Mon·Feb 8, 2016Monday·February 8, 2016

1. 01*

   Realizing Dark Matter and Higgs Inflation in Light of LHC Diphoton Excess

   Shao-Feng Ge🇩🇪 · Hong-Jian He🇨🇳 · Jing Ren🇨🇦 · Zhong-Zhi Xianyu🇺🇸

   LHC Run-2 has provided intriguing di-photon signals of a new resonance around 750GeV, which, if not due to statistical fluctuations, must call for new physics beyond the standard model (SM) at TeV scale. We propose a minimal extension of the SM with a complex singlet scalar $\mathcal{S}$ and a doublet of vector-like quarks. The scalar sector respects CP symmetry, with its CP-odd imaginary component $\chi$ providing a natural dark matter (DM) candidate. The real component of $\mathcal{S}$ serves as the new resonance (750GeV) and explains the diphoton excess of the LHC Run-2. The new scalar degrees of freedom of $\mathcal{S}$ help to stabilize the Higgs vacuum, and can realize the Higgs inflation around GUT scale, consistent with the current cosmology observations. We construct two representative samples A and B of our model for demonstration. We study the mono-jet signals of the DM production from invisible decays Re$(\mathcal{S})\to \chi \chi$ at the LHC Run-2. We further derive the DM relic density bound, and analyze the constraints from direct and indirect DM detections.

   hep-phhep-exPLB(2016)·60 citations
2. 02*

   On the Spiral Structures in Heavy-Ion Collisions

   A. Rustamov🇦🇿 · J. N. Rustamov🇦🇿

   It is well established that many galaxies, like our Milky Way, exhibit spiral patterns. The entire galactic disc rotates about the galactic centre with different speeds; higher closer to the centre, lower at greater distances - that is, galactic discs do not rotate like a solid compact disc. The spiral arms are the part of the galactic disc where many young stars are being born. Since young stars are also brightest, we can see the spiral structure of other galaxies from afar. Typically spiral galaxies are copiously observed at redshifts z ~ 1. The recently observed grand-design galaxy Q2343-BX442 at z=2.18, however, implies uncertain origin of its spiral structure. Indeed such "old" galaxies usually look rather clumpy because of their dynamically hot discs. In this report, based on self-similarity, we argue that spiral structures may also appear in heavy-ion collisions as messengers of phase transitions. Thus, spiral structures in galactic patterns may be traced back to a few microseconds after the Big Bang.

   hep-ph3 citations
3. 03*

   Implications of recent progress in heavy-quark hadroproduction

   M.V. Garzelli🇩🇪 · S. Moch🇩🇪 · G. Sigl🇩🇪

   We discuss recent theoretical progress in heavy-quark hadro-production, in particular focusing on processes involving charm-quarks, and on their implications in different fields of particle phenomenology, from collider to astroparticle physics.

   hep-phPoS(2016)·1 citation
4. 04*

   Rapidity renormalized TMD soft and beam functions at two loops

   Thomas Luebbert🇩🇪 · Joel Oredsson🇩🇪 · Maximilian Stahlhofen🇩🇪

   We compute the transverse momentum dependent (TMD) soft function for the production of a color-neutral final state at the LHC within the rapidity renormalization group (RRG) framework to next-to-next-to-leading order (NNLO). We use this result to extract the universal renormalized TMD beam functions (aka TMDPDFs) in the same scheme and at the same order from known results in another scheme. We derive recurrence relations for the logarithmic structure of the soft and beam functions, which we use to cross check our calculation. We also explicitly confirm the non-Abelian exponentiation of the TMD soft function in the RRG framework at two loops. Our results provide the ingredients for resummed predictions of pT-differential cross sections at NNLL' in the RRG formalism. The RRG provides a systematic framework to resum large (rapidity) logarithms through (R)RG evolution and to assess the associated perturbative uncertainties.

