson excesses

    Yuji Omura🇯🇵 · Kazuhiro Tobe🇯🇵 · Koji Tsumura🇯🇵

    We investigate diboson signals in the Standard Model (SM) with an extended Higgs sector, motivated by the excesses in the diboson channels at the LHC. We begin with the unitarity sum-rules of the weak gauge boson scattering assuming the Higgs sector is extended. According to the sum-rules, we discuss the Higgs interpretations of the diboson signals and the consistency with the ATLAS diboson anomaly and other experimental constraints. As a concrete example, we propose a two-Higgs-doublet model where the Yukawa coupling of an extra CP-even scalar with up-type quark is relatively large. The diboson (WW and ZZ) signals can be explained by 2 TeV CP-even Higgs boson, while the partners, the CP-odd and the charged Higgs bosons in the extra doublet, are severely constrained by both the LHC direct search and the indirect search via flavor observables. Especially, in order to avoid the diboson resonance search in the Vh channel, further extensions of the model are required. The diboson excess is correlated with the SM Higgs signals in our framework, so that the precise measurement of the SM Higgs boson is also important to test the Higgs interpretation.

    hep-phhep-exPRD(2015)·35 citations
18. 18*

    Flavour, Electroweak Symmetry Breaking and Dark Matter: state of the art and future prospects

    Giulia Ricciardi🇮🇹 · Alexandre Arbey🇫🇷 · Enrico Bertuzzo🇪🇸 · Adrian Carmona🇨🇭 · Radovan Dermisek🇺🇸 · Tobias Huber🇩🇪 · Tobias Hurth🇩🇪 · Yuval Grossman🇺🇸 · Joern Kersten🇳🇴 · Enrico Lunghi🇺🇸 · Farvah Mahmoudi🇫🇷 · Antonio Masiero🇮🇹 and 3 other authors

    With the discovery of the Higgs boson the Standard Model has become a complete and comprehensive theory, which has been verified with unparalleled precision and in principle might be valid at all scales. However, several reasons remain why we firmly believe that there should be physics beyond the Standard Model. Experiments such as the LHC, new $B$ factories, and earth- and space-based astro-particle experiments provide us with unique opportunities to discover a coherent framework for many of the long-standing puzzles of our field. Here we explore several significant interconnections between the physics of the Higgs boson, the physics of flavour, and the experimental clues we have about dark matter.

    hep-phgr-qchep-exhep-thEur.Phys.J.Plus(2015)·4 citations
19. 19*

    Isospin splitting of nucleon effective mass from giant resonances in ${}^{208}$Pb

    Zhen Zhang🇨🇳 · Lie-Wen Chen🇨🇳

    Based on mean field calculations with Skyrme interactions, we extract a constraint on the isovector effective mass in nuclear matter at saturation density ${\rho }_0$, i.e., $m_v^{\ast }({\rho }_0)=(0.77\pm 0.03)m$ by combining the experimental data of the centroid energy of the isovector giant dipole resonance (IVGDR) and the electric dipole polarizability ${\alpha }_{\mathrm{D}}$ in ${}^{208}$Pb. Meanwhile, the isoscalar effective mass at ${\rho }_0$ is determined to be $m_s^{\ast }({\rho }_0)=(0.91\pm 0.05)m$ by analyzing the measured excitation energy of the isoscalar giant quadrupole resonance (ISGQR) in ${}^{208}$Pb. From the constrained $m_s^{\ast }({\rho }_0)$ and $m_v^{\ast }({\rho }_0)$, we obtain the isospin splitting of nucleon effective mass in asymmetric nuclear matter of isospin asymmetry $\delta$ at ${\rho }_0$ as $[m_n^{\ast }({\rho }_0,\delta )-m_p^{\ast }({\rho }_0,\delta )]/m=\Delta m_1^{\ast }({\rho }_0)\delta +O({\delta }^3)$ with the linear isospin splitting coefficient $\Delta m_1^{\ast }({\rho }_0)=0.33\pm 0.16$. We notice that using the recently corrected data on the ${\alpha }_{\mathrm{D}}$ in ${}^{208}$Pb with the contribution of the quasideuteron effect subtracted slightly enhances the isovector effective mass to $m_v^{\ast }({\rho }_0)=(0.80\pm 0.03)m$ and reduces the linear isospin splitting coefficient to $\Delta m_1^{\ast }({\rho }_0)=0.27\pm 0.15$. Furthermore, the constraints on $m_v^{\ast }(\rho )$, $m_s^{\ast }(\rho )$ and $\Delta m_1^{\ast }(\rho )$ at other densities are obtained from the similar analyses and we find that the $\Delta m_1^{\ast }(\rho )$ increases with the density.

