Tue·Dec 29, 2015Tuesday·December 29, 2015

1. 01*

   Surprisingly large uncertainties in temperature extraction from thermal fits to hadron yield data at LHC

   Volodymyr Vovchenko🇩🇪 · Horst Stoecker🇩🇪

   The conventional hadron-resonance gas (HRG) model with the Particle Data Group (PDG) hadron input, full chemical equilibrium, and the hadron type dependent eigenvolume interactions is employed to fit the hadron mid-rapidity yield data of ALICE Collaboration for the most central Pb+Pb collisions. For the case of point-like hadrons the well-known fit result $T=154\pm 2$ MeV is reproduced. However, the situation changes if hadrons have different eigenvolumes. In the case when all mesons are point-like while all baryons have an effective hard-core radius of 0.3 fm the ${\chi }^2$ temperature dependence of the ${\chi }^2$ has a broad minimum in the temperature range of $155-210$ MeV, with fit quality comparable to the $T\sim 155$ MeV minimum in the point-particle case. Very similar result is obtained when only baryon-baryon eigenvolume interactions are considered, with eigenvolume parameter taken from previous fit to ground state of nuclear matter. Finally, when we apply the eigenvolume corrections with mass-proportional eigenvolume $v_i\sim m_i$, fixed to particular proton hard-core radius $r_p$, we observe a second minimum in the temperature dependence of the ${\chi }^2$, located at the significantly higher temperatures. For instance, at $r_p=0.5$ fm the fit quality is better than in the point-particle HRG case in a very wide temperature range of $170-320$ MeV, which gives an uncertainty in the temperature determination from the fit to the data of 150 MeV. These results show that thermal fits to the heavy-ion hadron yield data are very sensitive to the modeling of the short-range repulsion eigenvolume between hadrons, and that chemical freeze-out temperature can be extracted from the LHC hadron yield data only with sizable uncertainty.

   hep-phhep-exhep-latnucl-ex+1J.Phys.G(2017)·47 citations
2. 02*

   Basic oscillation measurables in the neutrino pair beam

   T. Asaka🇯🇵 · M. Tanaka🇯🇵 · M. Yoshimura🇯🇵

   It is shown that the vector current contribution of neutrino interaction with electrons in ion gives rise to oscillating component, which is absent for the axial-vector contribution, when a single neutrino is detected in the recently proposed neutrino pair beam. CP violation measurements are thus possible with high precision along with determination of mass hierarchical patterns.

   hep-phhep-exPLB(2016)·2 citations
3. 03*

   The $J/\psi$ production in PbPb ultraperipheral collisions at $\sqrt{s_{NN}}=2.76\mathrm{TeV}$

   Ya-ping Xie🇨🇳 · Xurong Chen🇨🇳

   We calculate the coherent and incoherent production of $J/\psi$ in PbPb ultraperipheral collisions. The production of $J/\psi$ in ultraperipheral collsions is product of photon flux distributions and cross section of photon-nucleus scatterings. The distributions of photon flux is computed in light-cone perturbation theory and the cross section of photon-nucleus scatterings is calculated in dipole model, we assume that the two gluons exchange contribution is the coherent cross section and the large-$N_c$ contribution is the incoherent cross section in photon-nucleus scattering. The numerical result of the rapidity distributions of $J/\psi$ production in PbPb ultraperipheral collisions at $\sqrt{s_{NN}}=2.76$TeV are compared with the experimental data measured by the ALICE collaboration.

   hep-phNPA(2017)·6 citations
4. 04*

   Origins of the di-jet asymmetry in heavy ion collisions

   José Guilherme Milhano🇵🇹 · Korinna Christine Zapp🇨🇭

   The di-jet asymmetry --- the measure of the momentum imbalance in a di-jet system --- is a key jet quenching observable. Using the event generator \jewel we show that the di-jet asymmetry is dominated by fluctuations both in proton-proton and in heavy ion collisions. We discuss how in proton-proton collisions the asymmetry is generated through recoil and out-of-cone radiation. In heavy ion collisions two additional sources contribute to the asymmetry, namely energy loss fluctuations and differences in path length. The latter is shown to be a sub-leading effect. We discuss the implications of our results for the interpretation of this observable.

   hep-phnucl-exnucl-thEPJC(2016)·130 citations
5. 05*

   Indirect signature of dark matter with the diphoton resonance at 750 GeV

   Jong-Chul Park🇰🇷 · Seong Chan Park🇰🇷

   Motivated by the recently reported diphoton resonance at 750 GeV, we study a new axion-like bosonic portal model of dark matter physics. When the resonance particle is identified as the pseudo-scalar mediator, via which the standard model sector would interact with the dark matter sector, the data from collider physics would provide profound implications to dark matter phenomenology. In this paper, we first identify the preferred parameter space of the suggested portal model from the results of the LHC run with $\sqrt{s}=13$ TeV, and then we examine the dark matter signature taking into account the data from cosmic-ray experiments including Fermi-LAT dwarf galaxy $\gamma$-ray search, HESS $\gamma$-line search, and future CTA diffuse $\gamma$-ray and $\gamma$-line searches.

   hep-phhep-exPhys.Dark Univ.(2016)·74 citations
6. 06*

   Elliptically Oscillating Classical Solution in Higgs Potential and the Effects on Vacuum Transitions

   Yoshio Kitadono🇹🇼 · Tomohiro Inagaki🇯🇵

   We investigate oscillating solutions of the equation of motion for the Higgs potential. The solutions are described by Jacobian elliptic functions. Classifying the classical solutions, we evaluate a possible parameter-space for the initial conditions. In order to construct the field theory around the oscillating solutions quantum fluctuations are introduced. This alternative perturbation method is useful to describe the non-trivial quantum theory around the oscillating state. This perturbation theory reduces to the standard one if we take the solution at the vacuum expectation value. It is shown that the transition probability between the vacuum and multi-quanta states is finite as long as the initial field configuration does not start from the true vacuum.