   hep-phJHEP(2016)·98 citations
5. 05*

   Double scattering contribution to small-x processes: Mueller-Navelet jets at the LHC

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

   We study the importance of double parton scattering (DPS) in Mueller-Navelet jets production at the LHC. We evaluate this contribution in kinematics corresponding to existing and possible future measurements at the LHC, for the cross section and the azimuthal correlation of the jets.

   hep-phhep-ex0 citations
6. 06*

   Probing Higgs Width and Top Quark Yukawa Coupling from $t\bar{t}H$ and $t\bar{t}t\bar{t}$ Productions

   Qing-Hong Cao🇨🇳 · Shao-Long Chen🇨🇳 · Yandong Liu🇨🇳

   We demonstrate that four top-quark production is a powerful tool to constrain the top Yukawa coupling. The constraint is robust in the sense that it does not rely on the Higgs boson decay. Taking into account the projection of the $t\bar{t}H$ production by the ATLAS collaobration, we obtain a bound on Higgs boson width, ${\Gamma }_H\le 3.1{\Gamma }_H^{\mathrm{SM}}$, at the 14 TeV LHC with an integrated luminosity of $300{\mathrm{fb}}^{-1}$. Increasing the luminosity to $500{\mathrm{fb}}^{-1}$ yields ${\Gamma }_H\le 2.1{\Gamma }_H^{\mathrm{SM}}$.

   hep-phhep-exPRD(2017)·90 citations
7. 07*

   Reply to "Comment on `Breakdown of the expansion of finite-size corrections to the hydrogen Lamb shift in moments of charge distribution'"

   Franziska Hagelstein🇩🇪 · Vladimir Pascalutsa (KPH, JGU Mainz)🇩🇪

   To comply with the critique of the Comment [J. Arrington, arXiv:1602.01461], we consider another modification of the proton electric form factor, which resolves the "proton-radius puzzle". The proposed modification satisfies all the consistency criteria put forward in the Comment, and yet has a similar impact on the puzzle as that of the original paper. Contrary to the concluding statement of the Comment, it is not difficult to find an ad hoc modification of the form factor at low $Q$ that resolves the discrepancy and is consistent with analyticity constraints. We emphasize once again that we do not consider such an ad hoc modification of the proton form factor to be a solution of the puzzle until a physical mechanism for it is found.

   hep-phnucl-exnucl-thphysics.atom-phPRA(2016)·2 citations
8. 08*

   Next-to-leading power threshold logarithms: a status report

   Domenico Bonocore🇳🇱 · Eric Laenen🇳🇱 · Lorenzo Magnea🇮🇹 · Stacey Melville🇬🇧 · Leonardo Vernazza🇬🇧 · Chris White🇬🇧

   There is ample evidence, dating as far back as Low's theorem, that the universality of soft emissions extends beyond leading power in the soft energy. This universality can, in principle, be exploited to generalise the formalism of threshold resummations beyond leading power in the threshold variable. In the past years, several phenomenological approaches have been partially successful in performing such a resummation. Here, we briefly review some recent developments which pave the way to a solution of this problem, at least for electroweak annihilation processes.

   hep-phPoS(2016)·3 citations
9. 09*

   Photon from the annihilation process with CGC in the $pA$ collision

   Sanjin Benic🇭🇷 · Kenji Fukushima🇯🇵

   We discuss the photon production in the $pA$ collision in a framework of the color glass condensate (CGC) with expansion in terms of the proton color source ${\rho }_p$. We work in a regime where the color density ${\rho }_A$ of the nucleus is large enough to justify the CGC treatment, while soft gluons in the proton could be dominant over quark components but do not yet belong to the CGC regime, so that we can still expand the amplitude in powers of ${\rho }_p$. The zeroth-order contribution to the photon production is known to appear from the Bremsstrahlung process and the first-order corrections consist of the Bremsstrahlung diagrams with pair produced quarks and the annihilation diagrams of quarks involving a gluon sourced by ${\rho }_p$. Because the final states are different there is no interference between these two processes. In this work we elucidate calculation procedures in details focusing on the annihilation diagrams only. Using the McLerran-Venugopalan model for the color average we numerically calculate the photon production rate and discuss functional forms that fit the numerical results.

