Wed·May 25, 2016Wednesday·May 25, 2016

1. 01*

   3-D Glasma initial state for relativistic heavy ion collisions

   Bjoern Schenke🇺🇸 · Soeren Schlichting🇺🇸

   We extend the impact parameter dependent Glasma model (IP-Glasma) to three dimensions using explicit small x evolution of the two incoming nuclear gluon distributions. We compute rapidity distributions of produced gluons and the early time energy momentum tensor as a function of space-time rapidity and transverse coordinates. We study rapidity correlations and fluctuations of the initial geometry and multiplicity distributions and compare to existing models for the three dimensional initial state.

   hep-phnucl-thPRC(2016)·110 citations
2. 02*

   Photoproduction of leptophobic bosons

   Cristiano Fanelli🇺🇸 · Mike Williams🇺🇸

   We propose a search for photoproduction of leptophobic bosons that couple to quarks at the GlueX experiment at Jefferson Lab. We study in detail a new gauge boson that couples to baryon number $B$, and estimate that $\gamma p\to pB$ will provide the best sensitivity for $B$ masses above 0.5 GeV. This search will also provide sensitivity to other proposed dark-sector states that couple to quarks. Finally, our results motivate a similar search for $B$ boson electroproduction at the CLAS experiment.

   hep-phhep-exnucl-exJ.Phys.G(2017)·19 citations
3. 03*

   One loop contributions to neutral Higgs decay h-->mu tau

   K. H. Phan🇻🇳 · H.T. Hung🇻🇳 · L.T. Hue🇻🇳

   In calculating one-loop contributions to amplitudes of the lepton-flavor violating decays of the neutral Higgses (LFVHD) to different flavor charged leptons, the analytic expressions can be written in term of Passarino-Veltman functions. Then, they can be computed numerically by Looptools [1]. Another approach is using suitable analytic expressions established for just this particular case. We compare numerical results obtained from Looptools and those computed by different expressions that have been applied recently. Then we derive the preferable ones that are applicable for the large ranges of free parameters introduced in the models beyond the Standard Model (SM). For illustration, the LFVHD in a simple model, which has been discussed recently, will be investigated more precisely.

   hep-phPTEP(2016)·18 citations
4. 04*

   Next-to-leading order transverse momentum broadening for Drell-Yan production in p+A collisions

   Zhong-Bo Kang🇺🇸 · Jian-Wei Qiu🇺🇸 · Xin-Nian Wang🇨🇳 · Hongxi Xing🇺🇸

   We present the nuclear transverse momentum broadening for Drell-Yan lepton pair production in p+A collisions at next-to-leading order (NLO) in powers of strong coupling constant ${\alpha }_s$. We verify that the transverse momentum weighted differential cross section in NLO perturbative QCD (pQCD) at twist-4 can be factorized into the convolution of parton distribution function of an active parton in the projectile proton, a twist-4 multiparton correlation function of the target nucleus, and perturbatively calculable hard coefficient function. We identify a QCD evolution equation for such a twist-4 nuclear gluon-quark correlation function, and verify its universality -- its process independence. This finding demonstrates the prediction power of pQCD factorization approach for studying parton multiple scattering in nuclear medium.

   hep-phnucl-thPRD(2016)·20 citations
5. 05*

   Phenomenology of Strongly Coupled Chiral Gauge Theories

   Yang Bai🇺🇸 · Joshua Berger🇺🇸 · James Osborne🇺🇸 · Ben A. Stefanek🇺🇸

   A sector with QCD-like strong dynamics is common in models of non-standard physics. Such a model could be accessible in LHC searches if both confinement and big-quarks charged under the confining group are at the TeV scale. Big-quark masses at this scale can be explained if the new fermions are chiral under a new $U(1{)}^{\prime }$ gauge symmetry such that their bare masses are related to the $U(1{)}^{\prime }$-breaking and new confinement scales. Here we present a study of a minimal GUT-motivated and gauge anomaly-free model with implications for the LHC Run 2 searches. We find that the first signatures of such models could appear as two gauge boson resonances. The chiral nature of the model could be confirmed by observation of a $Z^{\prime }\gamma$ resonance, where the $Z^{\prime }$ naturally has a large leptonic branching ratio because of its kinetic mixing with the hypercharge gauge boson.

