Tue·Feb 7, 2017Tuesday·February 7, 2017

1. 01*

   Cosmological Implications of Dark Matter Bound States

   Andrea Mitridate🇮🇹 · Michele Redi🇮🇹 · Juri Smirnov🇮🇹 · Alessandro Strumia🇨🇭

   We present generic formulae for computing how Sommerfeld corrections together with bound-state formation affects the thermal abundance of Dark Matter with non-abelian gauge interactions. We consider DM as a fermion 3plet (wino) or 5plet under SU(2)${}_L$. In the latter case bound states raise to 14 TeV the DM mass required to reproduce the cosmological DM abundance and give indirect detection signals such as (for this mass) a dominant $\gamma$-line around 85 GeV. Furthermore, we consider DM co-annihilating with a colored particle, such as a squark or a gluino, finding that bound state effects are especially relevant in the latter case.

   hep-phJCAP(2017)·176 citations
2. 02*

   Review of experimental and theoretical status of the proton radius puzzle

   Richard J. Hill🇺🇸

   The discrepancy between the measured Lamb shift in muonic hydrogen and expectations from electron-proton scattering and regular hydrogen spectroscopy has become known as the proton radius puzzle, whose most "mundane" resolution requires a $>5\sigma$ shift in the value of the fundamental Rydberg constant. I briefly review the status of spectroscopic and scattering measurements, recent theoretical developments, and implications for fundamental physics.

   hep-phnucl-thphysics.atom-phEPJ Web Conf.(2017)·43 citations
3. 03*

   World-line construction of a covariant chiral kinetic theory

   Niklas Mueller🇩🇪 · Raju Venugopalan🇺🇸

   We discuss a novel world-line framework for computations of the Chiral Magnetic Effect (CME) in ultrarelativistic heavy-ion collisions. Starting from the fermion determinant in the QCD effective action, we show explicitly how its real part can be expressed as a supersymmetric world-line action of spinning, colored, Grassmanian particles in background fields. Restricting ourselves for simplicity to spinning particles, we demonstrate how their constrained Hamiltonian dynamics arises for both massless and massive particles. In a semi-classical limit, this gives rise to the covariant generalization of the Bargmann-Michel-Telegdi equation; the derivation of the corresponding Wong equations for colored particles is straightforward. In a previous letter we outlined how Berry's phase arises in a non-relativistic adiabatic limit for massive particles. We extend the discussion here to systems with a finite chemical potential. We discuss a path integral formulation of the relative phase in the fermion determinant that places it on the same footing as the real part. We construct the corresponding anomalous world-line axial vector current and show in detail how the chiral anomaly appears. Our work provides a systematic framework for a relativistic kinetic theory of chiral fermions in the fluctuating topological backgrounds that generate the CME in a deconfined quark-gluon plasma. We outline some further applications of this framework in many-body systems.

   hep-phhep-thnucl-thPRD(2017)·89 citations
4. 04*

   Charged Higgs bosons from the 3-3-1 models and the $\mathcal{R}(D^{(\ast )})$ anomalies

   Ma Wei🇨🇳 · Yue Chong-Xing🇨🇳

   Several anomalies in the semileptonic B-meson decays such as $\mathcal{R}(D^{(\ast )})$ have been reported by $BABAR$, Belle, and LHCb collaborations recently. In this paper, we investigate the contributions of the charged Higgs bosons from the 3-3-1 models to the $\mathcal{R}(D^{(\ast )})$ anomalies. We find that, in a wide range of parameter space, the 3-3-1 models might give reasonable explanations to the $\mathcal{R}(D^{(\ast )})$ anomalies and other analogous anomalies of the B meson's semileptonic decays.

   hep-phPRD(2017)·35 citations
5. 05*

   Azimuthal correlations of D-mesons in $p$+$p$ and $p$+Pb collisions at LHC energies

   M.Younus🇮🇳 · S.K.Tripathy🇮🇳 · P.K.Sahu🇮🇳 · Z. Naik🇮🇳

   We study the correlations of D mesons produced in $p$+$p$ and $p$+Pb collisions. These are found to be sensitive to the effects of the cold nuclear medium and the transverse momentum ($p_T$) regions we are looking into. In order to put this on a quantitative footing, as a first step we analyse the azimuthal correlations of D meson-charged hadron(Dh), and then predict the same for D meson -anti D meson ($D\overline{D}$) pairs in $p$+$p$ and $p$+Pb collisions with strong coupling at leading order $\mathcal{O}$(${\alpha }_s^2$) and next to leading order $\mathcal{O}$(${\alpha }_s^3$) which includes space-time evolution (in both systems), as well cold nuclear matter effects (in $p$+Pb). This also sets the stage and baseline for the identification and study of medium modification of azimuthal correlations in relativistic collision of heavy nuclei at the Large Hadron Collider.