   hep-phNPA(2017)·28 citations
10. 10*

    Yukawa couplings in 6D gauge-Higgs unification on $T^2/Z_N$ with magnetic fluxes

    Yoshio Matsumoto🇯🇵 · Yutaka Sakamura🇯🇵

    We discuss the Yukawa couplings in 6D gauge-Higgs unification models on $T^2/Z_N$ in the presence of magnetic fluxes. We provide general formulae for them, and numerically evaluate their magnitude in a specific model on $T^2/Z_3$. Thanks to the nontrivial profiles of the zero-mode wave functions, the top quark Yukawa coupling can be reproduced without introducing a large representation of the gauge group for matter fields. However, it is difficult to realize small Yukawa couplings only by the magnetic fluxes and the Wilson-line phases because of the complicated structure of the mode functions on $T^2/Z_N$ ($N=3,4,6$).

    hep-phPTEP(2016)·25 citations
11. 11*

    Symmetries for SM Alignment in multi-Higgs Doublet Models

    Apostolos Pilaftsis🇬🇧

    We derive the complete set of continuous maximal symmetries for Standard Model (SM) alignment that may occur in the tree-level scalar potential of multi-Higgs Doublet Models, with $n>2$ Higgs doublets. Our results generalize the symmetries of SM alignment, without decoupling of large mass scales or fine-tuning, previously obtained in the context of two-Higgs Doublet Models.

    hep-phPRD(2016)·57 citations
12. 12*

    PDFs from nucleons to nuclei

    Alberto Accardi🇺🇸

    I review recent progress in the extraction of unpolarized parton distributions in the proton and in nuclei from a unified point of view that highlights how the interplay between high energy particle physics and lower energy nuclear physics can be of mutual benefit to either field. Areas of overlap range from the search for physics beyond the standard model at the LHC, to the study of the non perturbative structure of nucleons and the emergence of nuclei from quark and gluon degrees of freedom, to the interaction of colored probes in a cold nuclear medium.

    hep-phhep-exnucl-thPoS(2015)·14 citations
13. 13*

    On the uncertainty estimates of the $\sigma$-pole determination by Padé approximants

    Irinel Caprini🇷🇴 · Pere Masjuan🇩🇪 · Jacobo Ruiz de Elvira🇩🇪 · Juan José Sanz-Cillero🇪🇸

    We discuss the determination of the $f_0(500)$ (or $\sigma$) resonance by analytic continuation through Padé approximants of the $\pi \pi$-scattering amplitude from the physical region to the pole in the complex energy plane. The aim is to analyze the uncertainties of the method, having in view the fact that analytic continuation is an ill-posed problem in the sense of Hadamard. Using as input a class of admissible parameterizations of the scalar-isoscalar $\pi \pi$ partial wave, which satisfy with great accuracy the same set of dispersive constraints, we find that the Roy-type integral representations lead to almost identical pole positions for all of them, while the predictions of the Padé approximants have a larger spread, being sensitive to features of the input parameterization that are not controlled by the dispersive constraints. Our conservative conclusion is that the $\sigma$-pole determination by Padé approximants is consistent with the prediction of Roy-type equations, but has an uncertainty almost a factor two larger.