   hep-phPRD(2016)·4 citations
7. 07*

   Momentum Imbalance Observables as a Probe of Gluon TMDs

   Cristian Pisano🇧🇪

   The unpolarized and linearly polarized gluon TMDs can be directly probed in heavy quark and jet pair production in unpolarized electron-proton collisions by looking at observables, like transverse momentum distributions and azimuthal asymmetries, depending on the momentum imbalance of the pair. Analytical expressions are presented for these observables and for analogous ones in Higgs plus jet and quarkonium plus photon production in unpolarized proton-proton scattering experiments. It is shown how the proposed measurements, to be performed at a future EIC and at the LHC, could provide important information on the size and shape of gluon TMDs, as well as on other fundamental properties such as their process and energy scale dependences.

   hep-phPoS(2015)·2 citations
8. 08*

   A hidden-charm $S=-1$ pentaquark from the decay of ${\Lambda }_b$ into $J/\psi \eta \Lambda$

   A. Feijoo🇪🇸 · V.K. Magas🇪🇸 · A. Ramos🇪🇸 · E. Oset🇪🇸

   The hidden charm pentaquark state $P_c(4450)$ observed recently by the LHCb collaboration may be of molecular nature, as advocated by some unitary approaches that also predict pentaquark partners in the strangeness $S=-1$ sector. In this work we argue that a hidden-charm strange pentaquark could be seen from the decay of the ${\Lambda }_b$, just as in the case of the non-strange $P_c(4450)$, but looking into the $J/\psi \eta \Lambda$ decay mode and forming the invariant mass spectrum of $J/\psi \Lambda$ pairs. In the model presented here, which assumes a standard weak decay topology and incorporates the hadronization process and final state interaction effects, we find the $J/\psi \eta \Lambda$ final states to be populated with similar strength as the $J/\psi K^{-}p$ states employed for the observation of the non-strange pentaquark. This makes the ${\Lambda }_b\to J/\psi \eta \Lambda$ decay to be an interesting process to observe a possible strange partner of the $P_c(4450)$ . We study the dependence of the $J/\psi \Lambda$ mass spectra on various model ingredients and on the unknown properties of the strange pentaquark.

   hep-phEPJC(2016)·82 citations
9. 09*

   Spin Physics through QCD Instantons

   Yachao Qian🇺🇸 · Ismail Zahed🇺🇸

   We review some aspects of spin physics where QCD instantons play an important role. In particular, their large contributions in semi-inclusive deep-inelastic scattering and polarized proton on proton scattering. We also review their possible contribution in the $\mathcal{P}$-odd pion azimuthal charge correlations in peripheral $AA$ scattering at collider energies.

   hep-phnucl-thAnnals Phys.(2016)·13 citations
10. 10*

    Renormalization Scheme Dependence in a QCD Cross Section

    Farrukh Chishtie🇵🇰 · D.G.C. McKeon🇨🇦 · T.N. Sherry🇮🇪

    The zero to four loop contribution to the cross section $R_{e^{+}{e}^{-}}$ for $e^{+}{e}^{-}⟶$ hadrons, when combined with the renormalization group equation, allows for summation of all leading-log ($LL$), next-to-leading-log $(NLL)\dots N^{3}LL$ perturbative contributions. It is also shown how all logarithmic contributions to $R_{e^{+}{e}^{-}}$ can be summed and that $R_{e^{+}{e}^{-}}$ can be expressed in terms of the log independent contributions, and once this is done the running coupling $a$ is evaluated at a point independent of the renormalization scale $\mu$. All explicit dependence of $R_{e^{+}{e}^{-}}$ on $\mu$ cancels against its implicit dependence on $\mu$ through the running coupling $a$ so that the ambiguity associated with the value of $\mu$ is shown to disappear. The renormalization scheme dependency of the "summed" cross section $R_{e^{+}{e}^{-}}$ is examined in three distinct renormalization schemes. In each case, $R_{e^{+}{e}^{-}}$ is expressible in terms of renormalization scheme independent parameters ${\tau }_i$ and is explicitly and implicitly independent of the renormalization scale $\mu$. Two of the forms are then compared graphically both with each other and with the purely perturbative results and the $RG$-summed $N^{3}LL$ results.

    hep-phPRD(2016)·21 citations
11. 11*

    Can Dark Matter be an artifact of extended theories of gravity?

    Sayantan Choudhury🇮🇳 · Manibrata Sen🇮🇳 · Soumya Sadhukhan🇮🇳

    In this article, we propose different background models of extended theories of gravity, which are minimally coupled to the SM fields, to explain the possibility of genesis of dark matter without affecting the SM particle sector. We modify the gravity sector by allowing quantum corrections motivated from (1) local $f(R)$ gravity and (2) non-minimally coupled gravity with SM sector and dilaton field. Next we apply conformal transformation on the metric to transform the action back to the Einstein frame. We also show that an effective theory constructed from these extended theories of gravity and SM sector looks exactly the same. Using the relic constraint observed by Planck 2015, we constrain the scale of the effective field theory (${\Lambda }_{UV}$) as well as the dark matter mass ($M$). We consider two cases- (1) light dark matter (LDM) and (2) heavy dark matter (HDM), and deduce upper bounds on thermally averaged cross section of dark matter annihilating to SM particles. Further we show that our model naturally incorporates self interactions of dark matter. Using these self interactions, we derive the constraints on the parameters of the (1) local $f(R)$ gravity and (2) non-minimally coupled gravity from dark matter self interaction. Finally, we propose some different UV complete models from a particle physics point of view, which can give rise to the same effective theory that we have deduced from extended theories of gravity.