   hep-phEPJA(2017)·3 citations
6. 06*

   Inhomogeneous chiral condensate in the quark-meson model

   Prabal Adhikari🇺🇸 · Jens O. Andersen🇳🇴 · Patrick Kneschke🇳🇴

   The two-flavor quark-meson model is used as a low-energy effective model for QCD to study inhomogeneous chiral condensates at finite %temperature $T$ baryon chemical potential ${\mu }_B$. The parameters of the model are determined by matching the meson and quark masses, and the pion decay constant to their physical values using the on-shell and modified minimal subtraction schemes. Using a chiral-density wave ansatz for the inhomogeneity, we calculate the effective potential in the mean-field approximation and the result is completely analytic. The size of the inhomogeneous phase depends sensitively on the pion mass and whether one includes the vacuum fluctuations or not. Finally, we briefly discuss the mean-field phase diagram.

   hep-phPRD(2017)·37 citations
7. 07*

   Parton Radiation and Fragmentation from LHC to FCC-ee

   David d'Enterria · Peter Z. Skands · D. Anderle🇬🇧 · F. Anulli🇮🇹 · J. Aparisi🇪🇸 · G. Bell🇩🇪 · V. Bertone🇳🇱 · C. Bierlich🇸🇪 · S. Carrazza🇨🇭 · G. Corcella🇮🇹 · D. d'Enterria · M. Dasgupta🇬🇧 and 44 other authors

   This document collects the proceedings of the "Parton Radiation and Fragmentation from LHC to FCC-ee" workshop (http://indico.cern.ch/e/ee\_jets16) held at CERN in Nov. 2016. The writeup reviews the latest theoretical and experimental developments on parton radiation and parton-hadron fragmentation studies --including analyses of LEP, B-factories, and LHC data-- with a focus on the future perspectives reacheable in $e^{+}{e}^{-}$ measurements at the Future Circular Collider (FCC-ee), with multi-ab${}^{-1}$ integrated luminosities yielding 10${}^{12}$ and 10${}^8$ jets from Z and W bosons decays as well as 10${}^5$ gluon jets from Higgs boson decays. The main topics discussed are: (i) parton radiation and parton-to-hadron fragmentation functions (splitting functions at NNLO, small-$z$ NNLL resummations, global FF fits including Monte Carlo (MC) and neural-network analyses of the latest Belle/BaBar high-precision data, parton shower MC generators), (ii) jet properties (quark-gluon discrimination, $e^{+}{e}^{-}$ event shapes and multi-jet rates at NNLO+N${}^n$LL, jet broadening and angularities, jet substructure at small-radius, jet charge determination, $e^{+}{e}^{-}$ jet reconstruction algorithms), (iii) heavy-quark jets (dead cone effect, charm-bottom separation, gluon-to-$b\bar{b}$ splitting), and (iv) non-perturbative QCD phenomena (colour reconnection, baryon and strangeness production, Bose-Einstein and Fermi-Dirac final-state correlations, colour string dynamics: spin effects, helix hadronization).

   hep-phhep-ex30 citations
8. 08*

   Nested soft-collinear subtractions in NNLO QCD computations

   Fabrizio Caola🇨🇭 · Kirill Melnikov🇩🇪 · Raoul Röntsch🇩🇪

   We discuss a modification of the next-to-next-to-leading order (NNLO) subtraction scheme based on the residue-improved sector decomposition that reduces the number of double-real emission sectors from five to four. In particular, a sector where energies and angles of unresolved particles vanish in a correlated fashion is redundant and can be discarded. This simple observation allows us to formulate a transparent iterative subtraction procedure for double-real emission contributions, to demonstrate the cancellation of soft and collinear singularities in an explicit and (almost) process-independent way and to write the result of a NNLO calculation in terms of quantities that can be computed in four space-time dimensions. We illustrate this procedure explicitly in the simple case of $O({\alpha }_s^2)$ gluonic corrections to the Drell-Yan process of $q\bar{q}$ annihilation into a lepton pair. We show that this framework leads to fast and numerically stable computation of QCD corrections.

