Tue·Oct 24, 2017Tuesday·October 24, 2017

1. 01*

   Light Signals from a Lighter Higgs

   Patrick J. Fox🇺🇸 · Neal Weiner🇺🇸

   With the Higgs search program already quite mature, there is the exciting possibility of discovering a new particle with rates near that of the SM Higgs. We consider models with a signal in $\gamma \gamma$ below the SM Higgs mass, taking the recent $2.9\sigma$ (local) CMS excess at 95 GeV as a target. We discuss singlet models with additional vectorlike matter, but argue that a Type-I two Higgs doublet model provides a more economical scenario. In such a setup, going into regions of moderate-to-strong fermiophobia, the enhanced $\gamma \gamma$ branching ratio allows signals from $VH$+VBF production to yield $\sigma \times B{R}_{\gamma \gamma }$ comparable to total SM rates. Light $H$ production can be dominated via rare top decays $t\to b{H}^{+}\to b{W}^{\ast }H$, which provides an alternate explanation of the excess. We consider this in the context of other Higgs anomalies, namely the LEP Higgs excess near the same mass, and excesses in $t\bar{t}h$ searches at Tevatron and LHC. We find that with $140\mathrm{GeV}<m_{H^{+}}<160\mathrm{GeV}$, $\tan \beta \sim 5$ and a coupling to gauge bosons of ${\sin }^2\delta \sim 0.1$, such a scenario can produce all the excesses simultanously, where $tth$ arise from contamination from the rare top decays, as previously proposed. An implication of the Type-I scenario is that any $\gamma \gamma$ excess should be associated with additional elements that could reduce background, including $b$-jets, forward jets or signs of vector boson production.

   hep-phJHEP(2018)·71 citations
2. 02*

   Direct photon spectrum and elliptic flow produced from Pb+Pb collisions at $\sqrt{s_{NN}}=2.76$ TeV at the CERN Large Hadron Collider within an integrated hydrokinetic model

   V.Yu. Naboka🇺🇦 · Yu.M. Sinyukov🇺🇦 · G.M. Zinovjev🇺🇦

   The photon transverse momentum spectrum and its anisotropy from Pb+Pb collisions at the CERN Large Hadron Collider energy $\sqrt{s_{NN}}=2.76$ TeV are investigated within the integrated hydrokinetic model (iHKM). Photon production is accumulated from the different processes at the various stages of relativistic heavy ion collisions: from the primary hard photons of very early stage of parton collisions to the thermal photons from equilibrated quark-gluon and hadron gas stages. Along the way a hadronic medium evolution is treated in two distinct, in a sense opposite, approaches: chemically equilibrated and chemically frozen system expansion. Studying the centrality dependence of the results obtained allows us to conclude that a relatively strong transverse momentum anisotropy of thermal radiation is suppressed by prompt photon emission which is an isotropic. We find out that this effect is getting stronger as centrality increases because of the simultaneous increase in the relative contribution of prompt photons in the soft part of the spectra. The substantial results obtained in iHKM with nonzero viscosity ($\eta /s=0.08$) for photon spectra and $v_2$ coefficients are mostly within the error bars of experimental data, but there is some systematic underestimation of both observables for the near central events. We claim that a situation could be significantly improved if an additional photon radiation that accompanies the presence of a deconfined environment is included. Since a matter of a space-time layer where hadronization takes place is actively involved in anisotropic transverse flow, both positive contributions to the spectra and $v_2$ are considerable, albeit such an argument needs further research and elaboration.

   hep-phnucl-exnucl-thPRC(2018)·11 citations
3. 03*

   Effect of PYTHIA8 tunes on event shapes and top-quark reconstruction in $e^{+}{e}^{-}$ annihilation at CLIC

