Thu·Dec 24, 2015Thursday·December 24, 2015

1. 01*

   Initial state azimuthal anisotropies in small collision systems

   T. Lappi🇫🇮

   Strong multiparticle azimuthal correlations have recently been observed in high energy proton-nucleus collisions. While final state collective effects can be responsible for many of the observations, the domain structure in the classical color field of a high energy nucleus also naturally leads to such correlations. We describe recent calculations of the momentum space 2-particle cumulant azimuthal anisotropy coefficients v_n{2}, n=2,3,4 from fundamental representation Wilson line distributions describing the high energy nucleus. We find significant differences between Wilson lines from the MV model and from JIMWLK evolution. We also discuss the relation of this calculation to earlier work on the ridge correlation obtained in the "glasma graph" approximation, and to the "color electric field domain model."

   hep-phnucl-thNPA(2016)·3 citations
2. 02*

   750 GeV Resonance in the Dark Left-Right Model

   Ujjal Kumar Dey🇮🇳 · Subhendra Mohanty🇮🇳 · Gaurav Tomar🇮🇳

   We explain the $750$ GeV diphoton resonance in the context of the dark left-right symmetric model. A global symmetry in this model, stabilizes the dark matter and ensures that the scalar couples dominantly to gluons and photons. The branching fraction of the scalar to diphoton is large as a consequence of the symmetries of the theory. The benchmark values assumed to fit the diphoton signal also give the correct relic density of dark matter and muon $(g-2)$. A specific prediction of this model is that the dark matter has a mass of 200 GeV.

   hep-phPLB(2016)·118 citations
3. 03*

   Trinification can explain the di-photon and di-boson LHC anomalies

   Giulio Maria Pelaggi🇮🇹 · Alessandro Strumia🇨🇭 · Elena Vigiani🇮🇹

   LHC data show a diphoton excess at 750 GeV and a less significant diboson excess around 1.9 TeV. We propose trinification as a common source of both anomalies. The 1.9 TeV excess can be produced by the lightest extra vector: a $W_R^{\pm }$ with a gauge coupling $g_R\approx 0.44$ that does not decay into leptons. Furthermore, trinification predicts extra scalars. One of them can reproduce the $\gamma \gamma$ excess while satisfying constraints from all other channels, given the specific set of extra fermions predicted by trinification.

   hep-phJHEP(2016)·109 citations
4. 04*

   New vector bosons and the diphoton excess

   Jorge de Blas🇮🇹 · Jose Santiago🇪🇸 · Roberto Vega-Morales🇪🇸

   We consider the possibility that the recently observed diphoton excess at $\sim 750$ GeV can be explained by the decay of a scalar particle ($\phi$) to photons. If the scalar is the remnant of a symmetry-breaking sector of some new gauge symmetry, its coupling to photons can be generated by loops of the charged massive vectors of the broken symmetry. If these new $W^{\prime }$ vector bosons carry color, they can also generate an effective coupling to gluons. In this case the diphoton excess could be entirely explained in a simplified model containing just $\phi$ and $W^{\prime }$. On the other hand if $W^{\prime }$ does not carry color, we show that, provided additional colored particles exist to generate the required $\phi$ to gluon coupling, the diphoton excess could be explained by the same $W^{\prime }$ commonly invoked to explain the diboson excess at $\sim 2$ TeV. We also explore possible connections between the diphoton and diboson excesses with the anomalous $t\bar{t}$ forward-backward asymmetry.

   hep-phhep-exPLB(2016)·124 citations
5. 05*

   Interference contributions to gluon initiated heavy Higgs production in the Two-Higgs-Doublet Model

   Nicolas Greiner🇨🇭 · Stefan Liebler🇩🇪 · Georg Weiglein🇩🇪

   We discuss the production of a heavy neutral Higgs boson of a CP-conserving Two-Higgs-Doublet Model in gluon fusion and its decay into a four-fermion final state, $gg(\to VV)\to e^{+}{e}^{-}{\mu }^{+}{\mu }^{-}/e^{+}{e}^{-}{\nu }_l{\bar{\nu }}_l$. We investigate the interference contributions to invariant mass distributions of the four-fermion final state and other relevant kinematical observables. The relative importance of the different contributions is quantified for the process in the on-shell approximation, $gg\to ZZ$. We show that interferences of the heavy Higgs with the light Higgs boson and background contributions are essential for a correct description of the differential cross section. Even though they contribute below $\mathcal{O}(10\%)$ to those heavy Higgs signal cross sections, to which the experiments at the Large Hadron Collider were sensitive in its first run, we find that they are sizeable in certain regions of the parameter space that are relevant for future heavy Higgs boson searches. In fact, the interference contributions can significantly enhance the experimental sensitivity to the heavy Higgs boson.

   hep-phEPJC(2016)·15 citations
6. 06*

   Operator Constraints for Twist-3 Functions and Lorentz Invariance Properties of Twist-3 Observables

   Koichi Kanazawa🇺🇸 · Yuji Koike🇯🇵 · Andreas Metz🇺🇸 · Daniel Pitonyak🇺🇸 · Marc Schlegel🇩🇪