   hep-phhep-exJHEP(2016)·13 citations
6. 06*

   Simulating collisions of thick nuclei in the color glass condensate framework

   Daniil Gelfand🇦🇹 · Andreas Ipp🇦🇹 · David Müller🇦🇹

   We present our work on the simulation of the early stages of heavy-ion collisions with finite longitudinal thickness in the laboratory frame in 3+1 dimensions. In particular we study the effects of nuclear thickness on the production of a glasma state in the McLerran-Venugopalan model within the color glass condensate framework. A finite thickness enables us to describe nuclei at lower energies, but forces us to abandon boost-invariance. As a consequence, random classical color sources within the nuclei have to be included in the simulation, which is achieved by using the colored particle-in-cell (CPIC) method. We show that the description in the laboratory frame agrees with boost-invariant approaches as a limiting case. Furthermore we investigate collisions beyond boost-invariance, in particular the pressure anisotropy in the glasma.

   hep-phnucl-thPRD(2016)·41 citations
7. 07*

   Sharing but not Caring: Dark Matter and the Baryon Asymmetry of the Universe

   Nicolás Bernal🇧🇷 · Chee Sheng Fong🇧🇷 · Nayara Fonseca🇧🇷

   We consider scenarios where Dark Matter (DM) particles carry baryon and/or lepton numbers, which can be defined if there exist operators connecting the dark to the visible sector. As a result, the DM fields become intimately linked to the Standard Model (SM) ones and can be maximally asymmetric just like the ordinary matter. In particular, we discuss minimal scenarios where the DM is a complex scalar or a Dirac fermion coupled to operators with nonzero baryon and/or lepton numbers, and that consist of only SM fields. We consider an initial asymmetry stored in either the SM or the DM sector; the main role of these operators is to properly $share$ the asymmetry between the two sectors, in accordance with observations. After the chemical decoupling, the DM and SM sectors do $not$ $care$ about each other as there is only an ineffective communication between them. Once the DM mass is specified, the Wilson coefficients of these operators are fixed by the requirement of the correct transfer of the asymmetry. We study the phenomenology of this framework at colliders, direct detection and indirect detection experiments. In particular, the LHC phenomenology is very rich and can be tested in different channels such as the two same-sign leptons with two jets, monojet and monojet with a monolepton.

   hep-phJCAP(2016)·14 citations
8. 08*

   Correlating new physics signals in $B\to D^{(\ast )}\tau {\nu }_{\tau }$ with $B\to \tau {\nu }_{\tau }$

   Soumitra Nandi🇮🇳 · Sunando K. Patra🇮🇳 · Amarjit Soni🇺🇸

   Semileptonic and purely leptonic decays of B meson to $\tau$, such as $B\to D^{(\ast )}\tau {\nu }_{\tau }$ and $B\to \tau {\nu }_{\tau }$ are studied. Recognizing that there already were some weak hints of possible deviations from the SM in the measurements of $\mathcal{B}(B\to \tau {\nu }_{\tau })$ by \Babar~and Belle and the fact that detection of the $\tau$ also occurs in the measurements of $B\to D^{(\ast )}\tau {\nu }_{\tau }$, we stress the importance of joint studies of these processes, whenever possible. For this purpose, as an illustration, we introduce the observable, $\mathcal{R}(D^{(\ast )})/\mathcal{B}(B\to \tau {\nu }_{\tau })$ where, for one thing, the unknown systematics due to $\tau$ identification are expected to largely cancel. We show that all measurements of this observable are consistent with the existing data, within somewhat largish experimental errors, with the predictions of the SM. We stress that precise experimental measurement and comparison with theory of the branching ratio for $B\to \tau {\nu }_{\tau }$ is extremely important for a reliable search of new physics. Furthermore, in view of the anticipated improved precision in experiments in the next few years, in addition to $\mathcal{R}(D^{(\ast )})$, host of other ratios analogous to $\mathcal{R}(D^{(\ast )})/\mathcal{B}(B\to \tau {\nu }_{\tau })$ in the SM are suggested for lattice calculations as well, so that for more stringent tests of the SM, correlations in lattice calculations can be properly taken into account to enhance precision.

