Thu·Jan 12, 2017Thursday·January 12, 2017

1. 01*

   Circular polarisation: a new probe of dark matter and neutrinos in the sky

   Celine Boehm🇬🇧 · Celine Degrande🇨🇭 · Olivier Mattelaer🇧🇪 · Aaron C. Vincent🇬🇧

   The study of anomalous electromagnetic emission in the sky is the basis of indirect searches for dark matter. It is also a powerful tool to constrain the radiative decay of active neutrinos. Until now, quantitative analyses have focused on the flux and energy spectrum of such an emission; polarisation has never been considered. Here we show that we could be missing out on an essential piece of information. The radiative decay of neutrinos, as well as the interactions of dark matter and neutrinos with Standard Model particles can generate a circular polarisation signal in X-rays or \gamma-rays. If observed, this could reveal important information about their spatial distribution and particle-antiparticle ratio, and could even reveal the nature of the high-energy particle physics processes taking place in astrophysical sites. The question of the observability of these polarised signatures and their separation from background astrophysical sources is left for future work.

   hep-phastro-ph.HEJCAP(2017)·31 citations
2. 02*

   Charged scalars from $\mathrm{SU}(3{)}^3$ theories

   José Eliel Camargo-Molina🇸🇪 · Roman Pasechnik🇸🇪 · Jonas Wessén🇸🇪

   Inspired by a recently proposed GUT model based on the trinification ($\mathrm{SU}(3{)}^3$) gauge group with a global family ($\mathrm{SU}(3{)}_F$) symmetry, we consider an effective low-energy three Higgs doublet model that may shed light on what underlies the observed fermion mass hierarchies and CKM mixing. We discuss possibilities for charged scalars coming from this model to show in collider experiments and show some interesting benchmark points.

   hep-phPoS(2017)·1 citation
3. 03*

   Pair production processes and flavor in gauge-invariant perturbation theory

   Larissa Egger🇦🇹 · Axel Maas🇦🇹 · René Sondenheimer🇩🇪

   Gauge-invariant perturbation theory is an extension of ordinary perturbation theory which describes strictly gauge-invariant states in theories with a Brout-Englert-Higgs effect. Such gauge-invariant states are composite operators which have necessarily only global quantum numbers. As a consequence, flavor is exchanged for custodial quantum numbers in the standard model, recreating the fermion spectrum in the process. Here, we study the implications of such a description, possibly also for the generation structure of the standard model. In particular, this implies that scattering processes are essentially bound-state-bound-state interactions, and require a suitable description. We analyze the implications for the pair-production process $e^{+}{e}^{-}\to \bar{f}f$ at a linear collider to leading order. We show how ordinary perturbation theory is recovered as the leading contribution. Developing a suitable PDF-type language, we also assess the impact of sub-leading contributions. We find that only for very heavy fermions in the final state, especially top quarks, sizable corrections could emerge. This gives an interesting, possibly experimentally testable, scenario for the formal field theory underlying the electroweak sector of the standard model.

   hep-phhep-exMod.Phys.Lett.A(2017)·30 citations
4. 04*

   Second Order QED Processes in an Intense Electromagnetic Field

   A. Hartin🇬🇧

   Some non linear, second order QED processes in the presence of intense plane electromagnetic waves are investigated. Analytic expressions with general kinematics are derived for Compton scattering and $e^{+}{e}^{-}$ pair production in a circularly polarised external electromagnetic field. The differential cross sections were investigated numerically for photon energies up to 50 MeV, external field intensity parameter ${\nu }^2$ to value 2, and all scattering angles. The variation of full cross sections with respect to external field intensity was also established. The presence of the external field led to resonances in the Compton scattering and pair production differential cross sections. These resonances were investigated by calculating the electron self energy in the presence of the external field. At resonance the differential cross sections were enhanced by several orders of magnitude. The resonances occurred for values of external field intensity parameter ${\nu }^2<1$, lowering the limit of ${\nu }^2\sim 1$ at which point non linear effects in first order external field QED processes become important. Generally, full cross sections increased with increasing external field intensity, though peaking sharply for Compton scattering and levelling off for pair production. An application was made to non linear background studies at $e^{+}{e}^{-}$ linear colliders. The pair production process and electron self energy were studied for the case of a constant crossed electromagnetic field. It was found that previous analytic expressions required the external field to be azimuthally symmetric. New analytic expressions for the more general non azimuthally symmetric case were developed and a numerical parameter range equivalent to that proposed for future linear collider designs was considered.

