Tue·Mar 8, 2016Tuesday·March 8, 2016

1. 01*

   Exploring high-mass diphoton resonance without new colored states

   Amine Ahriche🇩🇿 · Gaber Faisel🇹🇼 · Salah Nasri🇦🇪 · Jusak Tandean🇹🇼

   A new heavy resonance may be observable at the LHC if it has a significant decay branching fraction into a pair of photons. We entertain this possibility by looking at the modest excess in the diphoton invariant mass spectrum around 750 GeV recently reported in the ATLAS and CMS experiments. Assuming that it is a spinless boson, dubbed $\tilde{s}$, we consider it within a model containing two weak scalar doublets having zero vacuum expectation values and a scalar singlet in addition to the doublet responsible for breaking the electroweak symmetry. The model also possesses three Dirac neutral singlet fermions, the lightest one of which can play the role of dark matter and which participate with the new doublet scalars in generating light neutrino masses radiatively. We show that the model is consistent with all phenomenological constraints and can yield a production cross section $\sigma (pp\to \tilde{s}\to \gamma \gamma )$ of roughly the desired size, mainly via the photon-fusion contribution, without involving extra colored fermions or bosons. We also discuss other major decay modes of $\tilde{s}$ which are potentially testable in upcoming LHC measurements.

   hep-phhep-exNPB(2017)·16 citations
2. 02*

   NNLOPS accurate associated HW production

   William Astill🇬🇧 · Wojciech Bizon🇬🇧 · Emanuele Re🇬🇧 · Giulia Zanderighi🇨🇭

   We present a next-to-next-to-leading order accurate description of associated HW production consistently matched to a parton shower. The method is based on reweighting events obtained with the HW plus one jet NLO accurate calculation implemented in POWHEG, extended with the MiNLO procedure, to reproduce NNLO accurate Born distributions. Since the Born kinematics is more complex than the cases treated before, we use a parametrization of the Collins-Soper angles to reduce the number of variables required for the reweighting. We present phenomenological results at 13 TeV, with cuts suggested by the Higgs Cross Section Working Group.

   hep-phhep-exJHEP(2016)·69 citations
3. 03*

   Searching for supersymmetry scalelessly

   Matthias Schlaffer🇮🇱 · Michael Spannowsky🇬🇧 · Andreas Weiler🇩🇪

   In this paper we propose a scale invariant search strategy for hadronic top or bottom plus missing energy final states. We present a method which shows flat efficiencies and background rejection factors over broad ranges of parameters and masses. The resulting search can be easily recast into a limit on alternative models. We show the strength of the method in a natural SUSY setup where stop and sbottom squarks are pair produced and decay into hadronically decaying top quarks or bottom quarks and higgsinos.

   hep-phhep-exEPJC(2016)·6 citations
4. 04*

   The 750 GeV diphoton excess in unified $SU(2{)}_L\times SU(2{)}_R\times SU(4)$ models from noncommutative geometry

   Ufuk Aydemir🇸🇪 · Djordje Minic🇺🇸 · Chen Sun🇺🇸 · Tatsu Takeuchi🇺🇸

   We discuss a possible interpretation of the $750$ GeV diphoton resonance, recently reported at the LHC, within a class of $SU(2{)}_L\times SU(2{)}_R\times SU(4)$ models with gauge coupling unification. The unification is imposed by the underlying non-commutative geometry (NCG), which in these models is extended to a left-right symmetric completion of the Standard Model (SM). Within such \textit{unified} $SU(2{)}_L\times SU(2{)}_R\times SU(4)$ models the Higgs content is restrictively determined from the underlying NCG, instead of being arbitrarily selected. We show that the observed cross sections involving the $750$ GeV diphoton resonance could be realized through a SM singlet scalar field accompanied by colored scalars, present in these unified models. In view of this result we discuss the underlying rigidity of these models in the NCG framework and the wider implications of the NCG approach for physics beyond the SM.