   hep-phhep-exhep-lat31 citations
9. 09*

   Underlying event sensitive observables in Drell-Yan production using GENEVA

   Simone Alioli🇨🇭 · Christian W. Bauer🇺🇸 · Sam Guns🇺🇸 · Frank J. Tackmann🇩🇪

   We present an extension of the GENEVA Monte Carlo framework to include multiple parton interactions (MPI) provided by PYTHIA8. This allows us to obtain predictions for underlying-event sensitive measurements in Drell-Yan production, in conjunction with GENEVA's fully-differential NNLO calculation, NNLL' resummation for the 0-jet resolution variable (beam thrust), and NLL resummation for the 1-jet resolution variable. We describe the interface with the parton shower algorithm and MPI model of PYTHIA8, which preserves both the precision of partonic N-jet cross sections in GENEVA as well as the shower accuracy and good description of soft hadronic physics of PYTHIA8. We present results for several underlying-event sensitive observables and compare to data from ATLAS and CMS as well as to standalone PYTHIA8 predictions. This includes a comparison with the recent ATLAS measurement of the beam thrust spectrum, which provides a potential avenue to fully disentangle the physical effects from the primary hard interaction, primary soft radiation, multiple parton interactions, and nonperturbative hadronization.

   hep-phhep-exEPJC(2016)·27 citations
10. 10*

    Cosmological Constraints on Decoupled Dark Photons and Dark Higgs

    Joshua Berger🇺🇸 · Karsten Jedamzik🇫🇷 · Devin G. E. Walker🇺🇸

    Any neutral boson such as a dark photon or dark Higgs that is part of a non-standard sector of particles can mix with its standard model counterpart. When very weakly mixed with the Standard Model, these particles are produced in the early Universe via the freeze-in mechanism and subsequently decay back to standard model particles. In this work, we place constraints on such mediator decays by considering bounds from Big Bang nucleosynthesis and the cosmic microwave background radiation. We find both nucleosynthesis and CMB can constrain dark photons with a kinetic mixing parameter between log {\epsilon} ~ -10 to -17 for masses between 1 MeV and 100 GeV. Similarly, the dark Higgs mixing angle {\epsilon} with the Standard Model Higgs is constrained between log {\epsilon} ~ -6 to -15. Dramatic improvement on the bounds from CMB spectral distortions can be achieved with proposed experiments such as PIXIE.

    hep-phastro-ph.COJCAP(2016)·95 citations
11. 11*

    Linear $\sigma$ model for the Goldstone Higgs - Experimental tests

    Sara Saa🇪🇸

    In order to explore a possible dynamical nature for the Higgs field (such as its being a pseudo-Goldstone boson) we develop a renormalizable Lagrangian based on the minimal $SO(5)$ linear $\sigma$-model with the symmetry softly broken to $SO(4)$, including gauge bosons and fermions. We then present the phenomenological implications and constraints from precision observables and the impact on present and future LHC data.

    hep-ph0 citations
12. 12*

    LHC signatures of neutral pseudo-Goldstone boson in the E6CHM

    R. Nevzorov🇦🇺 · A. W. Thomas🇦🇺

    The breakdown of the SU(6) global symmetry to its SU(5) subgroup, that contains the standard model (SM) gauge group, in the E6 inspired composite Higgs model (E6CHM) results in a set of pseudo-Nambu-Goldstone bosons (pNGBs). This set, in particular, involves the SM-like Higgs doublet and a SM singlet boson. In the limit when CP is conserved the SM singlet scalar A is a CP-odd state that does not mix with the SM-like Higgs. The interactions of A with exotic matter beyond the SM, which ensures anomaly cancellation and approximate gauge coupling unification, can induce couplings of this pseudoscalar to the SM gauge bosons. We specify the interactions of the SM singlet pNGB state with the exotic vector-like fermions, top quark and SM gauge bosons. Also we explore the dependence of the branching ratios of the pseudoscalar A and its LHC production cross section on the parameters of the E6CHM.