   hep-phEPJC(2017)·219 citations
9. 09*

   Estimating the branching fraction for $B^0\to \psi (2S){\pi }^0$ decay

   Behnam Mohammadi🇮🇷

   I present estimates of the branching fractions in the non-leptonic charmonium two-body decay rates for $B^0\to \psi (2S){\pi }^0$ decay and the same decays of $B^{+}\to \psi (2S){\pi }^{+}$, $B^0\to \psi (2S)K^0$ and $B^{+}\to \psi (2S)K^{+}$. These estimates are based on a generalized factorization approach making use of leading order (LO) and next-to-leading order (NLO) contributions. I find that when the large enhancements from the known NLO contributions by using the QCD factorization approach are taken into account, the branching ratios are the following: $Br(B^0\to \psi (2S){\pi }^0)=(1.067\pm 0.059)\times 10^{-5}$, $Br(B^{+}\to \psi (2S){\pi }^{+})=(2.134\pm \mathrm{0.0.118})\times 10^{-5}$, $Br(B^0\to \psi (2S)K^0)=(6.344\pm 0.376)\times 10^{-4}$ and $Br(B^{+}\to \psi (2S)K^{+})=(6.344\pm 0.376)\times 10^{-4}$, while the experimental results are $(1.17\pm 0.17)\times 10^{-5}$, $(2.44\pm 0.30)\times 10^{-5}$, $(6.20\pm 0.50)\times 10^{-4}$ and $(6.39\pm 0.33)\times 10^{-4}$ respectively. All estimates are in good agreement with the experimental results.

   hep-phAIP Conf.Proc.(2017)·2 citations
10. 10*

    Temperature Effect on Shear and Bulk Viscosities of QCD Matter

    Fei Gao🇨🇳 · Yu-xin Liu🇨🇳

    We investigate the temperature dependence of the shear and bulk viscosities and their ratios to the entropy density via a continuum QCD approach. We calculate the pion mass and decay constant in the framework of Dyson-Schwinger equations of QCD and the pion thermal width by combining with Roy equations. We obtain then the variation behaviors of the viscosities, especially a novel feature of the bulk viscosity, with respect to temperature.

    hep-phPRD(2018)·19 citations
11. 11*

    Five-loop fermion anomalous dimension for a general gauge group from four-loop massless propagators

    P. A. Baikov🇷🇺 · K. G. Chetyrkin🇩🇪 · J. H. Kühn🇩🇪

    We extend the $\mathcal{O}({\alpha }_s^5)$ result of the analytic calculation of the quark mass anomalous dimension in pQCD [1] to the case of a generic gauge group. We present explicit formulas which express the relevant renormalization constants in terms of four-loop massless propagators. We also use our result to shed new light on the old puzzle of the absence of even zetas in results of perturbative calculations for a class of physical observables.

    hep-phhep-thJHEP(2017)·97 citations
12. 12*

    Detecting axions via induced electron spin precession

    Stephon Alexander🇺🇸 · Robert Sims🇺🇸

    We propose a new window to detect axion-like particle (ALP) dark matter from electrically charged fermions, such as electrons and quarks. We specifically consider a direct interaction between the axion and the electron and find that the non-relativistic quantum dynamics induces a spin precession due to the axion and is enhanced by the application of an external electric field. This precession gives a change in magnetic flux which under certain circumstances can yield a detectable signal for SQUID magnetometers.

    hep-phastro-ph.HEhep-thPRD(2018)·20 citations
13. 13*

    Dark Matter scenarios at IceCube

    Marco Chianese🇮🇹

    The recent study on the the 6-year up-going muon neutrinos by the IceCube Collaboration and the multi-messenger analyses support the hypothesis of a two-component scenario explaining the diffuse TeV-PeV neutrino flux. Depending on the steepness of the astrophysical power-law, an excess in the IceCube data is shown in the energy range 10-100 TeV (low-energy excess) or at PeV (high-energy excess). In both cases, we characterize a two-component neutrino flux where decaying Dark Matter particles provide a contribution to the IceCube observations.

    hep-phastro-ph.HEPoS(2017)·1 citation
14. 14*

    Detecting the $L_{\mu }-L_{\tau }$ gauge boson at Belle II

    Takeshi Araki🇯🇵 · Shihori Hoshino🇯🇵 · Toshihiko Ota🇯🇵 · Joe Sato🇯🇵 · Takashi Shimomura🇯🇵