    ↳ nucl-thastro-ph.SRhep-phnucl-exPRC(2016)·51 citations
20. 20*

    Helical Phase Inflation via Non-Geometric Flux Compactifications: from Natural to Starobinsky-like Inflation

    Tianjun Li🇨🇳 · Zhijin Li🇺🇸 · Dimitri V. Nanopoulos🇺🇸

    We show that a new class of helical phase inflation models can be simply realized in minimal supergravity, wherein the inflaton is the phase component of a complex field and its potential admits a deformed helicoid structure. We find a new unique complex-valued index $\chi$ that characterizes almost the entire region of the $n_s-r$ plane favored by new Planck observations. Continuously varying the index $\chi$, predictions interpolate from quadratic/natural inflation parameterized by a phase/axion decay constant to Starobinsky-like inflation parameterized by the $\alpha$-parameter. We demonstrate that the simple supergravity construction realizing Starobinsky-like inflation can be obtained from a more microscopic model by integrating out heavy fields, and that the flat phase direction for slow-roll inflation is protected by a mildly broken global $U(1)$ symmetry. %, which is mildly broken at the inflation energy scale. We study the geometrical origin of the index $\chi$, and find that it corresponds to a linear constraint relating \kah moduli. We argue that such a linear constraint is a natural result of moduli stabilization in Type \MyRoman{2} orientifold compactifications on Calabi-Yau threefolds with geometric and non-geometric fluxes. Possible choices for the index $\chi$ are discrete points on the complex plane that relate to the distribution of supersymmetric Minkowski vacua on moduli space. More precise observations of the inflationary epoch in the future may provide a better estimation of the index $\chi$. Since $\chi$ is determined by the fluxes and vacuum expectation values of complex structure moduli, such observations would characterize the geometry of the internal space as well.

    ↳ hep-thastro-ph.COhep-phJHEP(2015)·28 citations
21. 21*

    Decay constants in soft wall AdS/QCD revisited

    Nelson R. F. Braga🇧🇷 · M. A. Martin Contreras🇨🇴 · Saulo Diles🇧🇷

    Phenomenological AdS/QCD models, like hard wall and soft wall, provide hadronic mass spectra in reasonable consistency with experimental and (or) lattice results. These simple models are inspired in the AdS/CFT correspondence and assume that gauge/ gravity duality holds in a scenario where conformal invariance is broken through the introduction of an energy scale. Another important property of hadrons: the decay constant, can also be obtained from these models. However, a consistent formulation of an AdS/QCD model that reproduces the observed behavior of decay constants of vector meson excited states is still lacking. In particular: for radially excited states of heavy vector mesons, the experimental data lead to decay constants that decrease with the radial excitation level. We show here that a modified framework of soft wall AdS/QCD involving an additional dimensionfull parameter, associated with an ultraviolet energy scale, provides decay constants decreasing with radial excitation level. In this version of the soft wall model the two point function of gauge theory operators is calculated at a finite position of the anti-de Sitter space radial coordinate.

    ↳ hep-thhep-phPLB(2016)·57 citations
22. 22*

    Dark Matter Velocity Spectroscopy

    Eric G. Speckhard🇺🇸 · Kenny C. Y. Ng🇺🇸 · John F. Beacom🇺🇸 · Ranjan Laha🇺🇸

    Dark matter decays or annihilations that produce line-like spectra may be smoking-gun signals. However, even such distinctive signatures can be mimicked by astrophysical or instrumental causes. We show that velocity spectroscopy-the measurement of energy shifts induced by relative motion of source and observer-can separate these three causes with minimal theoretical uncertainties. The principal obstacle has been energy resolution, but upcoming experiments will reach the required 0.1% level. As an example, we show that the imminent Astro-H mission can use Milky Way observations to separate possible causes of the 3.5-keV line. We discuss other applications.