    hep-phhep-exJ.Phys.G(2017)·14 citations
13. 13*

    Electroweak Vacuum Stabilized by Moduli during/after Inflation

    Yohei Ema🇯🇵 · Kyohei Mukaida🇯🇵 · Kazunori Nakayama🇯🇵

    It is known that the present electroweak vacuum is likely to be metastable and it may lead to a serious instability during/after inflation. We propose a simple solution to the problem of vacuum instability during/after inflation. If there is a moduli field which has Planck-suppressed interactions with the standard model fields, the Higgs quartic coupling in the early universe naturally takes a different value from the present one. A slight change of the quartic coupling in the early universe makes the Higgs potential absolutely stable and hence we are free from the vacuum instability during/after inflation.

    hep-phastro-ph.COPLB(2016)·22 citations
14. 14*

    Electroweak-Skyrmion as Topological Dark Matter

    Ryuichiro Kitano🇯🇵 · Masafumi Kurachi🇯🇵

    We show the existence of a nontrivial topological configuration of the Higgs field in the Standard Model with the Skyrme term. It is shown that the current upper bound of the mass of the topological object is about 34 TeV. We discuss the impact of the existence of the topological object on cosmology.

    hep-phJHEP(2016)·14 citations
15. 15*

    Analytic structure of QCD propagators in Minkowski space

    Fabio Siringo🇮🇹

    Analytical functions for the propagators of QCD, including a set of chiral quarks, are derived by a one-loop massive expansion in the Landau gauge, deep in the infrared. By analytic continuation, the spectral functions are studied in Minkowski space, yielding a direct proof of positivity violation and confinement from first principles.The dynamical breaking of chiral symmetry is described on the same footing of gluon mass generation, providing a unified picture. While dealing with the exact Lagrangian, the expansion is based on massive free-particle propagators, is safe in the infrared and is equivalent to the standard perturbation theory in the UV. By dimensional regularization, all diverging mass terms cancel exactly without including mass counterterms that would spoil the gauge and chiral symmetry of the Lagrangian. Universal scaling properties are predicted for the inverse dressing functions and shown to be satisfied by the lattice data. Complex conjugated poles are found for the gluon propagator, in agreement with the i-particle scenario.

    hep-phhep-lathep-thPRD(2016)·73 citations
16. 16*

    The top threshold effect in the $\gamma \gamma$ production at the LHC

    Shashikant R. Dugad🇮🇳 · Pankaj Jain🇮🇳 · Subhadip Mitra🇮🇳 · Prasenjit Sanyal🇮🇳 · Ravindra K. Verma🇮🇳

    We compute the top quark threshold contributions to the $\gamma \gamma$ production at the LHC. They appear when the invariant mass of the photon pair, $M_{\gamma \gamma }$ just exceeds two times the mass of the top quark and induce some feature in the $M_{\gamma \gamma }$ distribution. We determine the magnitude of this threshold effect and characterize this feature with a simple empirical fitting function to show that it is possible to observe this effect at the LHC in future. We also explore some possible improvements that may enhance its significance.