    We discuss the feasibility of detecting the gauge boson of the $U(1{)}_{L_{\mu }-L_{\tau }}$ symmetry, which possesses a mass in the range between MeV and GeV, at the Belle-II experiment. The kinetic mixing between the new gauge boson $Z^{\prime }$ and photon is forbidden at the tree level and is radiatively induced. The leptonic force mediated by such a light boson is motivated by the discrepancy in muon anomalous magnetic moment and also the gap in the energy spectrum of cosmic neutrino. Defining the process $e^{+}{e}^{-}\to \gamma Z^{\prime }\to \gamma \nu \bar{\nu }(missingenergy)$ to be the signal, we estimate the numbers of the signal and the background events and show the parameter region to which the Belle-II experiment will be sensitive. The signal process in the $L_{\mu }-L_{\tau }$ model is enhanced with a light $Z^{\prime }$, which is a characteristic feature differing from the dark photon models with a constant kinetic mixing. We find that the Belle-II experiment with the design luminosity will be sensitive to the $Z^{\prime }$ with the mass $M_{Z^{\prime }}\lesssim 1$ GeV and the new gauge coupling $g_{Z^{\prime }}\gtrsim 8\cdot 10^{-4}$, which covers a half of the unconstrained parameter region that explains the discrepancy in muon anomalous magnetic moment. The possibilities to improve the significance of the detection are also discussed.

    hep-phhep-exPRD(2017)·108 citations
15. 15*

    Chiral pair fluctuations for the inhomogeneous chiral transition

    Ryo Yoshiike🇯🇵 · Tong-Gyu Lee🇯🇵 · Toshitaka Tatsumi🇯🇵

    The effects of fluctuations are discussed around the phase boundary of the inhomogeneous chiral transition between the inhomogeneous chiral phase and the chiral-restored phase. The particular roles of thermal and quantum fluctuations are elucidated and a continuity of their effects across the phase boundary is suggested. In addition, it is argued that anomalies in the thermodynamic quantities should have phenomenological implications for the inhomogeneous chiral transition. Some common features for other phase transitions, such as those from the normal to the inhomogeneous Fulde-Ferrell-Larkin-Ovchinnikov state in superconductivity, are also emphasized.

    hep-phPRD(2017)·17 citations
16. 16*

    Constraints of chromoelectric dipole moments to natural SUSY type sfermion spectrum

    Nobuhiro Maekawa🇯🇵 · Yu Muramatsu🇨🇳 · Yoshihiro Shigekami🇯🇵

    We investigate the lower bounds of sfermion masses from the constraints of chromoelectric dipole moments (CEDMs) in the natural SUSY-type sfermion mass spectrum, in which stop mass $m_{\tilde{t}}$ is much smaller than the other sfermion masses $m_0$. The natural SUSY-type sfermion mass spectrum has been studied since the supersymmetric (SUSY) flavor-changing neutral currents (FCNC) are suppressed because of large sfermion masses of the first two generations, and the weak scale is stabilized because of the light stop. However, this type of sfermion mass spectrum is severely constrained by CEDM, because the light stop contributions to the up quark CEDM are not decoupled in the limit $m_0\to \infty$, while the down quark CEDM is decoupled in the limit. It is important that the constraints are severe even if SUSY-breaking parameters (and Higgsino mass) are taken to be real because complex diagonalizing matrices of Yukawa matrices, which are from complex Yukawa couplings, generate nonvanishing CP phases in off-diagonal elements of sfermion mass matrices. We calculate the CEDM of up and down quarks numerically in the minimal SUSY standard model, and give the lower bounds for stop mass and the other sfermion masses. We show that the lower bound of stop mass becomes 7 TeV to satisfy the CEDM constraints from Hg EDM. The result is not acceptable if the weak scale stability is considered seriously. We show that if the up-type Yukawa couplings are taken to be real at the grand unification scale, the CEDM constraints are satisfied even if $m_{\tilde{t}}\sim 1$ TeV.

    hep-phPRD(2017)·5 citations
17. 17*

    Axion Inflation and Affleck-Dine Baryogenesis

    Kensuke Akita🇯🇵 · Tatsuo Kobayashi🇯🇵 · Hajime Otsuka🇯🇵

    String theory generically predicts the coupling between the Affleck-Dine field and axion field through higher-dimensional operators. We thus explore the Affleck-Dine baryogenesis on an axion background. It turns out that the axion oscillation produces an enough amount of baryon asymmetry of the Universe just after the inflation, even without a soft supersymmetry-breaking $A$-term. This baryogenesis scenario is applicable to the string axion inflation.

    hep-phastro-ph.COhep-thJCAP(2017)·22 citations
18. 18*

    Optimal choice of factorization scales for the description of jet production at the LHC