   hep-phMod.Phys.Lett.A(2016)·25 citations
5. 05*

   R-parity Conserving Minimal SUSY $B-L$ Model

   Nobuchika Okada🇺🇸 · Nathan Papapietro🇺🇸

   We propose a simple gauged U(1)${}_{B-L}$ extension of the minimal supersymmetric Standard Model (MSSM), where R-parity is conserved as usual in the MSSM. The global $B-L$ (baryon number minus lepton number) symmetry in the MSSM is gauged and three MSSM gauge-singlet chiral multiplets with a unit $B-L$ charge are introduced, ensuring the model free from gauge and gravitational anomalies. We assign an odd R-parity for two of the new chiral multiplets and hence they are identified with the right-handed neutrino superfields, while an even R-parity is assigned to the other one ($\Phi$). The scalar component of $\Phi$ plays the role of a Higgs field to break the U(1)${}_{B-L}$ symmetry through its negative mass squared, which is radiatively generated by the renormalization group running of soft supersymmetry (SUSY) breaking parameters from a high energy. This radiative U(1)${}_{B-L}$ symmetry breaking leads to its breaking scale being at the TeV naturally. Because of our novel R-parity assignment, three light neutrinos are Dirac particles with one massless state. Since R-parity is conserved, the lightest neutralino is a prime candidate of the dark matter as usual. In our model, the lightest eigenstate of the mixture of the $B-L$ gaugino and the fermionic component of $\Phi$ appears as a new dark matter candidate. We investigate phenomenology of this dark matter particle. We also discuss collider phenomenology of our model. In particular, the $B-L$ gauge boson ($Z^{\prime }$), once discovered at the Large Hadron Collider, can be a probe to determine the number of (right-handed) Dirac neutrinos with its invisible decay width, in sharp contrast with the conventional $B-L$ extension of the SM or MSSM where the right-handed neutrinos are heavy Majorana particles and decay to the SM leptons.

   hep-ph8 citations
6. 06*

   Combined heavy-quark symmetry and large-$N_c$ operator analysis for 2-body counterterms in the chiral Lagrangian with $D$ mesons and charmed baryons

   Daris Samart🇹🇭 · Chakrit Nualchimplee🇹🇭 · Yupeng Yan🇹🇭

   We construct, in the work, chiral $SU(3)$ Lagrangian with $D$ mesons of spin $J^P=0^{-}$ and $J^P=1^{-}$ and charmed baryons of spin $J^P=1/2^{+}$ and $J^P=3/2^{+}$. There are 42 leading two-body counter-terms involving two charmed baryon fields and two $D$ meson fields in the constructed Lagrangian. The heavy-quark spin symmetry leads to 35 sum rules while the large-$N_c$ operator analysis predicts 29 ones at the next-to leading order of $1/N_c$ expansion. The combination of the sum rules from both the heavy-quark symmetry and the large-$N_c$ analysis results in 38 independent sum rules which reduces the number of free parameters in the chiral Lagrangian down to 4 only. This is a remarkable result demonstrating the consistency of the heavy-quark symmetry and large-$N_c$ operator analysis.

   hep-phPRD(2016)·2 citations
7. 07*

   Nuclear effects in Drell-Yan pair production in high-energy $pA$ collisions

   Eduardo Basso🇧🇷 · Victor P. Goncalves🇧🇷 · Michal Krelina🇨🇿 · Jan Nemchik🇸🇰 · Roman Pasechnik🇸🇪

   The Drell-Yan (DY) process of dilepton pair production off nuclei is not affected by final state interactions, energy loss or absorption. A detailed phenomenological study of this process is thus convenient for investigation of the onset of initial-state effects in proton-nucleus ($pA$) collisions. In this paper, we present a comprehensive analysis of the DY process in $pA$ interactions at RHIC and LHC energies in the color dipole framework. We analyse several effects affecting the nuclear suppression, $R_{pA}<1$, of dilepton pairs, such as the saturation effects, restrictions imposed by energy conservation (the initial-state effective energy loss) and the gluon shadowing, as a function of the rapidity, invariant mass of dileptons and their transverse momenta $p_T$. In this analysis, we take into account besides the ${\gamma }^{\ast }$ also the $Z^0$ contribution to the production cross section, thus extending the predictions to large dilepton invariant masses. Besides the nuclear attenuation of produced dileptons at large energies and forward rapidities emerging due to the onset of shadowing effects, we predict a strong suppression at large $p_T$, dilepton invariant masses and Feynman $x_F$ caused by the Initial State Interaction effects in kinematic regions where no shadowing is expected. The manifestations of nuclear effects are investigated also in terms of the correlation function in azimuthal angle between the dilepton pair and a forward pion $\Delta \varphi$ for different energies, dilepton rapidites and invariant dilepton masses. We predict that the characteristic double-peak structure of the correlation function around $\Delta \varphi \simeq \pi$ arises for very forward pions and large-mass dilepton pairs.

   hep-phPRD(2016)·19 citations
8. 08*

   Parton distribution functions probed in ultraperipheral collisions at the CERN Large Hadron Collider

   J. Thomas🇺🇸 · C.A. Bertulani🇺🇸 · N. Brady🇺🇸 · D. B. Clark🇺🇸 · E. Godat🇺🇸 · F. Olness🇺🇸

   Vector meson production in ultra-peripheral pA and AA collisions at the CERN Large Hadron Collider (LHC) are very sensitive to Parton Distribution Functions (PDF) as well as to their leading-order, next-to-leading-order, and medium corrections. This process is a complimentary tool to explore the effects of different PDFs in particle production in proton-nucleus and nucleus-nucleus central collisions. Existing and forthcoming data available, e.g., from ALICE and CMS, may be used in conjunction with our theoretical predictions to constrain the PDFs. We make predictions for rapidity distributions and for cross sections of J/$\psi$ , $\psi (2S)$ and ${\rm Y}$ production at $\sqrt{s_{NN}}=2.76$ TeV and $\sqrt{s_{NN}}=5$ TeV. We use the second energy as representative for the Run 2 of PbPb collisions at the LHC.