    hep-phEPJC(2018)·12 citations
17. 17*

    Searching for hidden-charm baryonium signals in QCD sum rules

    Hua-Xing Chen🇨🇳 · Dan Zhou🇨🇳 · Wei Chen🇨🇦 · Xiang Liu🇨🇳 · Shi-Lin Zhu🇨🇳

    We give an explicit QCD sum rule investigation to hidden-charm baryonium states with the quark content $u\bar{u}d\bar{d}c\bar{c}$, spin $J=0/1/2/3$, and of both positive and negative parities. We systematically construct the relevant local hidden-charm baryonium interpolating currents, which can actually couple to various structures, including hidden-charm baryonium states, charmonium states plus two pions, and hidden-charm tetraquark states plus one pion, etc. We do not know which structure these currents couple to at the beginning, but after sum rule analyses we can obtain some information. We find some of them can couple to hidden-charm baryonium states, using which we evaluate the masses of the lowest-lying hidden-charm baryonium states with quantum numbers $J^P=2^{-}/3^{-}/0^{+}/1^{+}/2^{+}$ to be around 5.0 GeV. We suggest to search for hidden-charm baryonium states, especially the one of $J=3^{-}$, in the $D$-wave $J/\psi \pi \pi$ and $P$-wave $J/\psi \rho$ and $J/\psi \omega$ channels in this energy region.

    hep-phhep-exhep-latEPJC(2016)·20 citations
18. 18*

    Twisted superspace: Non-renormalization and fermionic symmetries in certain (heterotic string inspired) non-supersymmetric field theories

    Stefan Groot Nibbelink🇩🇪 · Erik Parr🇩🇪

    Inspired by the tachyon-free non-supersymmetric heterotic SO(16)xSO(16) string we consider a special class of non-supersymmetric field theories: Those that can be obtained from supersymmetric field theories by supersymmetry breaking twists. We argue that such theories, like their supersymmetric counter parts, may still possess some fermionic symmetries as left-overs of the super gauge transformations and have special one-loop non-renormalization properties due to holomorphicity. In addition, we extend the supergraph techniques to these theories to calculate some explicit supersymmetry-breaking corrections.

    hep-phhep-thPRD(2016)·21 citations
19. 19*

    Instanton-dyon Ensembles III: Exotic Quark Flavors

    Rasmus Larsen🇺🇸 · Edward Shuryak🇺🇸

    "Exotic quarks" in the title refers to a modification of quark periodicity condition on the thermal circle by introduction of some phases -- known also as "flavor holonomies" -- different quark flavors. These phases provide a valuable tool, to be used for better understanding of deconfinement and chiral restoration phase transitions: by changing them one can dramatically modify both phase transitions. In the language of instanton constituents -- instanton-dyons or monopoles -- it has a very direct explanation: the interplay of flavor and color holonomies can switch topological zero modes between various dyon types. The model we will study in detail, the so called $Z_{N_c}$-symmetric QCD model with equal number of colors and flavors $N_c=N_f=2$ and special arrangement of flavor and color holonomies, ensure "most democratic" setting, in which each quark flavor and each dyon type are in one-to-one correspondence. The usual QCD has the opposite "most exclusive" arrangement: all quarks are antiperiodic and thus all zero modes fall on only one -- twisted or $L$ -- dyon type. As we show by ensemble simulation, deconfinement and chiral restoration phase transitions in these two models are dramatically different. In the usual QCD both are smooth crossovers: but in the case of $Z_2$-symmetric model deconfinement becomes strong first order transition, while chiral symmetry remains broken for all dyon densities studied. These results are in good correspondence with those from recent lattice simulations.

    hep-phPRD(2016)·15 citations
20. 20*

    The Feynman rules for neutrinos and new neutralinos in BLMSSM

    Xing-Xing Dong🇨🇳 · Shu-Min Zhao🇨🇳 · Hai-Bin Zhang🇨🇳 · Fang Wang🇨🇳 · Tai-Fu Feng🇨🇳

    In a supersymmetric extension of the standard model where baryon and lepton numbers are local gauge symmetries(BLMSSM), we deduce the Feynman rules for neutrinos and new neutralinos. We briey introduce the mass matrices for the particles and the related couplings in this work, which are very useful to research the neutrinos and new neutralinos.