    A.D. Martin🇬🇧 · M.G. Ryskin🇬🇧

    To obtain more precise parton distribution functions (PDFs) it is important to include data on inclusive high transverse energy jet production in the global parton analyses. These data have high statistics and the NNLO terms in the perturbative QCD (pQCD) description are now available. Our aim is to reduce the uncertainty in the comparison of the jet data with pQCD. To ensure the best convergence of the pQCD series it is important to choose the appropriate factorization scales, ${\mu }_F$. We show that it is possible to absorb and resum in the incoming PDFs and fragmentation function ($D$) an essential part of the higher ${\alpha }_s$ order corrections by determining the `optimal' values of ${\mu }_F$. We emphasize that it is necessary to optimize different factorization scales for the various factors in the cross section: indeed, both of the PDFs, and also the fragmentation function, have their own optimal scale. We show how the values of these scales can be calculated for the LO (NLO) part of the pQCD prediction of the cross section based on the theoretically known NLO (NNLO) corrections. After these scales are fixed at their optimal values, the residual factorization scale dependence is much reduced.

    hep-phEPJC(2017)·2 citations
19. 19*

    Evaluation of CKM matrix elements from exclusive $P_{\ell 4}$ decays

    C. S. Kim🇰🇷 · G. López Castro🇲🇽 · S. L. Tostado🇲🇽

    We consider the exclusive $P_{\ell 4}$ decays, $P\to (P_1{P}_2{)}_V\ell {\nu }_{\ell }$, where the subindex $V$ means that the invariant mass of the pseudoscalar pair is taken within a small window around the mass of the vector meson $V$. Pole contributions beyond the dominant $P\to V(\to P_1{P}_2)\ell {\nu }_{\ell }$ amplitude of $P_{\ell 4}$ decays are identified, which, in turn, affects the determination of the CKM matrix elements $|V_{q{q}^{\prime }}|$. We evaluate the effects of those contributions in the extraction of bottom and charm quark mixings. An application to $B\to (\pi \pi {)}_{\rho }\ell {\nu }_{\ell }$ data from Belle collaboration, shows an increase in the extracted value of $|V_{ub}|$ in better agreement with determinations based on $B\to \pi \ell {\nu }_{\ell }$ decays. The effect of the $\rho$ and $D^{\ast }$ pole contributions in the determination of $|V_{cd}|$ from the decay $D\to \pi \pi {\ell }^{-}{\bar{\nu }}_{\ell }$, has been also investigated.

    hep-phPRD(2017)·9 citations
20. 20*

    Target Mass Effects in Parton Quasi-Distributions

    Anatoly Radyushkin🇺🇸

    We study the impact of non-zero (and apparently large) value of the nucleon mass $M$ on the shape of parton quasi-distributions $Q(y,p_3)$, in particular on its change with the change of the nucleon momentum $p_3$. We observe that the usual target-mass corrections induced by the $M$-dependence of the twist-2 operators are rather small. Moreover, we show that within the framework based on parametrizations by transverse momentum dependent distribution functions (TMDs) these corrections are canceled by higher-twist contributions. We identify a novel source of kinematic target-mass dependence of TMDs and build models corrected for such dependence. We find that resulting changes may be safely neglected for $p_3\gtrsim 2M$.

    hep-phhep-latPLB(2017)·38 citations
21. 21*

    Directions for model building from asymptotic safety

    Andrew D. Bond🇬🇧 · Gudrun Hiller🇩🇪 · Kamila Kowalska🇩🇪 · Daniel F. Litim🇬🇧

    Building on recent advances in the understanding of gauge-Yukawa theories we explore possibilities to UV-complete the Standard Model in an asymptotically safe manner. Minimal extensions are based on a large flavor sector of additional fermions coupled to a scalar singlet matrix field. We find that asymptotic safety requires fermions in higher representations of $SU(3{)}_C\times SU(2{)}_L$. Possible signatures at colliders are worked out and include $R$-hadron searches, diboson signatures and the evolution of the strong and weak coupling constants.