    hep-phastro-ph.COgr-qchep-thEPJC(2016)·26 citations
12. 12*

    Higgs Stability and the 750 GeV Diphoton Excess

    Alberto Salvio🇨🇭 · Anupam Mazumdar🇬🇧

    We study the implications of a possible unstable particle with mass $M_X<$ TeV for the Higgs stability, naturalness and inflation. We pay particular attention to the case $M_X\approx$ 750 GeV, suggested by recent results of ATLAS and CMS on diphoton final states, and work within the minimal model: we add to the Standard Model field content a pseudoscalar and a vector-like fermion carrying both color and electric charge. This can stabilize the electroweak vacuum without invoking new physics at very high energies, which would give an unnaturally large contribution to the Higgs mass. We also show that inflation can be obtained via a UV modification of General Relativity.

    hep-phPLB(2016)·101 citations
13. 13*

    Glue to light signal of a new particle

    Dongjin Chway🇰🇷 · Radovan Dermisek🇺🇸 · Tae Hyun Jung🇰🇷 · Hyung Do Kim🇰🇷

    Any new particle charged under $SU(3{)}_C$ and carrying electric charge will leave an imprint in the di-photon invariant mass spectrum as it can mediate $gg\to \gamma \gamma$ process through loops. The combination of properties of loop functions, threshold resummation and gluon pdfs can result in a peak-like feature in the di-photon invariant mass around twice the mass of a given particle even if the particle is short-lived and thus it doesn't form a narrow bound state. Using recent ATLAS analysis, we set upper limits on the combined $SU(3{)}_C$ and electric charge of new particles and indicate future prospects. We also discuss the possibility that the excess of events in the di-photon invariant mass spectrum around 750 GeV originates from loops of a particle with mass around 375 GeV.

    hep-phhep-exPRL(2016)·50 citations
14. 14*

    Strange matter and strange stars in a thermodynamically self-consistent perturbation model with running coupling and running strange quark mass

    J. F. Xu🇨🇳 · G. X. Peng🇨🇳 · F. Liu🇨🇳 · D. F. Hou🇨🇳 · L. W. Chen🇨🇳

    A quark model with running coupling and running strange quark mass, which is thermodynamically self-consistent at both high and lower densities, is presented and applied to study properties of strange quark matter and structure of compact stars. An additional term to the thermodynamic potential density is determined by meeting the fundamental differential equation of thermodynamics. It plays an important role in comparatively lower density and ignorable at extremely high density, acting as a chemical-potential dependent bag constant. In this thermodynamically enhanced perturbative QCD model, strange quark matter still has the possibility of being absolutely stable, while the pure quark star has a sharp surface with a maximum mass as large as about 2 times the solar mass and a maximum radius of about 11 kilometers.

    hep-phastro-ph.SRnucl-thPRD(2015)·48 citations
15. 15*

    Entropic destruction of a moving heavy quarkonium

    Kazem Bitaghsir Fadafan🇮🇷 · Seyed Kamal Tabatabaei🇮🇷

    Recently it has been shown that the peak of the quarkonium entropy at the deconfinement transition is related to the emergent entropic force which destructs the quarkonium. Using the AdS/CFT correspondence, we consider dissociation of a moving heavy quarkonium by entropic force. We find that the entropic force destructs the moving quarkonium easier than the static case which is expected from perturbative weakly coupled plasma. By considering the Maxwell charge, we study the effect of medium on the destruction of heavy quarkonium. It is shown that the quarkonium dissociates easier in the medium.

    hep-phhep-lathep-thnucl-thPRD(2016)·38 citations
16. 16*

    A Loop-philic Pseudoscalar

    Gang Li🇨🇳 · Ying-nan Mao🇨🇳 · Yi-Lei Tang🇨🇳 · Chen Zhang🇨🇳 · Yang Zhou🇨🇳 · Shou-hua Zhu🇨🇳

    We construct a weakly-coupled renormalizable model to explain the $750\text{mbox}GeV$ diphoton excess. The $750\text{mbox}GeV$ resonance (denoted as $X(750)$) is interpreted as a pseudoscalar coming from a complex singlet. The model also naturally provides a dark matter candidate. One most attractive feature of the model is that decays of $X(750)$ are all loop-induced so the diphoton rate is not diluted by unwanted tree level branching fractions. Relevant Yukawa interactions need not to be tuned to near non-perturbative region to explain the rate. The model is highly predictive, including the pseudoscalar nature of $X(750)$, and two nearly mass-degenerate exotic quarks carrying electric charge $5/3$ and $2/3$, respectively. Rich phenomenology is expected with respect to collider searches, flavor physics and dark matter detection, if $X(750)$ can be pinned down by future LHC experiments.

    hep-phPRL(2016)·75 citations
17. 17*

    High order QCD predictions for inclusive production of $W$ bosons in $pp$ collisions at $\sqrt{s}$$=13$ TeV

    Hasan Ogul🇺🇸 · Kamuran Dilsiz🇺🇸 · Emrah Tiras🇺🇸 · Ping Tan🇺🇸 · Yasar Onel🇺🇸 · Jane Nachtman🇺🇸

    Predictions of fiducial cross sections, differential cross sections and lepton charge asymmetry are presented for the production of $W^{\pm }$ bosons with leptonic decay up to next-to-next-to-leading order (NNLO) in perturbative QCD. Differential cross sections of $W^{\pm }$ bosons and W boson lepton charge asymmetry are computed as a function of lepton pseudorapidity for a defined fiducial region in $pp$ collisions at $\sqrt{s}=13$ TeV. Numerical results of fiducial $W^{\pm }$ cross section predictions are presented with the latest modern PDF models at next-to-leading order (NLO) and NNLO. It is found that the CT14 and NNPDF 3.0 predictions with NNLO QCD corrections are about 4$\%$ higher than the NLO CT14 and NNPDF 3.0 predictions while MMHT 2014 predictions with NLO QCD corrections are smaller than its NNLO QCD predictions by approximately 6$\%$. In addition, the NNLO QCD corrections reduce the scale variation uncertainty on the cross section by a factor of 3.5. The prediction of central values and considered uncertainties are obtained using FEWZ 3.1 program.