   hep-phnucl-th4 citations
9. 09*

   Full jet evolution in quark-gluon plasma and nuclear modification of jet production and jet shape in Pb+Pb collisions at 2.76 ATeV at the LHC

   Ning-Bo Chang🇨🇳 · Guang-You Qin🇨🇳

   We study the evolution of full jet shower in quark-gluon plasma via solving a set of coupled differential transport equations for the three-dimensional momentum distributions of quarks and gluons contained in the full jets. In our jet evolution equations, we include all partonic splitting processes as well as the collisional energy loss and transverse momentum broadening for both the leading and radiated partons of the full jets. Combining with a realistic (2+1)-dimensional viscous hydrodynamic simulation for the space-time profiles of the hot and dense nuclear medium produced in heavy-ion collisions, we apply our formalism to calculate the nuclear modification of single inclusive full jet spectra, the momentum imbalance of photon-jet and dijet pairs, and jet shape function (at partonic level) in Pb+Pb collisions at 2.76 ATeV. The roles of various jet-medium interaction mechanisms on the full jet modification are studied. We find that the nuclear modification of jet shape is sensitive to the interplay of different interaction mechanisms as well as the energies of the full jets.

   hep-phnucl-exnucl-thPRC(2016)·77 citations
10. 10*

    Estimating transport coefficients in hot and dense quark matter

    Paramita Deb🇮🇳 · Guru Prakash Kadam🇮🇳 · Hiranmaya Mishra🇮🇳

    We compute the transport coefficients, namely, the coefficients of shear and bulk viscosity as well as thermal conductivity for hot and dense quark matter. The calculations are performed within the Nambu- Jona Lasinio (NJL) model. The estimation of the transport coefficients is made using a quasiparticle approach of solving the Boltzmann kinetic equation within the relaxation time approximation. The transition rates are calculated in a manifestly covariant manner to estimate the thermal-averaged cross sections for quark-quark and quark-antiquark scattering. The calculations are performed for finite chemical potential also. Within the parameters of the model, the ratio of shear viscosity to entropy density has a minimum at the Mott transition temperature. At vanishing chemical potential, the ratio of bulk viscosity to entropy density, on the other hand, decreases with temperature with a sharp decrease near the critical temperature, and vanishes beyond it. At finite chemical potential, however, it increases slowly with temperature beyond the Mott temperature. The coefficient of thermal conductivity also shows a minimum at the critical temperature.

    hep-phnucl-thPRD(2016)·69 citations
11. 11*

    Identifying the production process of new physics at colliders; symmetric or asymmetric?

    Sung Hak Lim🇰🇷

    We propose a class of kinematic variables, which is a smooth generalization of min-max type mass variables such as the Cambridge-$M_{T2}$ and $M_2$, for measuring a mass spectrum of intermediate resonances in a semi-invisibly decaying pair production. While kinematic endpoints of min-max type mass variables are only sensitive to a heavier resonance mass, kinematic endpoints of new variables are sensitive to all masses. These new mass variables can be used to resolve a mass spectrum, so that if the true mass spectrum is asymmetric, then the kinematic endpoints are separate while the endpoints are the same for the symmetric true mass spectrum. We demonstrate the behavior of kinematic endpoint of these new variables in pair production of two-body and three-body decays with one invisible particle.

    hep-phJHEP(2016)·4 citations
12. 12*

    Model discrimination in pseudoscalar-meson photoproduction

    J. Nys🇧🇪 · J. Ryckebusch🇧🇪 · D. G. Ireland🇬🇧 · D. I. Glazier🇬🇧

    To learn about a physical system of interest, experimental results must be able to discriminate among models. We introduce a geometrical measure to quantify the distance between models for pseudoscalar-meson photoproduction in amplitude space. Experimental observables, with finite accuracy, map to probability distributions in amplitude space, and the characteristic width scale of such distributions needs to be smaller than the distance between models if the observable data are going to be useful. We therefore also introduce a method for evaluating probability distributions in amplitude space that arise as a result of one or more measurements, and show how one can use this to determine what further measurements are going to be necessary to be able to discriminate among models.

    hep-phnucl-thPLB(2016)·15 citations
13. 13*

    Analytical approximations for matter effects on CP violation in the accelerator-based neutrino oscillations with E \lesssim 1 GeV