    ↳ astro-ph.COastro-ph.HEhep-exhep-ph+1PRL(2016)·44 citations
23. 23*

    Fluctuations in slope parameter in event-by-event hydrodynamics and momentum anisotropy in heavy ion collisions

    A. K. Chaudhuri🇮🇳

    In event by event hydrodynamic model, we have simulated 30-40\% Au+Au collisions at RHIC and computed the slope parameter from the invariant pion distribution. In each event, the slope parameter fluctuates azimuthally. Fourier expansion coefficients $T_n$ for the slope parameter and the Fourier expansion coefficients $v_n$ for the azimuthal distribution $\frac{dN}{d\varphi }$ are found to be strongly correlated. Strong correlation between the two expansion coefficients suggests that in addition to azimuthal distribution, fluctuations in the slope parameter of the invariant distribution can as well be used to study the final state momentum anisotropy in relativistic energy heavy ion collisions. If measured experimentally, they can serve as additional constraint for hydrodynamical modeling.

    ↳ nucl-thhep-ph1 citation
24. 24*

    Nucleon and pion structure with lattice QCD simulations at physical value of the pion mass

    A. Abdel-Rehim (Cyprus Inst.)🇨🇾 · C. Alexandrou (Cyprus Inst. & Univ. of Cyprus)🇨🇾 · M. Constantinou (Cyprus Inst. & Univ. of Cyprus)🇨🇾 · P. Dimopoulos (Fermi Center & Rome Tor Vergata)🇮🇹 · R. Frezzotti (INFN & Rome Tor Vergata)🇮🇹 · K. Hadjiyiannakou (Univ. of Cyprus & Cyprus Inst.)🇨🇾 · K. Jansen (DESY)🇩🇪 · Ch. Kallidonis (Cyprus Inst.)🇨🇾 · B. Kostrzewa (Humboldt Univ. & DESY)🇩🇪 · G. Koutsou (Cyprus Inst.)🇨🇾 · M. Mangin-Brinet (Grenoble)🇫🇷 · M. Oehm (Bonn Univ.)🇩🇪 and 3 other authors

    We present results on the nucleon scalar, axial and tensor charges as well as on the momentum fraction, and the helicity and transversity moments. The pion momentum fraction is also presented. The computation of these key observables is carried out using lattice QCD simulations at a physical value of the pion mass. The evaluation is based on gauge configurations generated with two degenerate sea quarks of twisted mass fermions with a clover term. We investigate excited states contributions with the nucleon quantum numbers by analyzing three sink-source time separations. We find that, for the scalar charge, excited states contribute significantly and to a less degree to the nucleon momentum fraction and helicity moment. Our analysis yields a value for the nucleon axial charge agrees with the experimental value and we predict a value of 1.027(62) in the $\overline{\text{MS}}$ scheme at 2 GeV for the isovector nucleon tensor charge directly at the physical point. The pion momentum fraction is found to be $⟨x{⟩}_{u-d}^{{\pi }^{\pm }}=0.214(15){(}_{-9}^{+12})$ in the $\overline{\mathrm{MS}}$ at 2 GeV.

    ↳ hep-lathep-phnucl-exnucl-thPRD(2015)·175 citations
25. 25*

    Using Drell-Yan $A_{FB}$ to constrain PDFs

    A. Bodek🇺🇸 · J. Y. Han🇺🇸 · A. Khukhunaishvili🇺🇸 · W. Sakumoto🇺🇸

    We show that measurements of the forward-backward charge asymmetry ($A_{FB}(M,y)$) of Drell-Yan dilepton events produced at hadron colliders provide a new powerful tool to constrain Parton Distribution Functions (PDFs). PDF uncertainties are the dominant source of systematic error in precision measurements at hadron colliders (e.g. ${\chi }^2$ values of fits to extract ${\sin }^2{\theta }_{eff}^{lept}(M_Z)$ from $A_{FB}(M,y)$ with different PDF replicas can be used to place additional constraints on PDFs.In turn, using these constrained PDFs significantly reduces the PDF errors in precision measurements of electroweak parameters. The measurement of the on-shell ${\sin }^2{\theta }_W=1-M_W^2/M_Z^2$ is equivalent to an indirect measurement of the W mass. The errors in this indirect measurement of the W mass are competitive with direct measurements. For example, with 200 fb${}^{-1}$ at 13 TeV, the expected error in the indirect measurement of the W mass is $\pm$9 MeV.