   We investigate the behavior under Lorentz tranformations of perturbative coefficient functions in a collinear twist-3 formalism relevant for high-energy observables including transverse polarization of hadrons. We argue that those perturbative coefficient functions can, {\it a priori}, acquire quite different yet Lorentz-invariant forms in various frames. This somewhat surprising difference can be traced back to a general dependence of the perturbative coefficient functions on lightcone vectors which are introduced by the twist-3 factorization formulae and which are frame-dependent. One can remove this spurious frame dependence by invoking so-called Lorentz invariance relations (LIRs) between twist-3 parton correlation functions. Some of those relations for twist-3 distribution functions were discussed in the literature before. In this paper we derive the corresponding LIRs for twist-3 fragmentation functions. We explicitly demonstrate that these LIRs remove the lightcone vector dependence by considering transverse spin observables in the single-inclusive production of hadrons in lepton-nucleon collisions, $\ell N\to hX$. With the LIRs in hand, we also show that twist-3 observables in general can be written solely in terms of three-parton correlation functions.

   hep-phPRD(2016)·102 citations
7. 07*

   Singlets in Composite Higgs Models in light of the LHC di-photon searches

   Alexander Belyaev🇬🇧 · Giacomo Cacciapaglia🇫🇷 · Haiying Cai🇫🇷 · Thomas Flacke🇰🇷 · Alberto Parolini🇰🇷 · Hugo Serôdio🇰🇷

   Models of compositeness can successfully address the origin of the Higgs boson, as a pseudo Nambu Goldstone boson (pNGB) of a spontaneously broken global symmetry, and flavour physics via the partial compositeness mechanism. If the dynamics is generated by a confining gauge group with fermionic matter content, there exists only a finite set of models that have the correct properties to account for the Higgs and top partners at the same time. In this letter we explore the theory space of this class of models: remarkably, all of them contain - beyond the pNGB Higgs - a pNGB singlet, $a$, which couples to Standard Model gauge bosons via Wess-Zumino-Witten interactions, thus providing naturally a resonance in di-boson at the LHC. With the assumption that the recently reported di-photon excess at 750 GeV at the LHC arises from the a-resonance, we propose a generic approach on how to delineate the best candidate for composite Higgs models with top-partners. We find that constraints from other di-boson searches severely reduce the theory space of the models under consideration. For the models which can explain the di-photon excess, we make precise and testable predictions for the width and other di-boson resonance searches.

   hep-phPRD(2016)·140 citations
8. 08*

   Asymmetric Dark Matter in the Sun and the Diphoton Excess at the LHC

   P.S. Bhupal Dev🇩🇪 · Daniele Teresi🇧🇪

   It has been recently pointed out that a momentum-dependent coupling of the asymmetric Dark Matter (ADM) with nucleons can explain the broad disagreement between helioseismological observables and the predictions of standard solar models. In this paper, we propose a minimal simplified ADM model consisting of a scalar and a pseudoscalar mediator, in addition to a Dirac fermionic DM, for generating such momentum-dependent interactions. Remarkably, the pseudoscalar with mass around 750 GeV can simultaneously explain the solar anomaly and the recent diphoton excess observed by both ATLAS and CMS experiments in the early $\sqrt{s}=13$ TeV LHC data. In this framework, the total width of the resonance is naturally large, as suggested by the ATLAS experiment, since the resonance mostly decays to the ADM pair. The model predicts the existence of a new light scalar in the GeV range, interacting with quarks, and observable dijet, monojet and $t\bar{t}$ signatures for the 750 GeV resonance at the LHC.

   hep-phastro-ph.COastro-ph.SRhep-exPRD(2016)·133 citations
9. 09*

   Parton Distribution in Pseudoscalar Mesons with a Light-Front Constituent Quark Model

   J. P. B. C. de Melo (Laboratorio de Fisica Teorica e Computacional, Universidade Cruzeiro do Sul)🇧🇷 · Isthiaq Ahmed (Laboratorio de Fisica Teorica e Computacional, Universidade Cruzeiro do Sul and National Center for Physics, Quaidi-i-Azam University Campus)🇧🇷 · Kazuo Tsushima (Laboratorio de Fisica Teorica e Computacional, Universidade Cruzeiro do Sul)🇧🇷

   We compute the distribution amplitudes of the pion and kaon in the light-front constituent quark model with the symmetric quark-bound state vertex function. In the calculation we explicitly include the flavor-SU(3) symmetry breaking effect in terms of the constituent quark masses of the up (down) and strange quarks. To calculate the kaon parton distribution functions~(PDFs), we use both the conditions in the light-cone wave function, i.e., when $\bar{s}$ quark is on-shell, and when $u$ quark is on-shell, and make a comparison between them. The kaon PDFs calculated in the two different conditions clearly show asymmetric behaviour due to the flavor SU(3)-symmetry breaking implemented by the quark masses.

   hep-phAIP Conf.Proc.(2016)·19 citations
10. 10*

    Gauged Two Higgs Doublet Model confronts the LHC 750 GeV di-photon anomaly

    Wei-Chih Huang🇩🇪 · Yue-Lin Sming Tsai🇯🇵 · Tzu-Chiang Yuan🇹🇼

    In light of the recent 750 GeV diphoton anomaly observed at the LHC, we study the possibility of accommodating the deviation from the standard model prediction based on the recently proposed Gauged Two Higgs Doublet Model. The model embeds two Higgs doublets into a doublet of a non-abelian gauge group $SU(2{)}_H$, while the standard model $SU(2{)}_L$ right-handed fermion singlets are paired up with new heavy fermions to form $SU(2{)}_H$ doublets, and $SU(2{)}_L$ left-handed fermion doublets are singlets under $SU(2{)}_H$. An $SU(2{)}_H$ scalar doublet, which provides masses to the new heavy fermions as well as the $SU(2{)}_H$ gauge bosons, can be produced via gluon fusion and subsequently decays into two photons with the new fermions circulating the triangle loops to account for the deviation from the standard model prediction.