    hep-phhep-exAdv.High Energy Phys.(2016)·11 citations
18. 18*

    A new scalar resonance at 750 GeV: Towards a proof of concept in favor of strongly interacting theories

    Minho Son🇰🇷 · Alfredo Urbano🇨🇭

    We interpret the recently observed excess in diphoton invariant mass as a new spin-0 resonant particle. On the theoretical ground, an interesting question is whether this new scalar resonance belongs to a strongly coupled sector or a well-defined weakly coupled theory. A possible UV-completion that has been widely considered in literature is based on the existence of new vector-like fermions whose loop contributions---Yukawa-coupled to the new resonance---explain the observed signal rate. The large total width preliminarily suggested by data seems to favor a large Yukawa coupling, at the border of a healthy perturbative definition. This potential problem can be fixed by introducing multiple vector-like fermions or large electric charges, bringing back the theory to a weakly coupled regime. However, this solution risks to be only a low-energy mirage: Large multiplicity or electric charge can dangerously reintroduce the strong regime by modifying the renormalization group running of the dimensionless couplings. This issue is also tightly related to the (in)stability of the scalar potential. First, we study---in the theoretical setup described above---the parametric behavior of the diphoton signal rate, total width, and one-loop $\beta$ functions. Then, we numerically solve the renormalization group equations, taking into account the observed diphoton signal rate and total width, to investigate the fate of the weakly coupled theory. We find that---with the only exception of few fine-tuned directions---weakly coupled interpretations of the excess are brought back to a strongly coupled regime if the running is taken into account.

    hep-phJHEP(2016)·101 citations
19. 19*

    NMSSM extended with vectorlike particles and the diphoton excess at the LHC

    Yi-Lei Tang🇨🇳 · Shou-hua Zhu🇨🇳

    We investigate the parameter space of a model which extends next to minimal supersymmetric standard model (NMSSM) with the vectorlike (VL) particles. We find that the $10+\overline{10}$ model can explain the possible diphoton excess recently revealed by the ATLAS and CMS collaborations, although the predicted signal strength is a little smaller than the observed one.

    hep-phPRD(2016)·81 citations
20. 20*

    New Avenues to Heavy Right-handed Neutrinos with Pair Production at Hadronic Colliders

    Zhaofeng Kang🇰🇷 · P. Ko🇰🇷 · Jinmian Li🇦🇺

    In many models incorporating the type-I seesaw mechanism, the right-handed neutrino ($N$) couples to heavy vector/scalar bosons and thereby has resonant pair production. It barely receives attention thus far, however, it may provide the best avenue to probe TeV scale $N$ without requiring anomalously large mixing between $N$ and the active neutrino ${\nu }_L$. In this paper we explore the discovery prospects of (mainly heavy) $N$ pair production at the 14 TeV LHC and future 100 TeV $pp$ collider, based on the three signatures: 1) trilepton from $N(\to \ell W_{\ell })N(\to \ell W_h)$ with $W_{\ell /h}$ the leptonically/hadronically decaying $W$; 2) boosted di-Higgs boson plus MET from $N(\to {\nu }_{L}h)N(\to {\nu }_{L}h)$; 3) a single boosted Higgs with leptons and MET from $N(\to \ell W_{\ell })N(\to {\nu }_{L}h)$. At the 100 TeV collider, we also consider the situation when the Higgs boson is over boosted thus losing its jet substructure. Interpreting our tentative results in the benchmark model, the local $B-L$ model, we find that the (multi-) TeV scale $N$ can be probed at the (100) 14 TeV colliders.

    hep-phhep-exPRD(2016)·64 citations
21. 21*

    Non-dipolar gauge links for transverse-momentum-dependent pion wave functions

    Yu-Ming Wang🇦🇹

    I discuss the factorization-compatible definitions of transverse-momentum-dependent (TMD) pion wave functions which are fundamental theory inputs entering QCD factorization formulae for many hard exclusive processes. I will first demonstrate that the soft subtraction factor introduced to remove both rapidity and pinch singularities can be greatly reduced by making the maximal use of the freedom to construct the Wilson-line paths when defining the TMD wave functions. I will then turn to show that the newly proposed TMD definition with non-dipolar Wilson lines is equivalent to the one with dipolar gauge links and with a complicated soft function, to all orders of the perturbative expansion in the strong coupling, as far as the infrared behavior is concerned.

    hep-phEPJ Web Conf.(2016)·7 citations
22. 22*

    Broad Diphotons from Narrow States

    Haipeng An🇺🇸 · Clifford Cheung🇺🇸 · Yue Zhang🇺🇸

    ATLAS and CMS have each reported a modest diphoton excess consistent with the decay of a broad resonance at ~ 750 GeV. We show how this signal can arise in a weakly coupled theory comprised solely of narrow width particles. In particular, if the decaying particle is produced off-shell, then the associated diphoton resonance will have a broad, adjustable width. We present simplified models which explain the diphoton excess through the three-body decay of a scalar or fermion. Our minimal ultraviolet completion is a weakly coupled and renormalizable theory of a singlet scalar plus a heavy vector-like quark and lepton. The smoking gun of this mechanism is an asymmetric diphoton peak recoiling against missing transverse energy, jets, or leptons.

    hep-phhep-ex72 citations
23. 23*

    Quark and Lepton Mass Matrices Described by Charged Lepton Masses

    Yoshio Koide🇯🇵 · Hiroyuki Nishiura🇯🇵

    Recently, we proposed a unified mass matrix model for quarks and leptons, in which, mass ratios and mixings of the quarks and neutrinos are described by using only the observed charged lepton mass values as family-number-dependent parameters and only six family-number-independent free parameters. In spite of quite few parameters, the model gives remarkable agreement with observed data (i.e. CKM mixing, PMNS mixing and mass ratios). Taking this phenomenological success seriously, we give a formulation of the so-called Yukawaon model in details from a theoretical aspect, especially for the construction of superpotentials and $R$ charge assignments of fields. The model is considerably modified from the previous one, while the phenomenological success is kept unchanged.