    Zhi-zhong Xing🇨🇳 · Jing-yu Zhu🇨🇳

    Given an accelerator-based neutrino experiment with the beam energy E \lesssim 1 GeV, we expand the probabilities of \nu_\mu \to \nu_e and \overline {\nu}_\mu \to \overline {\nu}_e oscillations in matter in terms of two small quantities \Delta_{21}/\Delta_{31} and A/\Delta_{31}, where \Delta_{21} \equiv m^2_2 - m^2_1 and \Delta_{31} \equiv m^2_3 - m^2_1 are the neutrino mass-squared differences, and A measures the strength of terrestrial matter effects. Our analytical approximations are numerically more accurate than those made by Freund in this energy region, and thus they are particularly applicable for the study of leptonic CP violation in the low-energy MOMENT, ESS\nuSM and T2K oscillation experiments. As a by-product, the new analytical approximations help us to easily understand why the matter-corrected Jarlskog parameter \widetilde{\cal J} peaks at the resonance energy E_* \simeq 0.14 GeV (or 0.12 GeV) for the normal (or inverted) neutrino mass hierarchy, and how the three Dirac unitarity triangles are deformed due to the terrestrial matter contamination. We also affirm that a medium-baseline neutrino oscillation experiment with the beam energy E lying in the E_* \lesssim E \lesssim 2 E_* range is capable of exploring leptonic CP violation with little matter-induced suppression.

    hep-phhep-exJHEP(2016)·27 citations
14. 14*

    $D$-Wave Charmonia ${\eta }_{c2}$($1{}^1{D}_2$), ${\psi }_2$($1{}^3{D}_2$), and ${\psi }_3$($1{}^3{D}_3$) in $B_c$ Decays

    Qiang Li🇨🇳 · Tianhong Wang🇨🇳 · Yue Jiang🇨🇳 · Han Yuan🇨🇳 · Guo-Li Wang🇨🇳

    We study the semi-leptonic and non-leptonic decays of $B_c$ meson to $D$-wave charmonia, namely, ${\eta }_{c2}(1^1{D}_2)$, ${\psi }_2(1^3{D}_2)$, and ${\psi }_3(1^3{D}_3)$. In our calculations, the instantaneous Bethe-Salpeter method is applied to achieve the hadronic matrix elements. This method includes relativistic corrections which are important especially for the higher orbital excited states. For the semi-leptonic decay channels with electron as the final lepton, we get the branching ratios $\mathcal{B}[B_c\to {\eta }_{c2}e{\bar{\nu }}_e]=5.9_{+1.0}^{-0.8}\times 10^{-4}$, $\mathcal{B}[B_c\to {\psi }_{2}e{\bar{\nu }}_e]=1.5_{+0.3}^{-0.2}\times 10^{-4}$, and $\mathcal{B}[B_c\to {\psi }_{3}e{\bar{\nu }}_e]=3.5_{+0.8}^{-0.6}\times 10^{-4}$. The transition form factors, forward-backward asymmetries, and lepton spectra in these processes are also presented. For the non-leptonic decay channels, those with $\rho$ as the lighter meson have the largest branching ratios, $\mathcal{B}[B_c\to {\eta }_{c2}\rho ]=8.1_{+1.0}^{-1.0}\times 10^{-4}$, $\mathcal{B}[B_c\to {\psi }_2\rho ]=9.6_{+1.0}^{-1.0}\times 10^{-5}$, and $\mathcal{B}[B_c\to {\psi }_3\rho ]=4.1_{+0.8}^{-0.7}\times 10^{-4}$.

    hep-phhep-exEPJC(2016)·15 citations
15. 15*

    Little Higgs after the little one

    Debajyoti Choudhury🇮🇳 · Dilip Kumar Ghosh🇮🇳 · Santosh Kumar Rai🇮🇳 · Ipsita Saha🇮🇳

    At the LHC, the Littlest Higgs Model with $T$-parity is characterised by various production channels. If the $T$-odd quarks are heavier than the exotic partners of the $W$ and the $Z$, then associated production can be as important as the pair-production of the former. Studying both, we look for final states comprising at least one lepton, jets and missing transverse energy. We consider all the SM processes that could conspire to contribute as background to our signals, and perform a full detector level simulation of the signal and background to estimate the discovery potential at the current run as well as at the scheduled upgrade of the LHC. We also show that, for one of the channels, the reconstruction of two tagged $b$-jets at the Higgs mass $(M_h=125\mathrm{GeV})$ provides us with an unambiguous hint for this model.

    hep-phhep-exJHEP(2016)·3 citations
16. 16*

    Quality of the Peccei-Quinn symmetry in the Aligned QCD Axion and Cosmological Implications