    hep-phNPB(2016)·119 citations
11. 11*

    Naturalness in Type II seesaw model and implications for physical scalars

    Mohamed Chabab🇲🇦 · Michel Capdequi-Peyranère🇫🇷 · Larbi Rahili🇲🇦

    In this paper we consider a minimal extension to the standard model by a scalar triplet field with hypercharge $Y=2$. This model relies on the seesaw mechanism which provides a consistent explication of neutrino mass generation. We show from naturalness considerations that the Veltman condition is modified by virtue of the additional scalar charged states and that quadratic divergencies at one loop can be driven to zero within the allowed space parameter of the model, the latter is severely constrained by unitarity, boundedness from below and is consistent with the di-photon Higgs decay data of LHC. Furthermore, we analyse the naturalness condition effects to the masses of heavy Higgs bosons $H^0$, $A^0$, $H^{\pm }$ and $H^{\pm \pm }$, providing a drastic reduction of the ranges of variation of $m_{H^{\pm }}$ and $m_{H^{\pm \pm }}$ with an upper bounds at $288$ and $351$~GeV respectively, while predicting an almost degeneracy for the other neutral Higgs bosons $H^0$, $A^0$ at about $207$~GeV.

    hep-phPRD(2016)·35 citations
12. 12*

    Mesons in strong magnetic fields: (I) General analyses

    Koichi Hattori🇯🇵 · Toru Kojo🇺🇸 · Nan Su🇩🇪

    We study properties of neutral and charged mesons in strong magnetic fields |eB|>> Lambda_QCD^2 with Lambda_QCD being the QCD renormalization scale. Assuming long-range interactions, we examine magnetic-field dependences of various quantities such as the constituent quark mass, chiral condensate, meson spectra, and meson wavefunctions by analyzing the Schwinger-Dyson and Bethe-Salpeter equations. Based on the density of states obtained from these analyses, we extend the hadron resonance gas (HRG) model to investigate thermodynamics at large B. As B increases the meson energy behaves as a slowly growing function of the meson's transverse momenta, and thus a large number of meson states is accommodated in the low energy domain; the density of states at low temperature is proportional to B^2. This extended transverse phase space in the infrared regime significantly enhances the HRG pressure at finite temperature, so that the system reaches the percolation or chiral restoration regime at lower temperature compared to the case without a magnetic field; this simple picture would offer a gauge invariant and intuitive explanation of the inverse magnetic catalysis.

    hep-phhep-lathep-thnucl-thNPA(2016)·75 citations
13. 13*

    Modification of generalized vector form factors and transverse charge densities of the nucleon in nuclear matter

    Ju-Hyun Jung🇦🇹 · Ulugbek Yakhshiev🇰🇷 · Hyun-Chul Kim🇰🇷

    We investigate the medium modification of the generalized vector form factors of the nucleon, which include the electromagnetic and energy-momentum tensor form factors, based on an in-medium modified $\pi$-$\rho$-$\omega$ soliton model. We find that the vector form factors of the nucleon in nuclear matter fall off faster than those in free space, which implies that the charge radii of the nucleon become larger in nuclear medium than in free space. We also compute the corresponding transverse charge densities of the nucleon in nuclear matter, which clearly reveal the increasing of the nucleon size in nuclear medium.

    hep-phhep-latnucl-thPRD(2016)·10 citations
14. 14*

    Unravelling the non-standard top and Higgs couplings in associated top-Higgs production at the High-luminosity LHC

    Saurabh D. Rindani🇮🇳 · Pankaj Sharma🇦🇺 · Ambresh Shivaji🇮🇹

    We study the sensitivities of non-standard top and Higgs couplings in the $pp\to thj$ process at the 14 TeV high-luminosity run of Large Hadron Collider (HL-LHC). We calculate top polarization and construct various lab-frame observables to study their sensitivities on anomalous couplings at HL-LHC. Both anomalous Wtb and hVV couplings contribute in the production process. However, only the former contributes in top decay and only the latter takes part in Higgs decay. We study this interesting interplay of couplings in the production and decay observables. In production, these couplings significantly affect the top polarization. As a measure of top polarization, we look at decay-lepton angular distributions in the laboratory frame and study the effect of anomalous couplings on these distributions. We construct certain asymmetries to study the sensitivity of these distributions to top quark couplings. In particular, real and imaginary parts of an hVV coupling and real part of a Wtb coupling f2R significantly alter the top polarization and, in turn, affect the decay-lepton distributions in laboratory frame.

    hep-phPoS(2016)·1 citation
15. 15*

    The impact of the medium and the jet-medium coupling on jet measurements at RHIC and LHC

    Barbara Betz🇩🇪 · Florian Senzel🇩🇪 · Carsten Greiner🇩🇪 · Miklos Gyulassy🇺🇸

    We compare a perturbative QCD-based jet-energy loss model to the measured data of the pion nuclear modification factor and the high-pT elliptic flow at RHIC and LHC energies. This jet-energy loss model (BBMG) is currently coupled to state-of-the-art hydrodynamic descriptions. We report on a model extension to medium backgrounds generated by the parton cascade BAMPS. In addition, we study the impact of realistic medium transverse flow fields and a jet-medium coupling which includes the effects of the jet energy, the temperature of the bulk medium, and non-equilibrium effects close to the phase transition. By contrasting the two different background models, we point out that the description of the high-pT elliptic flow for a non-fluctuating medium requires to include such a jet-medium coupling and the transverse flow fields. While the results for both medium backgrounds show a remarkable similarity, there is an impact of the background medium and the background flow on the high-pT elliptic flow.

    hep-phhep-exnucl-th3 citations
16. 16*

    The 750 GeV diphoton excess and its explanation in 2-Higgs Doublet Models with a real inert scalar multiplet