    hep-phCPC(2016)·7 citations
21. 21*

    Free Energy of a Heavy Quark-Antiquark Pair in a Thermal Medium from AdS/CFT

    Carlo Ewerz🇩🇪 · Olaf Kaczmarek🇩🇪 · Andreas Samberg🇩🇪

    We study the free energy of a heavy quark-antiquark pair in a thermal medium using the AdS/CFT correspondence. We point out that a commonly used prescription for calculating this quantity leads to a temperature dependence in conflict with general properties of the free energy. The problem originates from a particular way of subtracting divergences. We argue that the commonly used prescription gives rise to the binding energy rather than the free energy. We consider a different subtraction procedure and show that the resulting free energy is well-behaved and in qualitative agreement with results from lattice QCD. The free energy and the binding energy of the quark pair are computed for N = 4 supersymmetric Yang-Mills theory and several non-conformal theories. We also calculate the entropy and the internal energy of the pair in these theories. Using the consistent subtraction, we further study the free energy, entropy, and internal energy of a single heavy quark in the thermal medium for various theories. Also here the results are found to be in qualitative agreement with lattice QCD results.

    ↳ hep-thhep-lathep-phJHEP(2018)·40 citations
22. 22*

    Quark confinement potential examined by excitation energy of the Lambda_c and Lambda_b baryons in a quark-diquark model

    Daisuke Jido🇯🇵 · Minori Sakashita🇯🇵

    The possibility to have diquark configuration in heavy baryons, such as Lambda_c and Lambda_b, is examined by a nonrelativistic potential model with a heavy quark and a light scalar diquark. Assuming that the Lambda_c and Lambda_b baryons are composed of the heavy quark and the point-like scalar-isoscalar ud diquark, we solve the two-body Schrodinger equation with the Coulomb plus linear potential and obtain the energy spectra for the heavy baryons. Contrary to our expectation, it is found that the potential determined by the quarkonium spectra fails to reproduce the excitation spectra of the Lambda_c and Lambda_b in the quark-diquark picture, while the Lambda_c and Lambda_b spectra is reproduced with a half strength of the confinement string tension than for the quarkonium. The finite size effect of the diquark is also examined and it is found that introduction of a finite size diquark would resolve the failure of the spectrum reproduction. The Xi_c excitation energy is also calculated and is found to be smaller than Lambda_c in the quark-diquark model. This is not consistent with the experimental observation.

    ↳ nucl-thhep-phPTEP(2016)·17 citations
23. 23*

    Scale Invariance at low accelerations (aka MOND) and the dynamical anomalies in the Universe

    Mordehai Milgrom🇮🇱

    Galactic systems, and the Universe at large, exhibit large dynamical anomalies: The observed matter in them falls very short of providing enough gravity to account for their dynamics. The mainstream response to this conundrum is to invoke large quantities of `dark matter' -- which purportedly supplies the needed extra gravity -- and also of `dark energy', to account for further anomalies in cosmology, such as the observed, accelerated expansion. The MOND paradigm offers a different solution: a breakdown of standard dynamics (gravity and/or inertia) in the limit of low accelerations -- below some acceleration $a_0$. In this limit, dynamics become space-time scale invariant, and is controlled by a gravitational constant ${\mathcal{A}}_0\equiv G{a}_0$, which replaces Newton's $G$. With the new dynamics, the various detailed manifestations of the anomalies in galaxies are predicted with no need for dark matter. The cosmological anomalies could, but need not have to do with small accelerations. For example, the need for dark matter in accounting for the expansion history of the Universe is eliminated if the relevant gravitational constant is $\approx 2\pi G$. Such a `renormalization' of $G$ could be a dimensionless parameter of a MOND theory. The constant $a_0$ turns out to carry cosmological connotations, in that $2\pi a_0\approx c{H}_0\approx c^2(\Lambda /3{)}^{1/2}$, where $H_0$ is the present expansion rate of the Universe, and $\Lambda$ the measured `cosmological constant'. There are MOND theories in which this `coincidence' is natural. I draw on enlightening historical and conceptual analogies from quantum theory to limelight aspects of MOND. I also explain how MOND may have strong connections with effects of the quantum vacuum on local dynamics.

    ↳ astro-ph.GAastro-ph.COgr-qchep-phFortsch.Phys.(2017)·6 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.