    hep-phMod.Phys.Lett.A(2016)·5 citations
24. 24*

    Heavy ion collisions and cosmology

    Stefan Floerchinger🇩🇪

    There are interesting parallels between the physics of heavy ion collisions and cosmology. Both systems are out-of-equilibrium and relativistic fluid dynamics plays an important role for their theoretical description. From a comparison one can draw interesting conclusions for both sides. For heavy ion physics it could be rewarding to attempt a theoretical description of fluid perturbations similar to cosmological perturbation theory. In the context of late time cosmology, it could be interesting to study dissipative properties such as shear and bulk viscosity and corresponding relaxation times in more detail. Knowledge and experience from heavy ion physics could help to constrain the microscopic properties of dark matter from observational knowledge of the cosmological fluid properties.

    hep-phnucl-thNPA(2016)·4 citations
25. 25*

    Interpreting The 750 GeV Diphoton Excess Within Topflavor Seesaw Model

    Junjie Cao🇨🇳 · Liangliang Shang🇨🇳 · Wei Su🇨🇳 · Fei Wang🇨🇳 · Yang Zhang🇨🇳

    We propose to interpret the 750 GeV diphoton excess in a typical topflavor seesaw model. The new resonance X can be identified as a CP-even scalar emerging from a certain bi-doublet Higgs field. Such a scalar can couple to charged scalars, fermions as well as heavy gauge bosons predicted by the model, and consequently all of the particles contribute to the diphoton decay mode of the X. Numerical analysis indicates that the model can predict the central value of the diphoton excess without contradicting any constraints from 8 TeV LHC, and among the constraints, the tightest one comes from the Z \gamma channel, \sigma_{8 {\rm TeV}}^{Z \gamma} \lesssim 3.6 {\rm fb}, which requires \sigma_{13 {\rm TeV}}^{\gamma \gamma} \lesssim 6 {\rm fb} in most of the favored parameter space.

    hep-phNPB(2016)·77 citations
26. 26*

    Probing degenerate heavy Higgs bosons in NMSSM with vector-like particles

    Fei Wang🇨🇳 · Wenyu Wang🇨🇳 · Lei Wu🇦🇺 · Jin Min Yang🇨🇳 · Mengchao Zhang🇨🇳

    In this work, we investigate the degenerate heavy Higgs bosons in the Next-to-Minimal Supersymmetric Standard Model (NMSSM) by introducing vector-like particles. Such an extension is well motivated from the top-down view since some grand unified theories usually predict the existence of singlet scalars and vector-like particles at weak scale. Under the constraints from the LHC and dark matter experiments, we find that (1) the null results of searching for high mass resonances have tightly constrained the parameter space; (2) two degenerate heavy singlet Higgs bosons $h_2$ and $a_1$ can sizably decay to ${\chi }_1^0{\chi }_1^0$ invisibly. Therefore, search for the monojet events through the process $gg\to h_2/a_1(\to {\chi }_1^0{\chi }_1^0)j$ may further test our scenario at the future LHC.

    hep-phhep-exInt.J.Mod.Phys.A(2017)·109 citations
27. 27*

    The 750 GeV diphoton resonance as a singlet scalar in an extra dimensional model

    Chengfeng Cai🇨🇳 · Zhao-Huan Yu🇦🇺 · Hong-Hao Zhang🇨🇳

    We interpret the 750~GeV diphoton excess recently found in the 13~TeV LHC data as a singlet scalar in an extra dimensional model, where one extra dimension is introduced. In the model, the scalar couples to multiple vector-like fermions, which are just the KK modes of SM fermions. Mediated by the loops of these vector-like fermions, the $\varphi$ effective couplings to gluons and photons can be significantly large. Therefore, it is quite easy to obtain an observed cross section for the diphoton excess. We also calculate the cross sections for other decay channels of $\varphi$, and find that this interpretation can evade the bounds from the 8~TeV LHC data.

    hep-phPRD(2016)·87 citations
28. 28*

    The Diphoton Excess, Low Energy Theorem and the 331 Model

    Qing-Hong Cao🇨🇳 · Yandong Liu🇨🇳 · Ke-Pan Xie🇨🇳 · Bin Yan🇨🇳 · Dong-Ming Zhang🇨🇳

    We interpret the diphoton anomaly as a heavy scalar $H_3$ in the so-called 331 model. The scalar is responsible for breaking the $SU(3{)}_C\otimes SU(3{)}_L\otimes U(1{)}_X$ gauge symmetry down to the standard model electroweak gauge group. It mainly couples to the standard model gluons and photons through quantum loops involving heavy quarks and leptons. Those quarks and leptons, in together with the SM quarks and leptons, form the fundamental representation of the 331 model. We use low energy theorem to calculate effective coupling of $H_{3}gg$, $H_3\gamma \gamma$, $H_{3}ZZ$, $H_{3}WW$ and $H_{3}Z\gamma$. The analytical results can be applied to new physics models satisfying the low energy theorem. We show that the heavy quark and lepton contribution cannot produce enough diphoton pairs. It is crucial to include the contribution of charged scalars to explain the diphoton excess. The extra neutral $Z^{\prime }$ boson could also explain the 2 TeV diboson excess observed at the LHC Run-I.

    hep-phhep-exPRD(2016)·106 citations
29. 29*

    The Polyakov loop at next-to-next-to leading order

    Matthias Berwein🇩🇪 · Nora Brambilla🇩🇪 · Peter Petreczky🇺🇸 · Antonio Vairo🇩🇪

    We calculate the next-to-next-to-leading correction to the expectation value of the Polyakov loop or equivalently to the free energy of a static charge. This correction is of order $g^5$. We show that up to this order the free energy of the static charge is proportional to the quadratic Casimir operator of the corresponding representation. We also compare our perturbative result with the most recent lattice results in SU(3) gauge theory.