   S. Chekanov🇺🇸 · M. Demarteau🇺🇸 · A. Fischer🇺🇸 · J. Zhang🇺🇸

   This paper describes the effect of PYTHIA8 tunes on event simulation of $e^{+}{e}^{-}$ collisions with center-of-mass (CM) energies of 380 GeV and 3 TeV at the proposed CLIC collider. Event shapes, such as thrust, thrust major, thrust minor, oblateness, as well as particle multiplicities have been analyzed and relative differences with respect to the default PYTHIA8 tune were determined. The effect of tunes on top-mass reconstruction in the resolved and boosted regimes was analyzed. No statistically significant variation for reconstructed top masses using invariant masses of three jets was found for events with a CM energy of 380 GeV. For the fully boosted top reconstruction at a CM energy of 3 TeV, a significant shift in reconstructed top mass of about 700 MeV for the "Montull" tune was observed. This shift correlates with an increase in particle multiplicity compared to all other PYTHIA8 tunes.

   hep-ph6 citations
4. 04*

   The Axion and the Goldstone Higgs

   I. Brivio🇩🇰 · M.B. Gavela🇪🇸 · S. Pascoli🇬🇧 · R. del Rey🇪🇸 · S. Saa🇪🇸

   We consider the renormalizable $SO(5)/SO(4)$ $\sigma$-model, in which the Higgs particle has a pseudo-Nambu-Goldstone boson character, and explore what the minimal field extension required to implement the Peccei-Quinn symmetry (PQ) is, within the partial compositeness scenario. It turns out that the minimal model does not require the enlargement of the exotic fermionic sector, but only the addition of a singlet scalar: it is sufficient that the exotic fermions involved in partial compositeness and the singlet scalar become charged under Peccei-Quinn transformations. We explore the phenomenological predictions for photonic signals in axion searches for all models discussed. Because of the constraints imposed on the exotic fermion sector by the Standard Model fermion masses, the expected range of allowed axion-photon couplings turns out to be generically narrowed with respect to that of standard invisible axion models, impacting the experimental quest.

   hep-phChin.J.Phys.(2019)·22 citations
5. 05*

   Bread and butter physics: NLO electroweak corrections to polarized top quark decays

   S. Groote🇪🇪 · J.G. Körner🇩🇪

   We report on the status of an ongoing calculation of the NLO electroweak corrections to sequential polarized top quark decays $t(\uparrow )\to X_b+W^{+}(\to {\ell }^{+}+{\nu }_{\ell })$.

   hep-phhep-exJ.Phys.Conf.Ser.(2017)·1 citation
6. 06*

   Status Update on Selective SUSY GUT Inspired Models

   Muhammad Adeel Ajaib🇶🇦 · Ilia Gogoladze🇺🇸

   We perform a status analysis of selective supersymmetric GUT models in light of recent constraints from collider and dark matter detection experiments. We find that a significant region of the parameter space of these models is still accessible to these experiments. Amongst the models we analyze, the split family model provides solutions that can explain the observed deviation in anomalous magnetic moment of the muon. Furthermore, there is a notable region of the parameter space of each model which yields the desired relic abundance for neutralino dark matter. We also present the prediction of spin independent and spin dependent neutralino cross sections in these models and find that there is parameter space which can be probed at future experiments searching for dark matter. Our analysis serves as a motivation to continue the search for supersymmetry at various experimental fronts.

   hep-ph7 citations
7. 07*

   A new U(1) model anomaly free for three families to address fermion mass hierarchy and neutrino physics

   S. F. Mantilla🇨🇴 · R. Martinez🇨🇴

   A new non-universal abelian extension ${\mathrm{G}}_{\mathrm{SM}}\otimes {\mathrm{U}(1)}_X$ to the Standard Model free from chiral anomalies is presented. The new $X$ charges distinguish among generations so as the fermion mass matrices get zero-textures from the fermion mass hierarchy can be obtained. Regarding to neutrino physics, the model inclues Majorana fermions which induce see-saw mechanisms to get small neutrino masses. Moreover, the suitability of the model is tested by searching for regions in the parameter space which reproduce current neutrino oscillation data.

   hep-phhep-th1 citation
8. 08*

   NNLO QCD Corrections to $\gamma +{\eta }_c({\eta }_b)$ Exclusive Production in Electron-Positron Collision