    hep-phhep-exhep-thJHEP(2017)·95 citations
22. 22*

    Constraints on the trilinear Higgs self coupling from precision observables

    Giuseppe Degrassi🇮🇹 · Marco Fedele🇮🇹 · Pier Paolo Giardino🇺🇸

    We present the constraints on the trilinear Higgs self coupling that arise from loop effects in the $W$ boson mass and the effective sine predictions. We compute the contributions to these precision observables of two-loop diagrams featuring an anomalous trilinear Higgs self coupling. We explicitly show that the same anomalous contributions are found if the analysis of $m_W$ and \mbox{\sin^2 \theta^{{\rm lep}}_{{\rm eff}}} is performed in a theory in which the scalar potential in the Standard Model Lagrangian is modified by an (in)finite tower of $({\Phi }^{†}\Phi {)}^n$ terms with $\Phi$ the Higgs doublet. We find that the bounds on the trilinear Higgs self coupling from precision observables are competitive with those coming from Higgs pair production.

    hep-phJHEP(2017)·79 citations
23. 23*

    Prospects of Light Sterile Neutrino Oscillation and CP Violation Searches at the Fermilab Short Baseline Neutrino Facility

    Davio Cianci🇺🇸 · Andy Furmanski🇬🇧 · Georgia Karagiorgi🇺🇸 · Mark Ross-Lonergan🇬🇧

    We investigate the ability of the Short Baseline Neutrino (SBN) experimental program at Fermilab to test the globally-allowed (3+$N$) sterile neutrino oscillation parameter space. We explicitly consider the globally-allowed parameter space for the (3+1), (3+2), and (3+3) sterile neutrino oscillation scenarios. We find that SBN can probe with $5\sigma$ sensitivity more than 85\%, 95\% and 55\% of the parameter space currently allowed at 99\% confidence level for the (3+1), (3+2) and (3+3) scenarios, respectively. In the case of the (3+2) and (3+3) scenarios, CP-violating phases appear in the oscillation probability terms, leading to observable differences in the appearance probabilities of neutrinos and antineutrinos. We explore SBN's sensitivity to those phases for the (3+2) scenario through the currently planned neutrino beam running, and investigate potential improvements through additional antineutrino beam running. We show that, if antineutrino exposure is considered, for maximal values of the (3+2) CP-violating phase ${\varphi }_{54}$, SBN could be the first experiment to directly observe $\sim 2\sigma$ hints of CP violation associated with an extended lepton sector.

    hep-phPRD(2017)·39 citations
24. 24*

    Diffuse cosmic rays shining in the Galactic center: A novel interpretation of H.E.S.S. and Fermi-LAT gamma-ray data

    D. Gaggero🇳🇱 · D. Grasso🇮🇹 · A. Marinelli🇮🇹 · M. Taoso🇪🇸 · A. Urbano🇨🇭

    We present a novel interpretation of the $\gamma$-ray diffuse emission measured by Fermi-LAT and H.E.S.S. in the Galactic center (GC) region and the Galactic ridge (GR). In the first part we perform a data-driven analysis based on PASS8 Fermi-LAT data: we extend down to few GeV the spectra measured by H.E.S.S. and infer the primary cosmic-ray (CR) radial distribution between 0.1 and 3 TeV. In the second part we adopt a CR transport model based on a position-dependent diffusion coefficient. Such behavior reproduces the radial dependence of the CR spectral index recently inferred from the Fermi-LAT observations. We find that the bulk of the GR emission can be naturally explained by the interaction of the diffuse steady-state Galactic CR sea with the gas present in the Central Molecular Zone. Although our results leave room for a residual radial-dependent emission associated with a central source, the relevance of the large-scale background prevents from a solid evidence of a GC Pevatron.

    ↳ astro-ph.HEhep-phPRL(2017)·105 citations
25. 25*

    Fluctuations in ultra-relativistic heavy ion collisions

    Aleksas Mazeliauskas🇺🇸

    Fluctuations are one of the main probes of the physics of the new state of hot and dense nuclear matter called the Quark Gluon Plasma (QGP) which is created in the ultra-relativistic heavy ion collisions. In this dissertation we extend and improve upon the existing descriptions of heavy ion collisions in three different directions: we study the new signatures of initial state fluctuations, the propagation of perturbations in the early stages of the collision, and the effect of thermal fluctuations on the hydrodynamic expansion of the QGP. First, we use Principal Component Analysis (PCA) to study event-by-event fluctuations in the spectrum of harmonic flow, $v_n(p_T)$ for $n=0\text{–}5$, in hydrodynamic simulations of Pb+Pb collisions at the CERN Large Hadron Collider ($\sqrt{s_{NN}}=2.76\mathrm{TeV}$). The PCA procedure finds two dominant contributions to the two-particle correlation function: the leading component is identified with the standard event plane $v_n(p_T)$ and the subleading component is responsible for factorization breaking and reflects the radial excitation in the initial state. Second, we use leading order effective kinetic theory (accurate at weak coupling) to simulate the pre-equilibrium evolution of transverse energy and flow perturbations. We construct the linear response Green functions, which map initial perturbations to the energy momentum tensor at a time when hydrodynamics becomes applicable. Finally, we develop a set of kinetic equations for thermal noise correlators which are equivalent to nonlinear hydrodynamics with noise. We use the hydro-kinetic equations to analyze thermal fluctuations for a Bjorken expansion and determine the coefficient of the first fractional power ($\propto 1/(\tau T{)}^{3/2}$) of the nonlinear noise corrections to energy momentum tensor.