    Stefano Moretti🇬🇧 · Kei Yagyu🇬🇧

    We discuss a possible explanation of the recently observed diphoton excess at around 750 GeV as seen by the ATLAS and CMS experiments at the Large Hadron Collider. We calculate the cross section of the diphoton signature in 2-Higgs Doublet Models with the addition of a real isospin scalar multiplet without a vacuum expectation value, where a neutral component of such a representation can be a dark matter candidate. We find that the branching fraction of an additional CP-even Higgs boson $H$ from the doublet fields into the diphoton mode can be significantly enhanced, by up to a factor of $10^3$, with respect to the case of the simple 2-Higgs Doublet Model. Such a sizable enhancement is realized due to multi-charged inert particle loops entering the $H\to \gamma \gamma$ decay mode. Through this enhancement, we obtain a suitable cross section of the $gg\to H\to \gamma \gamma$ process to explain the data with the fixed mass of $H$ being 750 GeV.

    hep-phPRD(2016)·94 citations
17. 17*

    Interpreting 750 GeV diphoton excess in SU(5) grand unified theory

    Ketan M. Patel🇮🇳 · Pankaj Sharma🇦🇺

    The ATLAS and CMS experiments at the LHC have found significant excess in the diphoton invariant mass distribution near 750 GeV. We interpret this excess in a predictive nonsupersymmetric SU(5) grand unified framework with a singlet scalar and light adjoint fermions. The 750 GeV resonance is identified as a gauge singlet scalar. Both its production and decays are induced by 24 dimensional adjoint fermions predicted within SU(5). The adjoint fermions are assumed to be odd under $Z_2$ symmetry which forbids their direct coupling to the standard model fermions. We show that the observed diphoton excess can be explained with sub-TeV adjoint fermions and with perturbative Yukawa coupling. A narrow width scenario is more preferred while a simultaneous explanation of observed cross section and large total decay width requires some of the adjoint fermions lighter than 375 GeV. The model also provides a singlet fermion as a candidate of cold dark matter. The gauge coupling unification is achieved in the framework by introducing color sextet scalars while being consistent with the proton decay constraint.

    hep-phPLB(2016)·99 citations
18. 18*

    Double vector meson production in $\gamma \gamma$ interactions at hadronic colliders

    V. P. Goncalves🇧🇷 · B. D. Moreira🇧🇷 · F. S. Navarra🇧🇷

    In this paper we revisit the double vector meson production in $\gamma \gamma$ interactions at heavy ion collisions and present, by the first time, predictions for the $\rho \rho$ and $J/\Psi J/\Psi$ production in proton -- nucleus and proton -- proton collisions. In order to obtain realistic predictions for rapidity distributions and total cross sections for the double vector production in ultra peripheral hadronic collisions we take into account of the description of $\gamma \gamma \to VV$ cross section at low energies as well as its behaviour at large energies, associated to the gluonic interaction between the color dipoles. Our results demonstrate that the double $\rho$ production is dominated by the low energy behaviour of the $\gamma \gamma \to VV$ cross section. In contrast, for the double $J/\Psi$ production, the contribution associated to the description of the QCD dynamics at high energies contributes significantly, mainly in $pp$ collisions. Predictions for the RHIC, LHC, FCC and CEPC - SPPC energies are shown.

    hep-phhep-exnucl-exnucl-thEPJC(2016)·24 citations
19. 19*

    Interpreting the 750 GeV diphoton excess in minimal extensions of Two-Higgs-Doublet models

    Marcin Badziak🇵🇱

    It is shown that the 750 GeV diphoton excess can be explained in extensions of Two-Higgs-Doublet Models that do not involve large multiplicities of new electromagnetically charged states. The key observation is that at moderate and large $\tan \beta$ the total decay width of the 750 GeV Higgs is strongly reduced as compared to the Standard Model. This allows for much more economical choices of new states that enhance the diphoton signal to fit the data. In particular, it is shown that one family of vector-like quarks and leptons with SM charges is enough to explain the 750 GeV diphoton excess. Moreover, such charge assignment can keep the 125 GeV Higgs signal rates exactly at the SM values. The scenario can interpret the diphoton excess provided that the total decay width of a hypothetical resonance that would be measured at the LHC turns out to not exceed few GeV.

    hep-phPLB(2016)·111 citations
20. 20*

    Determination of the carrier envelope phase for short, circularly polarized laser pulses

    Alexander I. Titov🇷🇺 · Burkhard Kampfer🇩🇪 · Atsushi Hosaka🇯🇵 · Tobias Nousch🇩🇪 · Daniel Seipt🇩🇪

    We analyze the impact of the carrier envelope phase on the differential cross sections of the Breit-Wheeler and the generalized Compton scattering in the interaction of a charged electron (positron) with an intensive ultra-short electromagnetic (laser) pulse. The differential cross sections as a function of the azimuthal angle of the outgoing electron have a clear bump structure, where the bump position coincides with the value of the carrier phase. This effect can be used for the carrier envelope phase determination.

    hep-phPRD(2016)·27 citations
21. 21*

    The ${\eta }^{\prime }$ transition form factor from space- and time-like experimental data

    Rafel Escribano🇪🇸 · Sergi Gonzalez-Solis🇪🇸 · Pere Masjuan🇩🇪 · Pablo Sanchez-Puertas🇩🇪