    Tetsutaro Higaki🇯🇵 · Kwang Sik Jeong🇰🇷 · Naoya Kitajima🇰🇷 · Fuminobu Takahashi🇯🇵

    We show that the required high quality of the Peccei-Quinn symmetry can be naturally explained in the aligned QCD axion models where the QCD axion arises from multiple axions with decay constants much smaller than the axion window, e.g., around the weak scale. Even in the presence of general Planck-suppressed Peccei-Quinn symmetry breaking operators, the effective strong CP phase remains sufficiently small in contrast to the standard axion models without the alignment. The QCD axion potential has small or large modulations due to the symmetry breaking operators, which can significantly affect the axion cosmology. When the axions are trapped in different minima, domain walls appear and their scaling behavior suppresses the axion isocurvature perturbations at super-horizon scales. Our scenario predicts many axions and saxions coupled to gluons, and they may be searched for at collider experiments. In particular, the recently found diphoton excess at 750 GeV could be due to one of such (s)axions.

    hep-phJHEP(2016)·86 citations
17. 17*

    CGC/saturation approach for high energy soft interactions: ${\mathbf{v}}_2$ in proton-proton collisions

    E. Gotsman (Tel Aviv U.)🇮🇱 · E. Levin (Tel Aviv U./UTFSM)🇮🇱 · U. Maor (Tel Aviv U.)🇮🇱 · S.Tapia (UTFSM)🇨🇱

    In this paper we continue our program to construct a model for high energy soft interactions, based on the CGC/saturation approach. We demonstrate that in our model which describes diffractive physics as well as multi-particle production at high energy, the density variation mechanism leads to the value of $v_2$ which is about $60\%÷70\%$ of the measured $v_2$. Bearing in mind that in CGC/saturation approach there are two other mechanisms present: Bose enhancement in the wave function and local anisotropy, we believe that the azimuthal long range rapidity correlations in proton-proton collisions stem from the CGC/saturation physics, and not from quark-gluon plasma production.

    hep-phPRD(2016)·12 citations
18. 18*

    Couplings between QCD axion and photon from string compactification

    Jihn E. Kim

    The QCD axion couplings of various invisible axion models are presented. In particular, the exact global symmetry U(1)${}_{\mathrm{PQ}}$ in the superpotential is possible for the anomalous U(1) from string compactification, broken only by the gauge anomalies at one loop level, and is shown to have the resultant invisible axion coupling to photon, $c_{a\gamma \gamma }\ge \frac{8}{3}-c_{a\gamma \gamma }^{\mathrm{ch}\mathrm{br}}$ where $c_{a\gamma \gamma }^{\mathrm{ch}\mathrm{br}}\simeq 2$. However, this bound is not applicable in approximate U(1)${}_{\mathrm{PQ}}$ models with sufficiently suppressed U(1)${}_{\mathrm{PQ}}$-breaking superpotential terms. We also present a simple method to obtain $c_{a\gamma \gamma }^0$ which is the value obtained above the electroweak scale.

    hep-phastro-ph.COhep-thPLB(2016)·8 citations
19. 19*

    Functional renormalization group analysis of the soft mode at the QCD critical point

    Takeru Yokota🇯🇵 · Teiji Kunihiro🇯🇵 · Kenji Morita🇯🇵

    We make an intensive investigation of the soft mode at the quantum chromodynamics (QCD) critical point on the basis of the functional renormalization group (FRG) method in the local potential approximation. We calculate the spectral functions ${\rho }_{\sigma ,\pi }(\omega ,p)$ in the scalar ($\sigma$) and pseudoscalar ($\pi$) channels beyond the random phase approximation in the quark--meson model. At finite baryon chemical potential $\mu$ with a finite quark mass, the baryon-number fluctuation is coupled to the scalar channel and the spectral function in the $\sigma$ channel has a support not only in the time-like ($\omega >p$) but also in the space-like ($\omega <p$) regions, which correspond to the mesonic and the particle--hole phonon excitations, respectively. We find that the energy of the peak position of the latter becomes vanishingly small with the height being enhanced as the system approaches the QCD critical point, which is a manifestation of the fact that the phonon mode is the {\em soft mode} associated with the second-order transition at the QCD critical point, as has been suggested by some authors. Moreover, our extensive calculation of the spectral function in the $(\omega ,p)$ plane enables us to see that the mesonic and phonon modes have the respective definite dispersion relations ${\omega }_{\sigma .\mathrm{ph}}(p)$, and it turns out that ${\omega }_{\sigma }(p)$ crosses the light-cone line into the space-like region, and then eventually merges into the phonon mode as the system approaches the critical point more closely. This implies that the sigma-mesonic mode also becomes soft at the critical point. We also provide numerical stability conditions that are necessary for obtaining the accurate effective potential from the flow equation.

    hep-phnucl-thPTEP(2016)·42 citations
20. 20*

    Implications of lepton flavour violation on long baseline neutrino oscillation experiments