   hep-phBritish Library, EThOS uk.bl.ethos.436336…·7 citations
5. 05*

   Different Non-extensive Models for heavy-ion collisions

   Keming Shen🇨🇳 · Tamas S. Biro🇭🇺 · Enke Wang🇨🇳

   The transverse momentum ($p_T$) spectra from heavy-ion collisions at intermediate momenta are described by non-extensive statistical models. Assuming a fixed relative variance of the temperature fluctuating event by event or alternatively a fixed mean multiplicity in a negative binomial distribution (NBD), two different linear relations emerge between the temperature, $T$, and the Tsallis parameter $q-1$. Our results qualitatively agree with that of G.~Wilk. Furthermore we revisit the "Soft+Hard" model, proposed recently by G.~G.~Barnaföldi \textit{et.al.}, by a $T$-independent average $p_T^2$ assumption. Finally we compare results with those predicted by another deformed distribution, using Kaniadakis' $\kappa$ parametrization.

   hep-phphysics.data-anPhysica A(2018)·24 citations
6. 06*

   Probing new physics in ${\bar{B}}^0\to D^{(\ast )}{\tau }^{-}{\bar{\nu }}_{\tau }$ using the longitudinal, transverse, and normal polarization components of the tau lepton

   Mikhail A. Ivanov🇷🇺 · Jürgen G. Körner🇩🇪 · Chien-Thang Tran🇷🇺

   We study the longitudinal, transverse, and normal polarization components of the tau lepton in the decays ${\bar{B}}^0\to D^{(\ast )}{\tau }^{-}{\bar{\nu }}_{\tau }$ and discuss their role in searching for new physics (NP) beyond the standard model (SM). Starting with a model-independent effective Hamiltonian including non-SM four-Fermi operators, we obtain experimental constraints on different NP scenarios and investigate their effects on the polarization observables. In the SM the longitudinal and transverse polarizations of the tau lepton differ substantially from the corresponding zero lepton mass values of $P_L=-1$ and $P_T=0$. In addition, $P_L$ and $P_T$ are very sensitive to NP effects. For the transverse polarization this holds true, in particular, for the effective tensor operator in the case of ${\bar{B}}^0\to D^{\ast }$ and for the scalar operator in the case of ${\bar{B}}^0\to D$. The $T$-odd normal polarization $P_N$, which is predicted to be negligibly small in the SM, can be very sizable assuming NP complex Wilson coefficients. We also discuss in some detail how the three polarization components of the tau lepton can be measured with the help of its subsequent leptonic and semihadronic decays.

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

   The S-wave resonance contributions in the $B_s^0$ decays into $\psi (2S,3S)$ plus pion pair

   Zhou Rui🇨🇳 · Ya Li🇨🇳 · Wen-Fei Wang🇨🇳

   The three-body decays $B_s^0\to \psi (2S,3S){\pi }^{+}{\pi }^{-}$ are studied based on the perturbative QCD approach. With the help of the nonperturbative two-pion distribution amplitudes, the analysis is simplified into the quasi-two-body processes. Besides the traditional factorizable and nonfactorizable diagrams at the leading order, the next-to-leading order vertex corrections are also included to cancel the scale dependence. The $f_0(980)$, $f_0(1500)$ resonance contributions as well as the nonresonant contributions are taken into account using the presently known $\pi \pi$ time-like scalar form factor for the $s\bar{s}$ component. It is found that the predicted $B_s^0\to \psi (2S){\pi }^{+}{\pi }^{-}$ decay spectra in the pion pair invariant mass shows a similar behavior as the experiment. The calculated S-wave contributions to the branching ratio of $B_s^0\to \psi (2S){\pi }^{+}{\pi }^{-}$ is $6.0\times 10^{-5}$, which is in agreement with the LHCb data $\mathcal{B}(B_s^0\to \psi (2S){\pi }^{+}{\pi }^{-})=(7.2\pm 1.2)\times 10^{-5}$ within errors. The estimate of $\mathcal{B}(B_s^0\to \psi (3S){\pi }^{+}{\pi }^{-})$ can reach the order of $10^{-5}$, pending for the corresponding measurements.