    hep-phhep-lathep-thnucl-thPRD(2016)·27 citations
30. 30*

    Correlating the skewness and kurtosis of baryon number distributions

    Wei-jie Fu🇩🇪 · Jan M. Pawlowski🇩🇪

    The skewness and the kurtosis of the baryon number distributions are computed within QCD-improved low energy effective models including quantum thermal and density fluctuations. The results are compared with the Beam Energy Scan experiment at RHIC. The theoretical results agree with the experimental measurements up to errors, for the collision energy $\sqrt{s}\ge 19.6\mathrm{GeV}$. For smaller collision energies a discrepancy between theoretical and experimental results develops. This discrepancy partially relates to the lack of precision of the current setup for small collision energies. It is outlined how this deficiency can be overcome.

    hep-phPRD(2016)·38 citations
31. 31*

    Is an axizilla possible for di-photon resonance?

    Jihn E. Kim🇰🇷

    Heavy axion-like particles, called axizillas, are simple extensions of the standard model(SM). An axizilla is required not to couple to the quarks, leptons, and Brout-Englert-Higgs doublets of the SM, but couple to the gauge anomalies of the $W^{\pm },Z$ and photon. It is possible to have its branching ratios(BRs) to two photons greater than 10% and to two $Z$'s less than 10%. To have a (production cross section)$\cdot$(BR to di-photons) at a $10^{-38}{\text{cm}}^2$ level, a TeV scale heavy quark $Q$ is required for the gluon--quark fusion process. The decay of $Q$ to axizilla plus quark, and the subsequent decay of the axizilla to two photons can be fitted at the required level of $10^{-38}{\text{cm}}^2$.

    hep-phPLB(2016)·60 citations
32. 32*

    Diphoton excess at 750 GeV: gluon-gluon fusion or quark-antiquark annihilation?

    Jun Gao🇺🇸 · Hao Zhang🇺🇸 · Hua Xing Zhu🇺🇸

    Recently, ATLAS and CMS collaboration reported an excess in the diphoton events, which can be explained by a new resonance with mass around 750 GeV. In this work, we explored the possibility of identifying if the hypothetical new resonance is produced through gluon-gluon fusion or quark-antiquark annihilation, or tagging the beam. Three different observables for beam tagging, namely the rapidity and transverse momentum distribution of the diphoton, and one tagged bottom-jet cross section, are proposed. Combining the information gained from these observables, a clear distinction of the production mechanism for the diphoton resonance is promising.

    hep-phhep-exEPJC(2016)·79 citations
33. 33*

    Cool WISPs for stellar cooling excesses

    Maurizio Giannotti🇺🇸 · Igor Irastorza🇪🇸 · Javier Redondo🇪🇸 · Andreas Ringwald🇩🇪

    Several stellar systems (white dwarfs, red giants, horizontal branch stars and possibly the neutron star in the supernova remnant Cassiopeia A) show a mild preference for a non-standard cooling mechanism when compared with theoretical models. This exotic cooling could be provided by Weakly Interacting Slim Particles (WISPs), produced in the hot cores and abandoning the star unimpeded, contributing directly to the energy loss. Taken individually, these excesses do not show a strong statistical weight. However, if one mechanism could consistently explain several of them, the hint could be significant. We analyze the hints in terms of neutrino anomalous magnetic moments, minicharged particles, hidden photons and axion-like particles (ALPs). Among them, the ALP or a massless HP represent the best solution. Interestingly, the hinted ALP parameter space is accessible to the next generation proposed ALP searches, such as ALPS II and IAXO and the massless HP requires a multi TeV energy scale of new physics that might be accessible at the LHC.

    ↳ astro-ph.HEastro-ph.SRhep-phJCAP(2016)·224 citations
34. 34*

    Classical and Quantum Stability in Putative Landscapes

    Michael Dine🇺🇸

    Landscape analyses often assume the existence of large numbers of fields, $N$, with all of the many couplings among these fields (subject to constraints such as local supersymmetry) selected independently and randomly from simple (say Gaussian) distributions. We point out that unitarity and perturbativity place significant constraints on behavior of couplings with $N$, eliminating otherwise puzzling results. In would-be flux compactifications of string theory, we point out that in order that there be large numbers of light fields, the compactification radii must scale as a positive power of $N$; scaling of the radii and couplings with $N$ may also be necessary for perturbativity. We show that in some simple string theory settings with large numbers of fields, for fixed $R$ and string coupling, one can bound certain sums of squares of couplings by order one numbers. This may argue for strong correlations, possibly calling into question the assumption of random distributions. We consider implications of these considerations for classical and quantum stability of states without supersymmetry, with low energy supersymmetry arising from tuning of parameters, and with dynamical breaking of supersymmetry.

    ↳ hep-thhep-phJHEP(2017)·11 citations
35. 35*

    Effective QCD and transport description of dilepton and photon production in heavy-ion collisions and elementary processes

    O. Linnyk🇩🇪 · E. L. Bratkovskaya🇩🇪 · W. Cassing🇩🇪

    In this review we address the dynamics of relativistic heavy-ion reactions and in particular the information obtained from electromagnetic probes that stem from the partonic and hadronic phases. The out-of-equilibrium description of strongly interacting relativistic fields is based on the theory of Kadanoff and Baym. For the modeling of the partonic phase we introduce a dynamical quasiparticle model (DQPM) for QCD in equilibrium. The widths and masses of the quasiparticles are controlled by transport coefficients in comparison to lattice QCD results. The resulting off-shell transport approach - denoted by Parton-Hadron-String Dynamics (PHSD) - also includes covariant dynamical hadronization and keeps track of the hadronic interactions in the final phase. We show that PHSD captures the bulk dynamics of heavy-ion collisions from SPS to LHC energies and provides a basis for the evaluation of the electromagnetic emissivity, using the same dynamical parton propagators as for the system evolution. Direct photon production in elementary processes and heavy-ion reactions at RHIC and LHC energies is investigated and the status of the photon v2 puzzle - a large elliptic flow of the direct photons observed in A+A collisions - is addressed. We discuss the roles of hadronic and partonic sources for the photon spectra and the flow coefficients v2 and v3 and also the possibility to subtract the QGP signal from observables. Furthermore, the production of dilepton pairs is addressed from SIS to LHC energies. The low-mass dilepton yield is enhanced due to the in-medium modification of the rho-meson and at the lowest energy also due to a multiple regeneration of Delta-resonances. In addition, a signal of the partonic degrees-of-freedom is found in the intermediate dilepton mass regime (1.2GeV<M<3GeV), which can shed light on the nature of the very early degrees-of-freedom in nucleus-nucleus collisions.