    The ${\eta }^{\prime }$ transition form factor is reanalyzed in view of the recent BESIII first observation of the Dalitz decay ${\eta }^{\prime }\to \gamma e^{+}{e}^{-}$ in both space- and time-like regions at low and intermediate energies using the Padé approximants method. The present analysis provides a suitable parameterization for reproducing the measured form factor in the whole energy region and allows to extract the corresponding low-energy parameters together with a prediction of its values at the origin, related to ${\Gamma }_{{\eta }^{\prime }\to \gamma \gamma }$, and the asymptotic limit. The $\eta$-${\eta }^{\prime }$ mixing is reassessed within a mixing scheme compatible with the large-$N_c$ chiral perturbation theory at next-to-leading order, with particular attention to the OZI-rule--violating parameters. The $J/\psi$, $Z\to {\eta }^{(\prime )}\gamma$ decays are also considered and predictions reported.

    hep-phhep-exnucl-thPRD(2016)·105 citations
22. 22*

    Diphoton resonance at 750 GeV in the broken MRSSM

    Sabyasachi Chakraborty🇮🇳 · Amit Chakraborty🇮🇳 · Sreerup Raychaudhuri🇮🇳

    Non-observation of superpartners of the Standard Model particles at the early runs of the LHC provide strong motivation for an $R$-symmetric minimal supersymmetric Standard Model, or MRSSM. This model also comes with a pair of extra scalars which couple only to superpartners at the tree level. We demonstrate that in the limit when the $U(1{)}_R$ symmetry is broken, one of these scalars develops all the properties necessary to explain the 750 GeV diphoton resonance recently observed at the LHC, as well as the non-observation of associated signals in other channels. Some confirmatory tests in the upcoming LHC runs are proposed.

    hep-phPRD(2016)·109 citations
23. 23*

    Structure of $X_b$ from line shape analysis

    Yue Ma🇯🇵 · Guo-Ying Chen🇨🇳

    We study the production line shape of $B^{\ast }\bar{B}$ near threshold, where the $B^{\ast }\bar{B}$ pair comes from the resonance $X_b$. Our study shows that the line shape depends sensitively on the binding energy and the probability of finding an elementary state in the physical bound state. Both of the two parameters are crucial to identify the structure of $X_b$. Therefore, the line shape measurement can shed light on the structure of $X_b$.

    hep-phhep-exMod.Phys.Lett.A(2016)·0 citations
24. 24*

    Littlest Seesaw

    Stephen F. King🇬🇧

    We propose the Littlest Seesaw (LS) model consisting of just two right-handed neutrinos, where one of them, dominantly responsible for the atmospheric neutrino mass, has couplings to $({\nu }_e,{\nu }_{\mu },{\nu }_{\tau })$ proportional to $(0,1,1)$, while the subdominant right-handed neutrino, mainly responsible for the solar neutrino mass, has couplings to $({\nu }_e,{\nu }_{\mu },{\nu }_{\tau })$ proportional to $(1,n,n-2)$. This constrained sequential dominance (CSD) model preserves the first column of the tri-bimaximal (TB) mixing matrix (TM1) and has a reactor angle ${\theta }_{13}\sim (n-1)\frac{\sqrt{2}}{3}\frac{m_2}{m_3}$. This is a generalisation of CSD ($n=1$) which led to TB mixing and arises almost as easily if $n\ge 1$ is a real number. We derive exact analytic formulas for the neutrino masses, lepton mixing angles and CP phases in terms of the four input parameters and discuss exact sum rules. We show how CSD ($n=3$) may arise from vacuum alignment due to residual symmetries of $S_4$. We propose a benchmark model based on $S_4\times Z_3\times Z_3^{\prime }$, which fixes $n=3$ and the leptogenesis phase $\eta =2\pi /3$, leaving only two inputs $m_a$ and $m_b=m_{ee}$ describing $\Delta m_{31}^2$, $\Delta m_{21}^2$ and $U_{PMNS}$. The LS model predicts a normal mass hierarchy with a massless neutrino $m_1=0$ and TM1 atmospheric sum rules. The benchmark LS model additionally predicts: solar angle ${\theta }_{12}=34^{\circ }$, reactor angle ${\theta }_{13}=8.7^{\circ }$, atmospheric angle ${\theta }_{23}=46^{\circ }$, and Dirac phase ${\delta }_{CP}=-87^{\circ }$.

    hep-phJHEP(2016)·72 citations
25. 25*

    Heavy-flavour transport: from large to small systems

    A. Beraudo🇮🇹 · A. De Pace🇮🇹 · M. Monteno🇮🇹 · M. Nardi🇮🇹 · F. Prino🇮🇹

    Predictions for heavy-flavour production in relativistic heavy-ion experiments provided by the POWLANG transport setup, including now also an in-medium hadronization model, are displayed, After showing some representative findings for the Au-Au and Pb-Pb cases, a special focus will be devoted to the results obtained in the small systems formed in proton(deuteron)-nucleus collisions, where recent experimental data suggest the possible formation of a medium featuring a collective behaviour.

    hep-phnucl-exnucl-thNPA(2016)·1 citation
26. 26*

    Strong CP Problem, Neutrino Masses and the 750 GeV Diphoton Resonance

    Qing-Hong Cao🇨🇳 · Shao-Long Chen🇨🇳 · Pei-Hong Gu🇨🇳

    We present an $SU(3{)}_c^{}\times SU(2{)}_L^{}\times SU(2{)}_R^{}\times U(1{)}_L^{}\times U(1{)}_R^{}\to SU(3{)}_c^{}\times SU(2{)}_L^{}\times SU(2{)}_R^{}\times U(1{)}_{B-L}^{}$ left-right symmetric model with a discrete parity symmetry to realize a universal seesaw scenario. The model can simultaneously solve the strong CP problem without resorting to the unobserved axion and explain the 750 GeV diphoton resonance reported recently by the ATLAS and CMS collaborations at the LHC. Owing to large suppressions in the two-loop induced Dirac mass terms, the Majorana mass matrices of left- and right-handed neutrinos naturally share the same structure. That allows us to quantitatively study the neutrinoless double beta decay induced by the right-handed currents.