   hep-phEPJC(2017)·39 citations
8. 08*

   Some properties of the states at the hidden-strangeness mixed ${\frac{1}{2}}^{+}+{\frac{1}{2}}^{-}$ heavy meson pair threshold in $e^{+}{e}^{-}$ annihilation

   M.B. Voloshin🇺🇸

   The threshold behavior of $e^{+}{e}^{-}$ annihilation is considered in the channels $B_{s0}{\bar{B}}_s^{\ast }+c.c.$, $B_{s1}{\bar{B}}_s+c.c.$, and $B_{s1}{\bar{B}}_s^{\ast }+c.c.$, where $B_{s0}$ and $B_{s1}$ are the excited bottom-strange $J^P=0^{+}$ and $J^P=1^{+}$ mesons. It is argued that due to the heavy quark spin symmetry (HQSS) only one coherent combination of the first two channels is produced in the $S$ wave as well as the third channel. Thus, if there exist threshold molecular peaks in the considered channels, only two of such peaks can be formed in the annihilation. The properties of such threshold states are discussed, including the heavy-light spin structure and the related transitions to bottomonium plus light mesons, as well as mixing with the channels with and without hidden strangeness.

   hep-phPRD(2017)·4 citations
9. 09*

   Gravitino Problem in Minimal Supergravity Inflation

   Fuminori Hasegawa🇯🇵 · Kyohei Mukaida🇯🇵 · Kazunori Nakayama🇯🇵 · Takahiro Terada🇰🇷 · Yusuke Yamada🇺🇸

   We study non-thermal gravitino production in the minimal supergravity inflation. In this minimal model utilizing orthogonal nilpotent superfields, the particle spectrum includes only graviton, gravitino, inflaton, and goldstino. We find that a substantial fraction of the cosmic energy density can be transferred to the longitudinal gravitino due to non-trivial change of its sound speed. This implies either a breakdown of the effective theory during reheating or a serious gravitino problem.

   hep-phastro-ph.COhep-thPLB(2017)·41 citations
10. 10*

    The Z boson spin observables as messengers of new physics

    J.A. Aguilar-Saavedra🇪🇸 · J. Bernabéu🇪🇸 · V.A. Mitsou🇪🇸 · A. Segarra🇪🇸

    We demonstrate that the 8 multipole parameters describing the spin state of the $Z$ boson are able to disentangle known $Z$ production mechanisms and signals from new physics at the LHC. They can be extracted from appropriate asymmetries in the angular distribution of lepton pairs from the $Z$ boson decay. The power of this analysis is illustrated by (i) the production of $Z$ boson plus jets; (ii) $Z$ boson plus missing transverse energy; (iii) $W$ and $Z$ bosons originating from the two-body decay of a heavy resonance.

    hep-phhep-exEPJC(2017)·43 citations
11. 11*

    Lattice Generalized Parton Distributions and Form Factors of the Nucleon

    Martha Constantinou🇺🇸

    In these proceedings we discuss recent progress in nucleon structure using lattice QCD simulations at or near the physical value of the pion mass. Main focus will be given in observables such as the nucleon axial charge and the first moments of parton distributions, for both the valence and sea quark contributions, and discuss their implications on the spin content of the nucleon. We will will also report developments on the evaluation of the gluon momentum fraction, which contributes significantly to the nucleon spin.

    ↳ hep-lathep-phnucl-th2 citations
12. 12*

    Exploratory Lattice QCD Study of the Rare Kaon Decay $K^{+}\to {\pi }^{+}\nu \bar{\nu }$

    Ziyuan Bai🇺🇸 · Norman H. Christ🇺🇸 · Xu Feng🇺🇸 · Andrew Lawson🇬🇧 · Antonin Portelli🇬🇧 · Christopher T. Sachrajda🇬🇧

    We report a first, complete lattice QCD calculation of the long-distance contribution to the $K^{+}\to {\pi }^{+}\nu \bar{\nu }$ decay within the standard model. This is a second-order weak process involving two four-Fermi operators that is highly sensitive to new physics and being studied by the NA62 experiment at CERN. While much of this decay comes from perturbative, short-distance physics there is a long-distance part, perhaps as large as the planned experimental error, which involves nonperturbative phenomena. The calculation presented here, with unphysical quark masses, demonstrates that this contribution can be computed using lattice methods by overcoming three technical difficulties: (i) a short-distance divergence that results when the two weak operators approach each other, (ii) exponentially growing, unphysical terms that appear in Euclidean, second-order perturbation theory, and (iii) potentially large finite-volume effects. A follow-on calculation with physical quark masses and controlled systematic errors will be possible with the next generation of computers.