   Long-Bin Chen🇨🇳 · Yi Liang🇨🇳 · Cong-Feng Qiao🇨🇳

   Based on the NRQCD factorization formalism, we calculate the next-to-next-to-leading order QCD corrections to the heavy quarkonium ${\eta }_c({\eta }_b)$ production associated with a photon at electron-positron colliders. By matching the amplitudes calculated in full QCD theory to a series of operators in NRQCD, the short-distance coefficients up to NNLO QCD radiative corrections are determined. It turns out that the full set of master integrals that we obtained could be analytically expressed in terms of Goncharov Polylogarithms, Chen's iterated integrals, and elliptic functions, which mostly do not exist in the literature and could be employed in the analyses of other physical processes. In phenomenology, numerical calculations of NNLO K-factors and cross sections of $e^{+}{e}^{-}\to \gamma +{\eta }_c({\eta }_b)$ processes in BESIII and B-factory experiments are performed, which may stand as a test of the NRQCD higher order calculation while confronting to the data.

   hep-phJHEP(2018)·35 citations
9. 09*

   The role of theory input for exclusive $V_{cb}$ determinations

   Stefan Schacht🇮🇹

   Available form factor parametrizations for $B\to D^{\ast }l\nu$ imply different theoretical assumptions and different treatments of theoretical uncertainties. They give results for $|V_{cb}|$ whose central values are apart by up to $8\%$. The way the Caprini Lellouch Neubert (CLN) parametrization has been used in experimental analyses sets theoretical uncertainties of the Heavy Quark Effective Theory (HQET) results on slope and curvature of the form factor ratios $R_1$ and $R_2$ to zero. Furthermore, the relation of curvature and slope of the axial form factor $A_1$ is fixed to the HQET central value. In view of the current experimental precision these uncertainties cannot be neglected any more. Using the Boyd Grinstein Lebed (BGL) parametrization and taking into account theoretical uncertainties in a conservative way, we extract $|V_{cb}|$ from recent preliminary Belle data and the world average of the total branching ratio. We include an $\mathcal{O}(10\%-20\%)$ theoretical uncertainty of HQET input due to unknown corrections beyond NLO which were neglected in all previous analyses. This is important for reliable extractions of $|V_{cb}|$ as well as precision tests of the Standard Model with robust predictions of the lepton flavor nonuniversality observable $R(D^{\ast })$ and the $\tau$ polarization asymmetry $P_{\tau }$. Including input from Light Cone Sum Rules (LCSRs) we find $|V_{cb}|=40.6\left({}_{-1.3}^{+1.2}\right)\cdot 10^{-3}$, $R(D^{\ast })=0.260(8)$ and $P_{\tau }=-0.47(4)$. Without LCSRs we find $|V_{cb}|=41.5(1.3)\cdot 10^{-3}$ and the same results for $R(D^{\ast })$ and $P_{\tau }$. The $R(D^{\ast })$ anomaly is persistent, but its statistical significance is slightly reduced to 2.6$\sigma$.

   hep-phPoS(2017)·2 citations
10. 10*

    Lepton flavor violation from low scale seesaw neutrinos with masses reachable at the LHC

    X. Marcano🇪🇸

    Flavor physics has been crucial in the development of particle physics and it will keep being so in the future. Nowadays, this kind of processes, in particular lepton flavor changing observed in neutrino oscillations, give us the clearest evidence of the fact that the Standard Model of fundamental interactions needs to be modified. Some of the most popular theories that try to asses this issue postulate the existence of new heavy right-handed neutrinos, with masses in the energy range that the LHC experiment is currently exploring. In this thesis, we study the connection between the possible existence of these neutrinos and charged lepton flavor changing physics. We consider the inverse seesaw model as a particular realization of a low scale seesaw model and analyze its lepton flavor violating phenomenology, in particular the Higgs and Z boson decays to two charged leptons of different flavor. Moreover, we also explore the possibility of having new exotic lepton flavor violating signals at the LHC, coming from the production and decay of these new heavy neutrinos.