    ↳ nucl-thhep-exhep-phPPNP(2016)·174 citations
36. 36*

    A non-conventional neutrino beamline for the measurement of the electron neutrino cross section

    A. Berra🇮🇹 · S. Cecchini🇮🇹 · F. Cindolo🇮🇹 · C. Jollet🇫🇷 · A. Longhin🇮🇹 · L. Ludovici🇮🇹 · G. Mandrioli🇮🇹 · N. Mauri🇮🇹 · A. Meregaglia🇫🇷 · A. Paoloni🇮🇹 · L. Pasqualini🇮🇹 · L. Patrizii🇮🇹 and 7 other authors

    Absolute neutrino cross section measurements at the GeV scale are ultimately limited by the knowledge of the initial $\nu$ flux. In order to evade such limitation and reach the accuracy that is needed for precision oscillation physics ($\sim 1$%), substantial advances in flux measurement techniques are requested. We discuss here the possibility of instrumenting the decay tunnel to identify large-angle positrons and monitor ${\nu }_e$ production from $K^{+}\to e^{+}{\nu }_e{\pi }^0$ decays. This non conventional technique opens up opportunities to measure the ${\nu }_e$ CC cross section at the per cent level in the energy range of interest for DUNE/HK. We discuss the progress in the simulation of the facility (beamline and instrumentation) and the ongoing R&D.

    ↳ hep-exhep-phphysics.ins-det4 citations
37. 37*

    New insights from 3D simulations of heavy ion collisions

    Gabriel Denicol🇺🇸 · Akihiko Monnai🇺🇸 · Sangwook Ryu🇨🇦 · Bjoern Schenke🇺🇸

    Viscous relativistic hydrodynamics in 3+1 dimensions is applied to describe heavy ion collisions at RHIC and LHC. We present calculations of observables that are sensitive to the longitudinal structure of the created system. In particular we present pseudo-rapidity correlations and demonstrate their dependence on both the initial state and short range correlations introduced via a microscopic transport description. We further demonstrate the effect of a varying temperature dependence of the shear viscosity to entropy density ratio on rapidity dependent flow harmonics.

    ↳ nucl-thhep-phnucl-exNPA(2016)·11 citations
38. 38*

    Gravitational radiation in dynamical noncommutative spaces

    S. A. Alavi🇮🇷 · M. Amiri Nasab🇮🇷

    We investigate gravitational radiation in dynamical noncommutative spaces. By including corrections to the gravitational potential due to dynamical noncommutativity, we calculate the power in gravitational radiation and use observational data to place an upper bound on the noncommutativity parameter. We also study quantum interference induced by gravitational potential in the usual and dynamical noncommutative spaces, and compare the resulting phase difference in these cases with that in commutative space.

    ↳ hep-thgr-qchep-phquant-phGen.Rel.Grav.(2017)·6 citations
39. 39*

    Remembering a Great Teacher

    Alberto Sirlin🇺🇸

    The article is a recollection of the memorable experience of attending a course on Quantum Mechanics given by Feynman in Brasil, as well as several meetings and exchanges Daniele Amati and I had with him over many years, in both the U.S. and Europe. The article also includes a small sample of the problems assigned in the course, a one-page guide, hand-written by Feynman, to study QED on the basis of two of his most important papers, and his reply to a letter of congratulations that the author had sent to him on the occasion of his Nobel Prize Award.

    ↳ physics.hist-phhep-phhep-th0 citations
40. 40*

    Precision Measurements of Electroweak Parameters with Z Bosons at the Tevatron

    Arie Bodek🇺🇸

    We report on the extraction of ${\sin }^2{\theta }_{\mathrm{eff}}^{\mathrm{lept}}(M_Z)$ and an indirect measurement of the mass of the W boson from the forward-backward asymmetry of dilepton events in the $Z$ boson mass region at the Tevatron. The data samples of $e^{+}{e}^{-}$ and ${\mu }^{+}{\mu }^{-}$ events collected by the CDF detector correspond to the full 9.4 fb${}^{-1}$ run II sample and yield an effective electroweak mixing angle ${\sin }^2{\theta }_{\mathrm{eff}}^{\mathrm{lept}}(M_Z)=0.23222\pm 0.00046$. The corresponding result reported by the D0 collaboration with the full 9.4 fb${}^{-1}$ $e^{+}e-$ sample is ${\sin }^2{\theta }_{\mathrm{eff}}^{\mathrm{lept}}(M_Z)=0.23146\pm 0.00047$. The CDF collaboration also extracts the on-shell electroweak mixing angle ${\sin }^2{\theta }_W=0.22401\pm 0.00044$ which corresponds to an indirect measurement of the W boson mass $M_W(\mathrm{indirect})=80.327\pm 0.023\mathrm{GeV}$. The quoted uncertainties include both statistical and systematic contributions.