    hep-phhep-exnucl-thPRD(2016)·43 citations
14. 14*

    Higgs vacuum metastability in primordial inflation, preheating, and reheating

    Kazunori Kohri🇯🇵 · Hiroki Matsui🇯🇵

    Current measurements of the Higgs boson mass and top Yukawa coupling suggest that the effective Higgs potential develops an instability below the Planck scale. If the energy scale of inflation is as high as the GUT scale, inflationary quantum fluctuations of the Higgs field can easily destabilize the standard electroweak vacuum and produce a lot of AdS domains. This destabilization during inflation can be avoided if a relatively large nonminimal Higgs-gravity or inflaton-Higgs coupling is introduced. Such couplings generate a large effective mass term for the Higgs, which can raise the effective Higgs potential and suppress the vacuum fluctuation of the Higgs field. After primordial inflation, however, such effective masses drops rapidly and the nonminimal Higgs-gravity or inflaton-Higgs coupling can cause large fluctuations of the Higgs field to be generated via parametric resonance, thus producing AdS domains in the preheating stage. Furthermore, thermal fluctuations of the Higgs field cannot be neglected in the proceeding reheating epoch. We discuss the Higgs vacuum fluctuations during inflation, preheating, and reheating, and show that the Higgs metastability problem is severe unless the energy scale of the inflaton potential is much lower than the GUT scale.

    hep-phastro-ph.COgr-qcPRD(2016)·81 citations
15. 15*

    Large-scale magnetic fields can explain the baryon asymmetry of the Universe

    Tomohiro Fujita🇺🇸 · Kohei Kamada🇺🇸

    Helical hypermagnetic fields in the primordial Universe can produce the observed amount of baryon asymmetry through the chiral anomaly without any ingredients beyond the standard model of particle physics. While they generate no $B-L$ asymmetry, the generated baryon asymmetry survives the spharelon washout effect, because the generating process remains active until the electroweak phase transition. Solving the Boltzmann equation numerically and finding an attractor solution, we show that the baryon asymmetry of our Universe can be explained, if the present large-scale magnetic fields indicated by the blazar observations have a negative helicity and existed in the early Universe before the electroweak phase transition. We also derive the upper bound on the strength of the helical magnetic field, which is tighter than the cosmic microwave background constraint, to avoid the overproduction of baryon asymmetry.

    hep-phastro-ph.COhep-thPRD(2016)·135 citations
16. 16*

    The method of uniqueness and the optical conductivity of graphene: new application of a powerful technique for multi-loop calculations

    S. Teber🇫🇷 · A. V. Kotikov🇷🇺

    We review the method of uniqueness which is a powerful technique for multi-loop calculations in higher dimensional theories with conformal symmetry. We use the method in momentum space and show that it allows a very transparent evaluation of a two-loop massless propagator Feynman diagram with a non-integer index on the central line. The result is applied to the computation of the optical conductivity of graphene at the infra-red Lorentz invariant fixed point. The effect of counter-terms is analysed. A brief comparison with the non-relativistic case is included.

    ↳ hep-thcond-mat.mes-hallhep-phTheor.Math.Phys.(2017)·28 citations
17. 17*

    The quest for an electric dipole moment of the neutron

    P. Schmidt-Wellenburg🇨🇭

    Until this day no electric dipole moment of the neutron (nEDM) has been observed. Why it is so vanishing small, escaping detection in the last 50 years, is not easy to explain. In general it is considered as the most sensitive probe for the violation of the combined symmetry of charge and parity (CP). A discovery could shed light on the poorly understood matter/anti-matter asymmetry of the universe. As nucleon it might one day help to distinguish different sources of CP-violation in combination with measurements of the electron and diamagnetic EDMs. This proceedings articles presents an overview of the most important concepts in searches for an nEDM and presents a brief overview of the world wide efforts.

    ↳ nucl-exhep-exhep-phphysics.ins-detAIP Conf.Proc.(2016)·20 citations
18. 18*

    Coincidence of a high-fluence blazar outburst with a PeV-energy neutrino event

    M. Kadler🇩🇪 · F. Krauß🇩🇪 · K. Mannheim🇩🇪 · R. Ojha🇺🇸 · C. Müller🇩🇪 · R. Schulz🇩🇪 · G. Anton🇩🇪 · W. Baumgartner🇺🇸 · T. Beuchert🇩🇪 · S. Buson🇮🇹 · B. Carpenter🇺🇸 · T. Eberl🇩🇪 and 32 other authors