    C Soumya · R. Mohanta🇮🇳

    Non-standard neutrino interactions (NSIs), the sub-leading effects in the flavour transitions of neutrinos, play a crucial role in the determination of the various unknowns in neutrino oscillations, such as neutrino mass hierarchy, Dirac CP violating phase and the octant of atmospheric mixing angle. In this work, we focus on the possible implications of lepton flavour violating (LFV) NSIs, which generally affect the neutrino propagation, on the determination of the these unknown oscillation parameters. We study the effect of these NSIs on the physics potential of the currently running and upcoming long-baseline experiments, i.e., T2K, NO$\nu$A and DUNE. We also check the allowed oscillation parameter space in presence of LFV NSIs.

    hep-phPRD(2016)·20 citations
21. 21*

    SeeSaw scale discrete dark matter and two-zero texture Majorana neutrino mass matrices

    J. M. Lamprea🇲🇽 · E. Peinado🇲🇽

    In this paper we present a scenario where the stability of dark matter and the phenomenology of neutrinos are related by the spontaneous breaking of a non-Abelian flavor symmetry. In this scenario the breaking is done at the seesaw scale, in such a way that what remains of the flavor symmetry is a Z2 symmetry, which stabilizes the dark matter. We have proposed two models based on this idea, for which we have calculated their neutrino mass matrices achieving two-zero texture in both cases. Accordingly, we have updated this two-zero texture phenomenology finding an interesting correlation between the reactor mixing angle and the sum of the light neutrino masses. We also have a correlation between the lightest neutrino mass and the neutrinoless double beta decay effective mass, obtaining a lower bound for the effective mass within the region of the nearly future experimental sensitivities.

    hep-phPRD(2016)·24 citations
22. 22*

    Interpreting 750 GeV Diphoton Excess in Plain NMSSM

    Marcin Badziak🇵🇱 · Marek Olechowski🇵🇱 · Stefan Pokorski🇵🇱 · Kazuki Sakurai🇬🇧

    NMSSM has enough ingredients to explain the diphoton excess at 750 GeV: singlet-like (pseudo) scalar ($a$) $s$ and higgsinos as heavy vector-like fermions. We consider the production of the 750 GeV singlet-like pseudo scalar a from a decay of the doublet-like pseudo scalar $A$, and the subsequent decay of $a$ into two photons via higgsino loop. We demonstrate that this cascade decay of the NMSSM Higgs bosons can explain the diphoton excess in the 13 TeV data consistently with the absence of a significant excess in the 8 TeV data.

    hep-phhep-exPLB(2016)·33 citations
23. 23*

    Search for Physics beyond Standard Model at the Precision Frontiers

    A. Aleksejevs🇨🇦 · S. Wu🇨🇭 · S. Barkanova🇨🇦 · Y. Bystritskiy🇷🇺 · V. Zykunov🇧🇾

    The article outlines the recent developments in the theoretical and computational approaches to the higher-order electroweak effects needed for the accurate interpretation of MOLLER and Belle II experimental data, and shows how new-physics particles enter at the one-loop level. By analyzing the effects of $Z^{\prime }$-boson on the polarization asymmetry, we show how this hypothetical interaction carrier may influence the future experimental results.

    hep-phJ.Phys.Conf.Ser.(2016)·1 citation
24. 24*

    Web matrices: structural properties and generating combinatorial identities

    Mark Dukes🇬🇧 · Chris D. White🇬🇧

    In this paper we present new results for the combinatorics of web diagrams and web worlds. These are discrete objects that arise in the physics of calculating scattering amplitudes in non-abelian gauge theories. Web-colouring and web-mixing matrices (collectively known as web matrices) are indexed by ordered pairs of web-diagrams and contain information relating the number of colourings of the first web diagram that will produce the second diagram. We introduce the black diamond product on power series and show how it determines the web-colouring matrix of disjoint web worlds. Furthermore, we show that combining known physical results with the black diamond product gives a new technique for generating combinatorial identities. Due to the complicated action of the product on power series, the resulting identities appear highly non-trivial. We present two results to explain repeated entries that appear in the web matrices. The first of these shows how diagonal web matrix entries will be the same if the comparability graphs of their associated decomposition posets are the same. The second result concerns general repeated entries in conjunction with a flipping operation on web diagrams. We present a combinatorial proof of idempotency of the web-mixing matrices, previously established using physical arguments only. We also show how the entries of the square of the web-colouring matrix can be achieved by a linear transformation that maps the standard basis for formal power series in one variable to a sequence of polynomials. We look at one parameterized web world that is related to indecomposable permutations and show how determining the web-colouring matrix entries in this case is equivalent to a combinatorics on words problem.