    ↳ nucl-thhep-ph2 citations
26. 26*

    Spin asymmetry for proton-deuteron Drell-Yan process with tensor-polarized deuteron

    S. Kumano🇯🇵 · Qin-Tao Song🇯🇵

    Tensor structure of the deuteron can be studied by deep inelastic scattering and Drell-Yan process to understand it in terms of quark and gluon degrees of freedom. It probes interesting features in the deuteron including a D-wave contribution. In the charged-lepton DIS, twist-two structure functions $b_1$ and $b_2$ are expressed by tensor-polarized parton distribution functions (PDFs). We note that the HERMES experimental measurement of $b_1$ seems to be much different from a conventional theoretical prediction. This puzzling situation should be significantly improved in the near future by an approved experiment to measure $b_1$ at JLab. On the other hand, the tensor-polarized PDFs, especially antiquark distributions, could be measured by spin asymmetries in the Drell-Yan process with a tensor-polarized deuteron at Fermilab. In this work, we estimate tensor-polarization asymmetries for the Fermilab Drell-Yan experiment by using a parametrization for the tensor-polarized PDFs to explain the HERMES $b_1$ data. Obtained spin asymmetries are typically a few percent order and they could be measured by the Fermilab-E1039 experiment. Since the tensor-polarized antiquark distributions will play an important role to solve the puzzle, further theoretical and experimental efforts are needed toward the Drell-Yan experiment at Fermilab and other hadron facilities.

    ↳ nucl-thhep-lathep-phnucl-ex7 citations
27. 27*

    Feasibility Studies for Single Transverse-Spin Asymmetry Measurements at a Fixed-Target Experiment Using the LHC Proton and Lead Beams (AFTER@LHC)

    Daniel Kikoła🇵🇱 · Miguel García Echevarria🇪🇸 · Cynthia Hadjidakis🇫🇷 · Jean-Philippe Lansberg🇫🇷 · Cedric Lorcé🇫🇷 · Laure Massacrier🇫🇷 · Catarina Marques Quintans🇵🇹 · Andrea Signori🇺🇸 · Barbara Trzeciak🇳🇱

    The measurement of Single Transverse-Spin Asymmetries, $A_N$, for various quarkonium states and Drell-Yan lepton pairs can shed light on the orbital angular momentum of quarks and gluons, a fundamental ingredient of the proton-spin puzzle. The AFTER@LHC proposal combines a unique kinematic coverage and large luminosities thanks to the Large Hadron Collider beams to deliver precise measurements, complementary to the knowledge provided by collider experiments such as at RHIC. In this paper, we report on sensitivity studies for $J/\psi$, ${\rm Y}$ and Drell-Yan $A_N$ done using the performance of LHCb-like or ALICE-like detectors, combined with polarised gaseous hydrogen and helium-3 targets. In particular, such analyses will provide us with new insights and knowledge about transverse-momentum-dependent parton distribution functions for quarks and gluons and on twist-3 collinear matrix elements in the proton and the neutron.

    ↳ hep-exhep-phnucl-exnucl-thFew Body Syst.(2017)·44 citations
28. 28*

    Baryon interactions from lattice QCD with physical masses -- Overview and $S=0,-4$ sectors --

    Takumi Doi🇯🇵 · Sinya Aoki🇯🇵 · Shinya Gongyo🇯🇵 · Tetsuo Hatsuda🇯🇵 · Yoichi Ikeda🇯🇵 · Takashi Inoue🇯🇵 · Takumi Iritani🇯🇵 · Noriyoshi Ishii🇯🇵 · Takaya Miyamoto🇯🇵 · Keiko Murano🇯🇵 · Hidekatsu Nemura🇯🇵 · Kenji Sasaki🇯🇵

    Nuclear forces and hyperon forces are studied by lattice QCD. Simulations are performed with (almost) physical quark masses, $m_{\pi }\simeq 146$ MeV and $m_K\simeq 525$ MeV, where $N_f=2+1$ nonperturbatively $\mathcal{O}(a)$-improved Wilson quark action with stout smearing and Iwasaki gauge action are employed on the lattice of $(96a{)}^4\simeq (8.1\text{mbox}fm{)}^4$ with $a^{-1}\simeq 2.3$ GeV. In this report, we give the overview of the theoretical framework and present the numerical results for two-nucleon forces ($S=0$) and two-$\Xi$ forces ($S=-4$). Central forces are studied in ${}^1{S}_0$ channel, and central and tensor forces are obtained in ${}^3{S}_1$-${}^3{D}_1$ coupled channel analysis.