    ↳ hep-exhep-phThe European Physical Journal C, 76(3), 1…·3 citations
41. 41*

    Pre-equilibrium dynamics and heavy-ion observables

    Ulrich W. Heinz🇺🇸 · Jia Liu (Ohio State University)🇺🇸

    To bracket the importance of the pre-equilibrium stage on relativistic heavy-ion collision observables, we compare simulations where it is modeled by either free-streaming partons or fluid dynamics. These cases implement the assumptions of extremely weak vs. extremely strong coupling in the initial collision stage. Accounting for flow generated in the pre-equilibrium stage, we study the sensitivity of radial, elliptic and triangular flow on the switching time when the hydrodynamic description becomes valid. Using the hybrid code iEBE-VISHNU we perform a multi-parameter search, constrained by particle ratios, integrated elliptic and triangular charged hadron flow, the mean transverse momenta of pions, kaons and protons, and the second moment $⟨p_T^2⟩$ of the proton transverse momentum spectrum, to identify optimized values for the switching time ${\tau }_s$ from pre-equilibrium to hydrodynamics, the specific shear viscosity $\eta /s$, the normalization factor of the temperature-dependent specific bulk viscosity $(\zeta /s)(T)$, and the switching temperature $T_{\mathrm{sw}}$ from viscous hydrodynamics to the hadron cascade UrQMD. With the optimized parameters, we predict and compare with experiment the $p_T$-distributions of $\pi$, $K$, $p$, $\Lambda$, $\Xi$ and $\Omega$ yields and their elliptic flow coefficients, focusing specifically on the mass-ordering of the elliptic flow for protons and Lambda hyperons which is incorrectly described by VISHNU without pre-equilibrium flow.

    ↳ nucl-thhep-phnucl-exNPA(2016)·27 citations
42. 42*

    Angular distribution of cosmic rays from an individual source in a turbulent magnetic field

    Diego Harari🇦🇷 · Silvia Mollerach🇦🇷 · Esteban Roulet🇦🇷

    We obtain the angular distribution of the cosmic rays reaching an observer from an individual source and after propagation through a turbulent magnetic field, for different ratios between the source distance and the diffusion length. We study both the high-energy quasi-rectilinear regime as well as the transition towards the diffusive regime at lower energies where the deflections become large. We consider the impact of energy losses, showing that they tend to enhance the anisotropy of the source at a given energy. We also discuss lensing effects, in particular those that could result from the regular galactic magnetic field component, and show that the effect of the turbulent extragalactic magnetic fields can smooth out the divergent magnification peaks that would result for point-like sources in the limit of no turbulent deflections.

    ↳ astro-ph.HEhep-phPRD(2016)·17 citations
43. 43*

    Cosmic Hysteresis

    Sayantan Choudhury🇮🇳 · Shreya Banerjee🇮🇳

    Cosmological hysteresis, has interesting and vivid implications in the scenario of a cyclic bouncy universe. This, purely thermodynamical in nature, is caused by the asymmetry in the equation of state parameter during expansion and contraction phase of the universe, due to the presence of a single scalar field. When applied to variants of modified gravity models this phenomenon leads to the increase in amplitude of the consecutive cycles of the universe, provided we have physical mechanisms to make the universe bounce and turnaround. This also shows that the conditions which creates a universe with an ever increasing expansion, depend on the signature of $\oint pdV$ and on model parameters.

    ↳ hep-thastro-ph.COgr-qchep-phThe Fourteenth Marcel Grossmann Meeting 4…·6 citations
44. 44*

    Evaluating Multiple Polylogarithm Values at Sixth Roots of Unity up to Weight Six

    Johannes M. Henn🇩🇪 · Alexander V. Smirnov🇷🇺 · Vladimir A. Smirnov🇷🇺

    We evaluate multiple polylogarithm values at sixth roots of unity up to weight six, i.e. of the form $G(a_1,\dots ,a_w;1)$ where the indices $a_i$ are equal to zero or a sixth root of unity, with $a_1\ne 1$. For $w\le 6$, we present bases of the linear spaces generated by the real and imaginary parts of $G(a_1,\dots ,a_w;1)$ and present a table for expressing them as linear combinations of the elements of the bases.

    ↳ hep-thhep-phmath-phmath.MP+1NPB(2017)·51 citations
45. 45*

    On Hermitian separability of the next-to-leading order BFKL kernel for the adjoint representation of the gauge group in the planar N = 4 SYM

    V.S. Fadin🇷🇺 · R. Fiore🇮🇹

    We analyze a modification of the BFKL kernel for the adjoint representation of the colour group in the maximally supersymmetric (N=4) Yang-Mills theory in the limit of a large number of colours, related to the modification of the eigenvalues of the kernel suggested by S. Bondarenko and A. Prygarin in order to reach the Hermitian separability of the eigenvalues. We restore the modified kernel in the momentum space. It turns out that the modification is related only to the real part of the kernel and that the correction to the kernel can not be presented by a single analytic function in the entire momentum region, which contradicts the known properties of the kernel.

    ↳ hep-thhep-phEPJC(2016)·2 citations
46. 46*

    On the possible new heavy scalar and pseudoscalar resonances at the LHC

    Davor Palle🇭🇷

    We argue that the possible new heavy boson resonance of 750 GeV is an ideal candidate as a twin particle of the 125 GeV scalar boson, both emerging from the large mixing of the scalar toponium and scalar gluonium. The twin pseudoscalar particles are expected to have smaller masses. The discovery of the 750 GeV resonance is possible only with a much more data than for the 125 GeV resonance since only the gluonium component is detectable above the toponium threshold. The similar type of the QCD resonances is expected in the bottomonium-gluonium system. If the LHC will discover all these heavy quarkonium-gluonium resonances, the absence of the Higgs scalar should not be considered an obstacle because the nonsingular theory with the UV cutoff fixed by the weak boson masses is superior to the Standard Model. Namely, it solves the basic problems for the SM such as: (1) the existence of light neutrinos, (2) dark matter particles to be the heavy Majorana neutrinos and (3) broken lepton and baryon numbers.

    ↳ physics.gen-phhep-ph28 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.