    ↳ math.COhep-phhep-thElectron. J. Combin. 23 (2016), no. 1, #P…·12 citations
25. 25*

    On the breaking of statistical isotropy through inflationary relics

    Juan C. Bueno Sánchez🇨🇴

    In this talk we elaborate on a mechanism to generate local contributions to the curvature perturbation in isolated patches of the Cosmic Microwave Background (CMB). The mechanism, based on the generation of an out-of-equilibrium configuration in fluctuating scalar fields of mass $m\sim H$ during a sustained stage of fast-roll inflation, has been recently shown to be capable of accounting for some of the most robust large-angle anomalies detected in the CMB. In this talk, we show in detail how the embedding of the mechanism into models including vector fields can result in the breaking of statistical isotropy in isolated patches of the CMB.

    ↳ astro-ph.COgr-qchep-phhep-thMod.Phys.Lett.A(2016)·0 citations
26. 26*

    Separation of elastic and inelastic processes in the relaxation time approximation for collision integral

    Wojciech Florkowski🇵🇱 · Radoslaw Ryblewski🇵🇱

    We introduce a generalised relaxation-time-approximation form of the collision term in the Boltzmann kinetic equation that allows for using different relaxation times for elastic and inelastic collisions. The efficacy of the proposed framework is demonstrated with the numerical calculations that describe systems with different relations between the two relaxation times and the evolution time of the system.

    ↳ nucl-thhep-phPRC(2016)·25 citations
27. 27*

    Electromagnetic radiation of charged particles in stochastic motion

    Tiberiu Harko🇬🇧 · Gabriela Mocanu🇷🇴

    The study of the Brownian motion of a charged particle in electric and magnetic fields fields has many important applications in plasma and heavy ions physics, as well as in astrophysics. In the present paper we consider the electromagnetic radiation properties of a charged non-relativistic particle in the presence of electric and magnetic fields, of an exterior non-electromagnetic potential, and of a friction and stochastic force, respectively. We describe the motion of the charged particle by a Langevin and generalized Langevin type stochastic differential equation. We investigate in detail the cases of the Brownian motion with or without memory in a constant electric field, in the presence of an external harmonic potential, and of a constant magnetic field. In all cases the corresponding Langevin equations are solved numerically, and a full description of the spectrum of the emitted radiation and of the physical properties of the motion is obtained. The Power Spectral Density (PSD) of the emitted power is also obtained for each case, and, for all considered oscillating systems, it shows the presence of peaks, corresponding to certain intervals of the frequency.

    ↳ astro-ph.HEhep-phnlin.CDEPJC(2016)·5 citations
28. 28*

    A Unified picture of Dark Matter and Dark Energy from Invisible QCD

    Andrea Addazi🇮🇹 · Antonino Marciano🇨🇳 · Stephon Alexander🇺🇸

    It has been shown in a companion paper that the late time acceleration of the universe can be accounted for by an extension of the QCD color to a $SU(3)$ invisible sector (IQCD). In this work we discuss a unified framework such the scale of dark chiral-breaking dictates both the accelerated expansion of the universe, and the origin of dark matter. We find that the strong and gravitational dynamics of dark quarks and gluons evolve to eventually form exotic dark stars. We discuss the dynamical complexity of these dark compact objects in light of dark big bang nucleosynthesis. We argue how IQCD favors a halo composed of very compact dark neutron stars, strange/quark stars and black holes, with masses $M_{MACHO}<10^{-7}{M}_{\odot }$. This avoids limit from MACHO and EROS collaborations as well as limit from clusters. We also discuss possible phenomenological implications in dark matter searches. We argue that dark supernovae and dark binaries can emit very peculiar gravitational waves signal testable by the LIGO/VIRGO collaboration and future projects dedicated to these aspects.

    ↳ gr-qcastro-ph.COhep-ph20 citations
29. 29*

    Study of compound nucleus formation via bremsstrahlung emission in proton $\alpha$-particle scattering

    Sergei P. Maydanyuk (1 and 2)🇺🇦 · Peng-Ming Zhang (1 and 3) ((1) Institute of Modern Physics, Chinese Academy of Sciences, (2) Institute for Nuclear Research, National Academy of Sciences of Ukraine, (3) State Key Laboratory of Theoretical Physics, Institute of Theoretical Physics, Chinese Academy of Sciences)🇨🇳

    In this paper a role of many-nucleon dynamics in formation of the compound ${}^5\mathrm{Li}$ nucleus in the scattering of protons off $\alpha$-particles at the proton incident energies up to 20 MeV is investigated. We propose a bremsstrahlung model allowing to extract information about probabilities of formation of such nucleus on the basis of analysis of experimental cross-sections of the bremsstrahlung photons. In order to realize this approach, the model includes elements of microscopic theory and also probabilities of formation of the short-lived compound nucleus. Results of calculations of the bremsstrahlung spectra are in good agreement with the experimental cross-sections.