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

    Relative flow fluctuations as a probe of initial state fluctuations

    Giuliano Giacalone🇫🇷 · Jacquelyn Noronha-Hostler🇺🇸 · Jean-Yves Ollitrault🇫🇷

    Elliptic flow, $v_2$, and triangular flow, $v_3$, are to a good approximation linearly proportional to the corresponding spatial anisotropies of the initial density profile, ${\epsilon }_2$ and ${\epsilon }_3$. Using event-by-event hydrodynamic simulations, we point out when deviations from this linear scaling are to be expected. When these deviations are negligible, relative $v_n$ fluctuations are equal to relative ${\epsilon }_n$ fluctuations, and one can directly probe models of initial conditions using ratios of cumulants, for instance $v_n\{4\}/v_n\{2\}$. We argue that existing models of initial conditions tend to overestimate flow fluctuations in central Pb+Pb collisions, and to underestimate them in peripheral collisions. We make predictions for $v_3\{6\}$ in noncentral Pb+Pb collisions, and for $v_3\{4\}$ and $v_3\{6\}$ in high-multiplicity p+Pb collisions.

    ↳ nucl-thhep-phnucl-exPRC(2017)·101 citations
30. 30*

    Higher-order anisotropies in the Blast-Wave Model - disentangling flow and density field anisotropies

    Jakub Cimerman🇨🇿 · Boris Tomasik🇸🇰 · Mate Csanad🇭🇺 · Sandor Lokos🇭🇺

    We formulate a generalisation of the blast-wave model which is suitable for the description of higher order azimuthal anisotropies of the hadron production. The model includes anisotropy in the density profile as well as an anisotropy in the transverse expansion velocity field. We then study how these two kinds of anisotropies influence the single-particle distributions and the correlation radii of two-particle correlation functions. Particularly we focus on the third-order anisotropy and consideration is given to the averaging over different orientation of the event plane.

    ↳ nucl-thhep-exhep-phEPJA(2017)·23 citations
31. 31*

    Probing the Gravitational Dependence of the Fine-Structure Constant from Observations of White Dwarf Stars

    Matthew B. Bainbridge🇬🇧 · Martin A. Barstow🇬🇧 · Nicole Reindl🇬🇧 · W.-Ü Lydia Tchang-Brillet🇫🇷 · Thomas R. Ayres🇺🇸 · John K. Webb🇦🇺 · John D. Barrow🇬🇧 · Jiting Hu🇦🇺 · Jay B. Holberg🇺🇸 · Simon P. Preval🇬🇧 · Wim Ubachs🇳🇱 · Vladimir A. Dzuba🇦🇺 and 3 other authors

    Hot white dwarf stars are the ideal probe for a relationship between the fine-structure constant and strong gravitational fields, providing us with an opportunity for a direct observational test. We study a sample of hot white dwarf stars, combining far-UV spectroscopic observations, atomic physics, atmospheric modelling and fundamental physics, in the search for variation in the fine structure constant. This variation manifests as shifts in the observed wavelengths of absorption lines, such as quadruply ionized iron (FeV) and quadruply ionized nickel (NiV), when compared to laboratory wavelengths. Berengut et al. (Phys. Rev. Lett. 2013, 111, 010801) demonstrated the validity of such an analysis using high-resolution Hubble Space Telescope (HST)/Space Telescope Imaging Spectrograph (STIS) spectra of G191-B2B. We have made three important improvements by: (a) using three new independent sets of laboratory wavelengths, (b) analysing a sample of objects, and (c) improving the methodology by incorporating robust techniques from previous studies towards quasars (the Many Multiplet method). A successful detection would be the first direct measurement of a gravitational field effect on a bare constant of nature. Here we describe our approach and present preliminary results from nine objects using both FeV and NiV.

    ↳ astro-ph.COgr-qchep-phhep-thUniverse(2017)·30 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.