    The discovery of extraterrestrial very-high-energy neutrinos by the IceCube collaboration has launched a quest for the identification of their astrophysical sources. Gamma-ray blazars have been predicted to yield a cumulative neutrino signal exceeding the atmospheric background above energies of 100 TeV, assuming that both the neutrinos and the gamma-ray photons are produced by accelerated protons in relativistic jets. Since the background spectrum falls steeply with increasing energy, the individual events with the clearest signature of being of an extraterrestrial origin are those at PeV energies. Inside the large positional-uncertainty fields of the first two PeV neutrinos detected by IceCube, the integrated emission of the blazar population has a sufficiently high electromagnetic flux to explain the detected IceCube events, but fluences of individual objects are too low to make an unambiguous source association. Here, we report that a major outburst of the blazar PKS B1424-418 occurred in temporal and positional coincidence with the third PeV-energy neutrino event (IC35) detected by IceCube. Based on an analysis of the full sample of gamma-ray blazars in the IC35 field and assuming a photo-hadronic emission model, we show that the long-term average gamma-ray emission of blazars as a class is in agreement with both the measured all-sky flux of PeV neutrinos and the spectral slope of the IceCube signal. The outburst of PKS B1424-418 has provided an energy output high enough to explain the observed PeV event, indicative of a direct physical association.

    ↳ astro-ph.HEhep-phNat.Phys.(2016)·251 citations
19. 19*

    High order flow harmonics of identified hadrons in 2.76 A TeV Pb+Pb collisions

    Hao-jie Xu🇨🇳 · Zhuopeng Li🇨🇳 · Huichao Song🇨🇳

    Using iEBE-VISHNU hybrid model with the AMPT initial conditions, we study the higher order flow harmonics of identified hadrons in 2.76 A TeV Pb+Pb collisions. Comparison with the recent ALICE measurements at 20-30\% centrality shows that our calculations nicely describe the data below 2 GeV, especially for the $v_2$, $v_3$ and $v_4$ mass-orderings among pions, kaons and protons. We also extended the calculations to other centrality bins, which presents similar mass-ordering patterns for these flow harmonics as the ones observed at 20-30\% centrality. In the later part of this article, we explore the development of $v_n$ mass ordering/splitting during the hadronic evolution through the comparison runs from iEBE-VISHNU hybrid model and pure hydrodynamics with different decoupling temperatures.

    ↳ nucl-thhep-phnucl-exPRC(2016)·60 citations
20. 20*

    Tachyonic approach to neutrino dark matter

    Eduard G. Mychelkin🇰🇿 · Maxim A. Makukov🇰🇿

    We apply a new approach based on three relativistic groups (bradyon, tachyon and instanton) forming the `Lorentz groupoid' which allows, in particular, to consider tachyons without introducing imaginary masses and negative energies (related, as known, to violation of causality and unitarity). This leads to effectively scalar conglomerate composed of tachyonic neutrino and antineutrino spinor wave functions as a viable model for stationary dark matter. We also briefly discuss a relevant early non-stationary high-energy stage of the universe evolution.