    hep-phhep-ex96 citations
27. 27*

    Jet formation and interference in a thin QCD medium

    Jorge Casalderrey-Solana🇬🇧 · Daniel Pablos🇪🇸 · Konrad Tywoniuk🇪🇸

    In heavy-ion collisions, an abundant production of high-energy QCD jets allows to study how these multiparticle sprays are modified as they pass through the quark-gluon plasma. In order to shed new light on this process, we compute the inclusive two-gluon rate off a hard quark propagating through a color deconfined medium at first order in medium opacity. We explicitly impose an energy ordering of the two emitted gluons, such that the "hard" gluon can be thought of as belonging to the jet substructure while the other is a "soft" emission (which can be collinear or medium-induced). Our analysis focusses on two specific limits that clarify the modification of the additional angle- and formation time-ordering of splittings. In one limit, the formation time of the "hard" gluon is short compared to the "soft" gluon formation time, leading to a probabilistic formula for production of and subsequent radiation off a quark-gluon antenna. In the other limit, the ordering of formation is reverted, which automatically leads to the fact that the jet substructure is resolved by the medium. We observe in this case a characteristic delay: the jet radiates as one color current (quark) up to the formation of the "hard" gluon, at which point we observe the onset of radiation of the new color current (gluon). Our computation supports a picture in which the in-medium jet dynamics are described as a collection of subsequent antennas which are resolved by the medium according to their transverse extent.

    hep-phhep-thnucl-thJHEP(2016)·32 citations
28. 28*

    A low-energy determination of ${\alpha }_s$ at three loops

    Antonio Vairo🇩🇪

    We review one of the most accurate low-energy determinations of ${\alpha }_s$. Comparing at short distances the QCD static energy at three loops and resummation of the next-to-next-to leading logarithms with its determination in 2+1-flavor lattice QCD, we obtain ${\alpha }_s(1.5\mathrm{GeV})=0.336_{-0.008}^{+0.012}$, which corresponds to ${\alpha }_s(M_Z)=0.1166_{-0.0008}^{+0.0012}$. We discuss future perspectives.

    hep-phhep-latEPJ Web Conf.(2016)·13 citations
29. 29*

    Scalar singlets at present and future colliders

    Dario Buttazzo🇨🇭

    A scalar singlet, coupled to the other particles only through its mixing with the Higgs boson, appears in several motivated extensions of the Standard Model. The prospects for the discovery of a generic singlet at the various stages of the LHC, as well as at future high-energy colliders, are studied, and the reach of direct searches is compared with the precision attainable with Higgs couplings measurements. The results are then applied to the NMSSM and Twin Higgs.

    hep-phFrascati Phys.Ser.(2016)·0 citations
30. 30*

    Searching for decaying dark matter in deep XMM-Newton observation of the Draco dwarf spheroidal

    Oleg Ruchayskiy🇩🇰 · Alexey Boyarsky🇳🇱 · Dmytro Iakubovskyi🇺🇦 · Esra Bulbul🇺🇸 · Dominique Eckert🇨🇭 · Jeroen Franse🇳🇱 · Denys Malyshev🇨🇭 · Maxim Markevitch🇺🇸 · Andrii Neronov🇨🇭

    We present results of a search for the 3.5 keV emission line in our recent very long (~ 1.4 Ms) XMM-Newton observation of the Draco dwarf spheroidal galaxy. The astrophysical X-ray emission from such dark matter-dominated galaxies is faint, thus they provide a test for the dark matter origin of the 3.5 keV line previously detected in other massive, but X-ray bright objects, such as galaxies and galaxy clusters. We do not detect a statistically significant emission line from Draco; this constrains the lifetime of a decaying dark matter particle to tau > (7-9) x 10^27 s at 95% CL (combining all three XMM-Newton cameras; the interval corresponds to the uncertainty of the dark matter column density in the direction of Draco). The PN camera, which has the highest sensitivity of the three, does show a positive spectral residual (above the carefully modeled continuum) at E = 3.54 +/- 0.06 keV with a 2.3 sigma significance. The two MOS cameras show less-significant or no positive deviations, consistently within 1 sigma with PN. Our Draco limit on tau is consistent with previous detections in the stacked galaxy clusters, M31 and the Galactic Center within their 1-2 sigma uncertainties, but is inconsistent with the high signal from the core of the Perseus cluster (which has itself been inconsistent with the rest of the detections). We conclude that this Draco observation does not exclude the dark matter interpretation of the 3.5 keV line in those objects.

    ↳ astro-ph.HEhep-phMNRAS(2016)·124 citations
31. 31*

    Probing BSM Neutrino Physics with Flavor and Spectral Distortions: Prospects for Future High-Energy Neutrino Telescopes

    Ian M. Shoemaker🇺🇸 · Kohta Murase🇺🇸

    The flavor of cosmic neutrinos may help unveil their sources and could reveal the presence of new physics in the neutrino sector. We consider the impacts of next-generation neutrino detectors, including the planned upgrade to neutrino detector--IceCube-Gen2, which is well-positioned to make dramatic improvements in both flavor and spectral measurements. We show that various models in neutrino physics beyond the Standard Model, such as neutrino decay, pseudo-Dirac states, and neutrino self-scattering, may be found or strongly constrained at IceCube-Gen2 and KM3NeT. We find that the additional flavor discriminants given by Glashow resonance events and so-called "double-bang" topologies improve the ability to access the flavor of the cosmic high-energy neutrinos and probe the BSM physics. In addition, although the details depend on source properties, Glashow resonance events have the additional feature of being able to inform us of the relative strengths of neutrino and antineutrino emission, which may help us discriminate astrophysical scenarios.