    ↳ nucl-thhep-phnucl-ex0 citations
30. 30*

    Upper bound on the mass anomalous dimension in many-flavor gauge theories: a conformal bootstrap approach

    Hisashi Iha🇯🇵 · Hiroki Makino🇯🇵 · Hiroshi Suzuki🇯🇵

    We study four-dimensional conformal field theories with an $SU(N)$ global symmetry by employing the numerical conformal bootstrap. We consider the crossing relation associated with a four-point function of a spin~$0$ operator~${\varphi }_i^{\text{Bar}k}$ which belongs to the adjoint representation of $SU(N)$. For~$N=12$ for example, we found that the theory contains a spin~$0$ $SU(12)$-breaking relevant operator when the scaling dimension of~${\varphi }_i^{\text{Bar}k}$, ${\Delta }_{{\varphi }_i^{\text{Bar}k}}$, is smaller than~$1.71$. Considering the lattice simulation of many-flavor quantum chromodynamics with $12$~flavors on the basis of the staggered fermion, the above $SU(12)$-breaking relevant operator, if it exists, would be induced by the flavor-breaking effect of the staggered fermion and prevent an approach to an infrared fixed point. Actual lattice simulations do not show such signs. Thus, assuming the absence of the above $SU(12)$-breaking relevant operator, we have an upper bound on the mass anomalous dimension at the fixed point~${\gamma }_m^{\ast }\le 1.29$ from the relation~${\gamma }_m^{\ast }=3-{\Delta }_{{\varphi }_i^{\text{Bar}k}}$. Our upper bound is not so strong practically but it is strict within the numerical accuracy. We also find a kink-like behavior in the boundary curve for the scaling dimension of another $SU(12)$-breaking operator.

    ↳ hep-thhep-lathep-phPTEP(2016)·28 citations
31. 31*

    Constraining the Schwarzschild-de Sitter Solution in Models of Modified Gravity

    Lorenzo Iorio🇮🇹 · Matteo Luca Ruggiero🇮🇹 · Ninfa Radicella🇮🇹 · Emmanuel N. Saridakis🇺🇸

    The Schwarzschild-de Sitter (SdS) solution exists in the large majority of modified gravity theories, as expected, and in particular the effective cosmological constant is determined by the specific parameters of the given theory. We explore the possibility to use future extended radio-tracking data from the currently ongoing New Horizons mission in the outskirts peripheries of the Solar System, at about 40 au, in order to constrain this effective cosmological constant, and thus to impose constrain on each scenario's parameters. We investigate some of the recently most studied modified gravities, namely $f(R)$ and $f(T)$ theories, dRGT massive gravity, and Hořava-Lifshitz gravity, and we show that New Horizons mission may bring an improvement of one-two orders of magnitude with respect to the present bounds from planetary orbital dynamics.

    ↳ gr-qcastro-ph.EPhep-phphysics.space-phPhys.Dark Univ.(2016)·33 citations
32. 32*

    Fluctuations in Charged Particle Multiplicities in Relativistic Heavy-Ion Collisions

    Maitreyee Mukherjee🇮🇳 · Sumit Basu🇮🇳 · Subikash Choudhury🇮🇳 · Tapan K. Nayak🇮🇳

    Multiplicity distributions of charged particles and their event-by-event fluctuations have been compiled for relativistic heavy-ion collisions from the available experimental data at Brookhaven National Laboratory and CERN and also by the use of an event generator. Multiplicity fluctuations are sensitive to QCD phase transition and to the presence of critical point in the QCD phase diagram. In addition, multiplicity fluctuations provide baselines for other event-by-event measurements. Multiplicity fluctuation expressed in terms of the scaled variance of the multiplicity distribution is an intensive quantity, but is sensitive to the volume fluctuation of the system. The importance of the choice of narrow centrality bins and the corrections of centrality bin width effect for controlling volume fluctuations have been discussed. It is observed that the mean and width of the multiplicity distributions monotonically increase as a function of increasing centrality at all collision energies, whereas the multiplicity fluctuations show minimal variations with centrality. The beam energy dependence shows that the multiplicity fluctuations have a slow rise at lower collision energies and remain constant at higher energies.

    ↳ nucl-exhep-exhep-phnucl-thJ.Phys.G(2016)·17 citations
33. 33*

    A simple alternative to the Crystal Ball function

    Souvik Das🇺🇸

    We present a simple alternative to the Crystal Ball function that has an exponential tail stitched to a Gaussian core. It has one parameter less than the Crystal Ball function and, where appropriate, offers more stable fits to peaks that continue into exponential tails. The function may also be extended with two exponential tails on each side of the Gaussian, and this has two parameters less than the corresponding double-shouldered Crystal Ball function. This function has been used to model background and signal processes in a recent Higgs pair production search and may be of versatile use in experimental physics and other fields.

    ↳ hep-exhep-ph53 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.