    ↳ physics.gen-phastro-ph.COgr-qchep-ph0 citations
21. 21*

    First evidence of running cosmic vacuum: challenging the concordance model

    Joan Sola🇪🇸 · Adria Gomez-Valent🇪🇸 · Javier de Cruz Perez🇪🇸

    Despite the fact that a rigid $\Lambda$-term is a fundamental building block of the concordance $\Lambda$CDM model, we show that a large class of cosmological scenarios with dynamical vacuum energy density ${\rho }_{\Lambda }$ and/or gravitational coupling $G$, together with a possible non-conservation of matter, are capable of seriously challenging the traditional phenomenological success of the $\Lambda$CDM. In this paper, we discuss these "running vacuum models" (RVM's), in which ${\rho }_{\Lambda }={\rho }_{\Lambda }(H)$ consists of a nonvanishing constant term and a series of powers of the Hubble rate. Such generic structure is potentially linked to the quantum field theoretical description of the expanding Universe. By performing an overall fit to the cosmological observables $SNIa+BAO+H(z)+LSS+BBN+CMB$ (in which the WMAP9, Planck 2013 and Planck 2015 data are taken into account), we find that the class of RVM's appears significantly more favored than the $\Lambda$CDM, namely at an unprecedented level of $\gtrsim 4.2\sigma$. Furthermore, the Akaike and Bayesian information criteria confirm that the dynamical RVM's are strongly preferred as compared to the conventional rigid $\Lambda$-picture of the cosmic evolution.

    ↳ astro-ph.COgr-qchep-phhep-thApJ(2017)·251 citations
22. 22*

    All orders results for self-crossing Wilson loops mimicking double parton scattering

    Lance J. Dixon🇺🇸 · Ilya Esterlis🇺🇸

    Loop-level scattering amplitudes for massless particles have singularities in regions where tree amplitudes are perfectly smooth. For example, a $2\to 4$ gluon scattering process has a singularity in which each incoming gluon splits into a pair of gluons, followed by a pair of $2\to 2$ collisions between the gluon pairs. This singularity mimics double parton scattering because it occurs when the transverse momentum of a pair of outgoing gluons vanishes. The singularity is logarithmic at fixed order in perturbation theory. We exploit the duality between scattering amplitudes and polygonal Wilson loops to study six-point amplitudes in this limit to high loop order in planar $\mathcal{N}=4$ super-Yang-Mills theory. The singular configuration corresponds to the limit in which a hexagonal Wilson loop develops a self-crossing. The singular terms are governed by an evolution equation, in which the hexagon mixes into a pair of boxes; the mixing back is suppressed in the planar (large $N_c$) limit. Because the kinematic dependence of the box Wilson loops is dictated by (dual) conformal invariance, the complete kinematic dependence of the singular terms for the self-crossing hexagon on the one nonsingular variable is determined to all loop orders. The complete logarithmic dependence on the singular variable can be obtained through nine loops, up to a couple of constants, using a correspondence with the multi-Regge limit. As a byproduct, we obtain a simple formula for the leading logs to all loop orders. We also show that, although the MHV six-gluon amplitude is singular, remarkably, the transcendental functions entering the non-MHV amplitude are finite in the same limit, at least through four loops.

    ↳ hep-thhep-phJHEP(2016)·29 citations
23. 23*

    Transport Coefficient to Trace Anomaly in the Clustering of Color Sources Approach

    J. Dias de Deus🇵🇹 · A. S. Hirsch🇺🇸 · C. Pajares🇪🇸 · R. P. Scharenberg🇺🇸 · B. K. Srivastava🇺🇸

    From our previously obtained shear viscosity to entropy density ratio ($\eta /s$) in the framework of clustering of color sources (Color String Percolation Model: CSPM), we calculate the jet quenching parameter $\hat{q}$ and trace anomaly $\Delta =(\epsilon -3p)/T^4$ as a function of temperature. It is shown that the scaled $\hat{q}/T^3$ is in agreement with the recent JET Collaboration estimates. The inverse of $\eta /s$ is found to represent $\Delta$. The results for $\Delta$ are in excellent agreement with Lattice Quantum Chromo Dynamics (LQCD) simulations. From the trace anomaly and energy density $ϵ$, the equation of state is obtained as a function of temperature and compared with LQCD simulations. It is possible that there is a direct connection between the $\eta /s$ and $\Delta$. Thus the estimate of transport coefficient $\eta /s$ provides $\hat{q}$ and $\Delta$ as a function of temperature. Both $\Delta$ and $\eta /s$ describe the transition from a strongly coupled QGP to a weakly coupled QGP.

    ↳ nucl-thhep-lathep-phnucl-exPRC(2016)·16 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.