    ↳ astro-ph.HEhep-phPRD(2016)·145 citations
32. 32*

    Charge transport and vector meson dissociation across the thermal phase transition in lattice QCD with two light quark flavors

    Bastian B. Brandt🇩🇪 · Anthony Francis🇨🇦 · Benjamin Jaeger🇬🇧 · Harvey B. Meyer🇩🇪

    We compute and analyze correlation functions in the isovector vector channel at vanishing spatial momentum across the deconfinement phase transition in lattice QCD. The simulations are carried out at temperatures $T/T_c=0.156,0.8,1.0,1.25$ and $1.67$ with $T_c\simeq 203$MeV for two flavors of Wilson-Clover fermions with a zero-temperature pion mass of $\simeq 270$MeV. Exploiting exact sum rules and applying a phenomenologically motivated ansatz allows us to determine the spectral function $\rho (\omega ,T)$ via a fit to the lattice correlation function data. From these results we estimate the electrical conductivity across the deconfinement phase transition via a Kubo formula and find evidence for the dissociation of the $\rho$ meson by resolving its spectral weight at the available temperatures. We also apply the Backus-Gilbert method as a model-independent approach to this problem. At any given frequency, it yields a local weighted average of the true spectral function. We use this method to compare kinetic theory predictions and previously published phenomenological spectral functions to our lattice study.

    ↳ hep-lathep-phnucl-thPRD(2016)·94 citations
33. 33*

    Dark matter from gravitational particle production at reheating

    Tommi Markkanen🇬🇧 · Sami Nurmi🇫🇮

    We show that curvature induced particle production at reheating generates adiabatic dark matter if there are non-minimally coupled spectator scalars weakly coupled to visible matter. The observed dark matter abundance implies an upper bound on spectator masses $m$ and non-minimal coupling values $\xi$. For example, assuming quadratic inflation, instant reheating and a single spectator scalar with only gravitational couplings, the observed dark matter abundance is obtained for $m\sim 0.1$ GeV and $\xi \sim 1$. Larger mass and coupling values of the spectator are excluded as they would lead to overproduction of dark matter.

    ↳ astro-ph.COhep-phJCAP(2017)·75 citations
34. 34*

    Anisotropic hydrodynamics for conformal Gubser flow

    Michael Strickland🇺🇸 · Mohammad Nopoush🇺🇸 · Radoslaw Ryblewski🇵🇱

    In this proceedings contribution, we review the exact solution of the anisotropic hydrodynamics equations for a system subject to Gubser flow. For this purpose, we use the leading-order anisotropic hydrodynamics equations which assume that the distribution function is ellipsoidally symmetric in local-rest-frame momentum. We then prove that the SO(3)_q symmetry in de Sitter space constrains the anisotropy tensor to be of spheroidal form with only one independent anisotropy parameter remaining. As a consequence, the exact solution reduces to the problem of solving two coupled non-linear differential equations. We show that, in the limit that the relaxation time goes to zero, one obtains Gubser's ideal hydrodynamic solution and, in the limit that the relaxation time goes to infinity, one obtains the exact free streaming solution obtained originally by Denicol et al. For finite relaxation time, we solve the equations numerically and compare to the exact solution of the relaxation-time-approximation Boltzmann equation subject to Gubser flow. Using this as our standard, we find that anisotropic hydrodynamics describes the spatio-temporal evolution of the system better than all currently known dissipative hydrodynamics approaches.

    ↳ nucl-thhep-phNPA(2016)·24 citations
35. 35*

    Dark Matter Searches at the Large Hadron Collider

    Siew Yan Hoh🇲🇾 · Jyothsna Komaragiri🇲🇾 · Wan Ahmad Tajuddin Bin Wan Abdullah🇲🇾

    Dark Matter is a hypothetical particle proposed to explain the missing matter expected from the cosmological observation. The motivation of Dark Matter is overwhelming however as it is mainly deduced from its gravitational interaction, for it does little to pinpoint what Dark Matter really is. In WIMPs Miracle, weakly interactive massive particle being the Dark Matter candidate is correctly producing the current thermal relic density at weak scale, implying the possibility of producing and detecting it in Large Hadron Collider. Assuming WIMPs being the maverick particle within collider, it is expected to be pair produced in association with a Standard Model particle. The presence of the WIMPs pair is inferred from the Missing Transverse Energy (MET) which is the vector sum of the imbalance in the transverse momentum plane recoils a Standard Model Particle. The collider is able to produce light mass Dark Matter which the traditional detection fail to detect due to the small momentum transfer involved in the interaction; on the other hand, the traditional detection is robust in detecting a higher Dark matter masses but the collider is su ered from the parton distribution function suppression. Topologically the processes are similar to the scattering processes in the direct detection thus complementary to the traditional Dark Matter detection. The collider searches are strongly motivated as the results are usually translated to the annihilation and scattering rates at more traditional Dark Matter-oriented experiments, thus a concordance approach is adapted. An overview of Dark Matter searches at the Large Hadron Collider will be covered in this paper.