    ↳ hep-lathep-exhep-phPRL(2017)·39 citations
13. 13*

    Search for Dark Matter with top quarks

    Jeremy Andrea🇫🇷

    This proceeding presents searches for Dark Matter particles produced in association with top quarks at the LHC. The searches are performed by the ATLAS and CMS collaborations and various models and topologies are investigated. They are exploiting tt and single top experimental signatures by searching for an excess of missing transverse energy. No signs of Dark Matter particles haven been observed and limits on the models are set.

    ↳ hep-exhep-ph2 citations
14. 14*

    The $\Lambda$-parameter in 3-flavour QCD and ${\alpha }_s(m_Z)$ by the ALPHA collaboration

    M. Bruno🇺🇸 · M. Dalla Brida🇩🇪 · P. Fritzsch🇨🇭 · T. Korzec🇩🇪 · A. Ramos🇨🇭 · S. Schaefer🇩🇪 · H. Simma🇩🇪 · S. Sint🇮🇪 · R. Sommer🇩🇪

    We present results by the ALPHA collaboration for the $\Lambda$-parameter in 3-flavour QCD and the strong coupling constant at the electroweak scale, ${\alpha }_s(m_Z)$, in terms of hadronic quantities computed on the CLS gauge configurations. The first part of this proceedings contribution contains a review of published material \cite{Brida:2016flw,DallaBrida:2016kgh} and yields the $\Lambda$-parameter in units of a low energy scale, $1/L_{\mathrm{had}}$. We then discuss how to determine this scale in physical units from experimental data for the pion and kaon decay constants. We obtain ${\Lambda }_{\overline{\mathrm{MS}}}^{(3)}=332(14)$ MeV which translates to ${\alpha }_s(M_Z)=0.1179(10)(2)$ using perturbation theory to match between 3-, 4- and 5-flavour QCD.

    ↳ hep-lathep-phPoS(2016)·13 citations
15. 15*

    FRB 121102 Casts New Light on the Photon Mass

    Luca Bonetti🇫🇷 · John Ellis🇬🇧 · Nikolaos E. Mavromatos🇬🇧 · Alexander S. Sakharov🇨🇭 · Edward K. Sarkisyan-Grinbaum🇨🇭 · Alessandro D.A.M. Spallicci🇫🇷

    The photon mass, $m_{\gamma }$, can in principle be constrained using measurements of the dispersion measures (DMs) of fast radio bursts (FRBs), once the FRB redshifts are known. The DM of the repeating FRB 121102 is known to $<1$\%, a host galaxy has now been identified with high confidence,and its redshift, $z$, has now been determined with high accuracy: $z=0.19273(8)$. Taking into account the plasma contributions to the DM from the Intergalactic medium (IGM) and the Milky Way, we use the data on FRB 121102 to derive the constraint $m_{\gamma }\lesssim 2.2\times 10^{-14}$ eV c${}^{-2}$ ($3.9\times 10^{-50}$ kg). Since the plasma and photon mass contributions to DMs have different redshift dependences, they could in principle be distinguished by measurements of more FRB redshifts, enabling the sensitivity to $m_{\gamma }$ to be improved.

    ↳ astro-ph.HEastro-ph.COhep-exhep-phPLB(2017)·61 citations
16. 16*

    Dilepton and $\varphi$ meson production in elementary and nuclear collisions at the NICA fixed target experiment

    Gy. Wolf \🇭🇺 · M. Zétényi🇭🇺

    We argue that the NICA fixed target experiment will be able to provide very important new experimental data on dilepton and $\varphi$ meson production in the basically undiscovered energy domain between the SIS and SPS energies. Experimental information about elementary cross sections in this energy region is an essential ingredient of models of nuclear collisions in the same energy range.

    ↳ nucl-thhep-exhep-phnucl-exEPJA(2016)·0 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.