    hep-ph13 citations
11. 11*

    Triple top signal as a probe of charged Higgs in a 2HDM

    Riley Patrick🇦🇺 · Pankaj Sharma🇦🇺 · Anthony G. Williams🇦🇺

    Within the framework of the type-II Two Higgs Doublet Model (2HDM-II) we study the production of three top quarks at the Large Hadron Collider (LHC). In the Standard Model the production cross section of three tops is low ($\approx 3$fb), while it is expected to be significant in the 2HDM-II for reasonable choices of the parameters. We study the production of a charged Higgs in association with a top quark, followed by the decays $H^{\pm }\to W^{\pm }A$ and $A\to t\bar{t}$. We undertake a full detector simulation of the signal, and use simple conservative cuts, focusing on the final states that contain three or more leptons, and exactly one same sign di-lepton pair. Finally, we present the exclusion bounds dependent on charged Higgs and pseudoscalar Higgs masses expected in the near future at the 14TeV LHC.

    hep-phPLB(2018)·7 citations
12. 12*

    Probing Higgs self-coupling of a classically scale invariant model in $e^{+}{e}^{-}\to Zhh$: Evaluation at physical point

    Yoshio Fujitani🇯🇵 · Yukinari Sumino🇯🇵

    A classically scale invariant extension of the standard model predicts large anomalous Higgs self-interactions. We compute missing contributions in previous studies for probing the Higgs triple coupling of a minimal model using the process $e^{+}{e}^{-}\to Zhh$. Employing a proper order counting, we compute the total and differential cross sections at the leading order, which incorporate the one-loop corrections between zero external momenta and their physical values. Discovery/exclusion potential of a future $e^{+}{e}^{-}$ collider for this model is estimated. We also find a unique feature in the momentum dependence of the Higgs triple vertex for this class of models.

    hep-phPLB(2018)·2 citations
13. 13*

    Direct, Resonant Production of States with Positive Charge Conjugation in Electron-Positron Annihilation

    Henryk Czyż🇵🇱 · Johann H. Kühn🇩🇪 · Szymon Tracz🇵🇱

    Recent theory results on direct production of resonances with positive charge conjugation in electron-positron annihilation are reviewed. The strong model dependence is emphasized, with predictions varying between 0.03 eV and 0.43 eV for the charmonium state with $J^{PC}=1^{++}$ and between 0.16 eV and 4.25 eV for the state with $J^{PC}=2^{++}$. For the state with $J^{PC}=0^{++}$ the cross section is of $\mathcal{O}$ $(m_e^2/M_{\chi }^2)$ and thus negligeable for all practical purpose. The importance of the relative phase of the production amplitude is emphasized.

    hep-phEPJ Web Conf.(2019)·1 citation
14. 14*

    Electromagnetic decays of the neutral pion investigated in the Dyson-Schwinger formalism

    Esther Weil🇩🇪 · Gernot Eichmann🇵🇹 · Christian S. Fischer🇩🇪 · Richard Williams🇩🇪

    We summarize recent work in determining the transition form factor (TFF) of the neutral pion (${\pi }^0\to {\gamma }^{\ast }{\gamma }^{\ast }$), by solving the non-perturbative Dyson-Schwinger and Bethe-Salpeter equations. We first study the transition form factor, followed by the rare decay ${\pi }^0\to e^{+}{e}^{-}$, which requires the TFF as input. In addition to the aspects of truncation required to compute the solution, we discuss unexpected behavior in the large $Q^2$ regime (with $Q^2$ the photon virtuality), and also touch on a path deformation in the complex plane to access the total decay rate for the rare decay.

    hep-phJ.Phys.Conf.Ser.(2018)·6 citations
15. 15*

    Muon bundles from the Universe

    P. Kankiewicz🇵🇱 · M. Rybczynski🇵🇱 · Z. Wlodarczyk🇵🇱 · G. Wilk🇵🇱

    Recently the CERN ALICE experiment, in its dedicated cosmic ray run, observed muon bundles of very high multiplicities, thereby confirming similar findings from the LEP era at CERN (in the CosmoLEP project). Significant evidence for anisotropy of arrival directions of the observed high multiplicity muonic bundles is found. Estimated directionality suggests their possible extragalactic provenance. We argue that muonic bundles of highest multiplicity are produced by strangelets, hypothetical stable lumps of strange quark matter infiltrating our Universe.