    ↳ hep-exhep-phAIP Conf.Proc.(2016)·6 citations
36. 36*

    Unified description of electron-nucleus scattering within the spectral function formalism

    Noemi Rocco🇮🇹 · Alessandro Lovato🇺🇸 · Omar Benhar🇮🇹

    We developed a novel approach based on a generalization of factorization and nuclear spectral functions, allowing for a consistent treatment of the amplitudes involving one- and two-nucleon currents, whose contribution to the nuclear electromagnetic response in the transverse channel is known to be significant. We report the results of calculations of the inclusive electron-carbon cross section, showing that the inclusion of processes involving two-nucleon currents appreciably improves the agreement between theory and data in the dip region, between the quasi elastic and $\Delta$-production peaks. The implications for the analysis of neutrino-nucleus cross sections are discussed.

    ↳ nucl-thhep-exhep-phPRL(2016)·97 citations
37. 37*

    Comments on the nilpotent constraint of the goldstino superfield

    D. M. Ghilencea🇷🇴

    Superfield constraints were often used in the past, in particular to describe the Akulov-Volkov action of the goldstino by a superfield formulation with $L=({\Phi }^{†}\Phi {)}_D+[(f\Phi {)}_F+h.c.]$ endowed with the nilpotent constraint ${\Phi }^2=0$ for the goldstino superfield ($\Phi$). Inspired by this, such constraint is often used to define the goldstino superfield even in the presence of additional superfields, for example in models of "nilpotent inflation". In this review we show that the nilpotent property is not valid in general, under the assumption of a microscopic (ultraviolet) description of the theory with linear supermultiplets. Sometimes only weaker versions of the nilpotent relation are true such as ${\Phi }^3=0$ or ${\Phi }^4=0$ (${\Phi }^2\ne 0$) in the infrared (far below the UV scale) under the further requirement of decoupling all additional scalars (coupling to sgoldstino), something not always possible (e.g. if light scalars exist). In such cases the weaker nilpotent property is not specific to the goldstino superfield anymore. We review the restrictions for the Kahler curvature tensor and superpotential $W$ under which ${\Phi }^2=0$ remains true in infrared, assuming linear supermultiplets in the microscopic description. One can reverse the arguments to demand that the nilpotent condition, initially an infrared property, be extended even in the presence of additional superfields, but this may question the nature of supersymmetry breaking or the existence of a perturbative ultraviolet completion with linear supermultiplets.

    ↳ hep-thhep-phMod.Phys.Lett.A(2016)·14 citations
38. 38*

    Echoes of Inflationary First-Order Phase Transitions in the CMB

    Hongliang Jiang🇨🇳 · Tao Liu🇨🇳 · Sichun Sun🇨🇳 · Yi Wang🇨🇳

    Cosmological phase transitions (CPTs), such as the Grand Unified Theory (GUT) and the electroweak (EW) ones, play a significant role in both particle physics and cosmology. In this letter, we propose to probe the first-order CPTs, by detecting gravitational waves (GWs) which are generated during the phase transitions through the cosmic microwave background (CMB). If happened around the inflation era, the first-order CPTs may yield low-frequency GWs due to bubble dynamics, leaving imprints on the CMB. In contrast to the nearly scale-invariant primordial GWs caused by vacuum fluctuation, these bubble-generated GWs are scale dependent and have non-trivial B-mode spectra. If decoupled from inflaton, the EWPT during inflation may serve as a probe for the one after reheating where the baryon asymmetry could be generated via EW baryogenesis (EWBG). The CMB thus provides a potential way to test the feasibility of the EWBG, complementary to the collider measurements of Higgs potential and the direct detection of GWs generated during EWPT.

    ↳ astro-ph.COhep-phhep-thPLB(2017)·30 citations
39. 39*

    Constraints on four-fermion interactions from the $t\bar{t}$ charge asymmetry at hadron colliders

    Martin Perello Rosello🇪🇸 · Marcel Vos🇪🇸

    The charge asymmetry in top quark production at hadron colliders is sensitive to beyond-the-Standard-Model four-fermion interactions. In this study we compare the sensitivity of cross-section and charge asymmetry measurements to effective operators describing four-fermion interactions and study the limits on the validity of this approach. A fit to a combination of Tevatron and LHC measurements yields stringent limits on the linear combinations $C_1$ and $C_2$ of the four-fermion effective operators.

    ↳ hep-exhep-phEPJC(2016)·39 citations
40. 40*

    A supersymmetric Skyrme model

    Sven Bjarke Gudnason🇨🇳 · Muneto Nitta🇯🇵 · Shin Sasaki🇯🇵

    Construction of a supersymmetric extension of the Skyrme term was a long-standing problem because of the auxiliary field problem; that is, the auxiliary field may propagate and cannot be eliminated, and the problem of having fourth-order time derivative terms. In this paper, we construct for the first time a supersymmetric extension of the Skyrme term in four spacetime dimensions, in the manifestly supersymmetric superfield formalism that does not suffer from the auxiliary field problem. Chiral symmetry breaking in supersymmetric theories results not only in Nambu-Goldstone (NG) bosons (pions) but also in the same number of quasi-NG bosons so that the low-energy theory is described by an SL(N,C)-valued matrix field instead of SU(N) for NG bosons. The solution of auxiliary fields is trivial on the canonical branch of the auxiliary field equation, in which case our model results in a fourth-order derivative term that is not the Skyrme term. For the case of SL(2,C), we find explicitly a nontrivial solution to the algebraic auxiliary field equations that we call a non-canonical branch, which when substituted back into the Lagrangian gives a Skyrme-like model. If we restrict to a submanifold, where quasi-NG bosons are turned off, which is tantamount to restricting the Skyrme field to SU(2), then the fourth-order derivative term reduces exactly to the standard Skyrme term. Our model is the first example of a nontrivial auxiliary field solution in a multi-component model.

    ↳ hep-thhep-phJHEP(2016)·42 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.