    ↳ hep-exhep-phPoS(2015)·0 citations
26. 26*

    Primordial perturbations from dilaton-induced gauge fields

    Kiwoon Choi🇰🇷 · Ki-Young Choi🇰🇷 · Hyungjin Kim🇰🇷 · Chang Sub Shin🇺🇸

    We study the primordial scalar and tensor perturbations in inflation scenario involving a spectator dilaton field. In our setup, the rolling spectator dilaton causes a tachyonic instability of gauge fields, leading to a copious production of gauge fields in the superhorizon regime, which generates additional scalar and tensor perturbations through gravitational interactions. Our prime concern is the possibility to enhance the tensor-to-scalar ratio $r$ relative to the standard result, while satisfying the observational constraints. To this end, we allow the dilaton field to be stabilized before the end of inflation, but after the CMB scales exit the horizon. We show that for the inflaton slow roll parameter $ϵ\gtrsim 10^{-3}$, the tensor-to-scalar ratio in our setup can be enhanced only by a factor of $\mathcal{O}(1)$ compared to the standard result. On the other hand, for smaller $ϵ$ corresponding to a lower inflation energy scale, a much bigger enhancement can be achieved, so that our setup can give rise to an observably large $r\gtrsim 10^{-2}$ even when $ϵ\ll 10^{-3}$. The tensor perturbation sourced by the spectator dilaton can have a strong scale dependence, and is generically red-tilted. We also discuss a specific model to realize our scenario, and identify the parameter region giving an observably large $r$ for relatively low inflation energy scales.

    ↳ astro-ph.COhep-phhep-thJCAP(2015)·22 citations
27. 27*

    Chiral Magnetic Effect in Protoneutron Stars and Magnetic Field Spectral Evolution

    Günter Sigl🇩🇪 · Natacha Leite🇩🇪

    We investigate the evolution of the chiral magnetic instability in a protoneutron star and compute the resulting magnetic power and helicity spectra. The instability may act during the early cooling phase of the hot protoneutron star after supernova core collapse, where it can contribute to the buildup of magnetic fields of strength up to the order of $10^{14}$ G. The maximal field strengths generated by this instability, however, depend considerably on the temperature of the protoneutron star, on density fluctuations and turbulence spectrum of the medium. At the end of the hot cooling phase the magnetic field tends to be concentrated around the submillimeter to cm scale, where it is subject to slow resistive damping.

    ↳ astro-ph.HEhep-phJCAP(2016)·82 citations
28. 28*

    Time evolution of the anisotropies of the hydrodynamically expanding sQGP

    Attila Bagoly🇭🇺 · Mate Csanad🇭🇺

    In high energy heavy ion collisions of RHIC and LHC, a strongly interacting quark gluon plasma (sQGP) is created. This medium undergoes a hydrodynamic evolution, before it freezes out to form a hadronic matter. The initial state of the sQGP is determined by the initial distribution of the participating nucleons and their interactions. Due to the finite number of nucleons, the initial distribution fluctuates on an event-by-event basis. The transverse plane anisotropy of the initial state can be translated into a series of anisotropy coefficients or eccentricities: second, third, fourth-order anisotropy etc. These anisotropies then evolve in time, and result in measurable momentum-space anisotropies, to be measured with respect to their respective symmetry planes. In this paper we investigate the time evolution of the anisotropies. With a numerical hydrodynamic code, we analyze how the speed of sound and viscosity influence this evolution.

    ↳ nucl-thhep-phInt.J.Mod.Phys.A(2016)·2 citations
29. 29*

    First- and second-order error estimates in Monte Carlo integration

    R. Bakx🇳🇱 · R.H.P. Kleiss🇳🇱 · F. Versteegen🇳🇱

    In Monte Carlo integration an accurate and reliable determination of the numerical intregration error is essential. We point out the need for an independent estimate of the error on this error, for which we present an unbiased estimator. In contrast to the usual (first-order) error estimator, this second-order estimator can be shown to be not necessarily positive in an actual Monte Carlo computation. We propose an alternative and indicate how this can be computed in linear time without risk of large rounding errors. In addition, we comment on the relatively very slow convergence of the second-order error estimate.

    ↳ math.NAcs.NAhep-phComput.Phys.Commun.(2016)·0 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.