    hep-phEPJ Web Conf.(2018)·2 citations
16. 16*

    Stable heavy pentaquarks in constituent models

    J.-M. Richard🇫🇷 · A. Valcarce🇪🇸 · J. Vijande🇪🇸

    It is shown that standard constituent quark models produce $(\bar{c}cqqq)$ hidden-charm pentaquarks, where $c$ denotes the charmed quark and $q$ a light quark, which lie below the lowest threshold for spontaneous dissociation and thus are stable in the limit where the internal $\bar{c}c$ annihilation is neglected. The binding is a cooperative effect of the chromoelectric and chromomagnetic components of the interaction, and it disappears in the static limit with a pure chromoelectric potential. Their wave function contains color sextet and color octet configurations for the subsystems and can hardly be reduced to a molecular state made of two interacting hadrons. These pentaquark states could be searched for in the experiments having discovered or confirmed the hidden-charm meson and baryon resonances.

    hep-phPLB(2017)·34 citations
17. 17*

    Magnetic Dipole Transitions of $B_c$ and $B_c^{\ast }$ mesons in the Relativistic Independent Quark Model

    Sonali Patnaik🇮🇳 · P. C. Dash🇮🇳 · S. Kar🇮🇳 · S. Patra🇮🇳 · N. Barik🇮🇳

    We study M1-transitions involving mesons: $B_c(1s)$, $B_c^{\ast }(1s)$, $B_c(2s)$, $B_c^{\ast }(2s)$, $B_c(3s)$ and $B_c^{\ast }(3s)$ in the relativistic independent quark (RIQ) model based on a flavor independent average potential in the scalar-vector harmonic form. The transition form factor for $B_c^{\ast }\to B_c\gamma$ is found to have analytical continuation from spacelike to physical timelike region. Our predicted coupling constant $g_{B_c^{\ast }{B}_c}$ = 0.34 Ge$V^{-1}$ and decay width $\Gamma (B_c^{\ast }\to B_c\gamma )$ = 23 eV agree with other model predictions. In view of possible observation of $B_c$ and $B_c^{\ast }$ s-wave states at LHC and Z-factory and potential use of theoretical estimate on M1-transitions, we investigate the allowed as well as hindered transitions of orbitally excited $B_c$-meson states and predict their decay widths in overall agreement with other model predictions. We consider the typical case of $B_c^{\ast }(1s)\to B_c(1s)\gamma$, where our predicted decay width which is found quite sensitive to the mass difference between $B_c^{\ast }$ and $B_c$ mesons may help in determining the mass of $B_c^{\ast }$ experimentally.

    hep-phPRD(2017)·22 citations
18. 18*

    On the reinterpretation of non-resonant searches for Higgs boson pairs

    Alexandra Carvalho🇪🇪 · Florian Goertz🇩🇪 · Ken Mimasu🇧🇪 · Maxime Gouzevitch🇫🇷 · Anamika Aggarwal🇳🇱

    The detection of production of a pair of Higgs bosons before the end of LHC operation would be clear evidence of New Physics (NP). As searches for non-resonant production of Higgs pairs are being designed it is of particular importance to be able to conveniently present current experimental results in terms of limits in the most 'model-independent' fashion possible. In this article we provide an analytic parametrization of the {\it differential} Higgs-pair production at the LHC in the effective field theory (EFT) extension of the SM. It results from a fit to the theory prediction for the $gg\to hh$ cross section at the 13\,TeV at the LHC. Subsequently the resulting formula is used for a reweighing technique that allows to recast exclusion bounds from ATLAS and CMS HH$\to \gamma \gamma b\bar{b}$ searches to any point of the considered EFT parameter space. We demonstrate with a fast simulation of the LHC detectors that with this approach it is possible to cover the continuously of the EFT parameter space, taking correctly into account the efficiencies of signal selections, without the necessity of rerunning a large number of full detector simulations. Finally, the resulting exclusion bounds are confronted to several explicit models such as setups with additional scalars, including 2HDM, vector-like fermions, and minimal composite Higgs models, mapped to the EFT.

    hep-phJHEP(2021)·30 citations
19. 19*

    Leptonic CP violation in the charged sector and effective field theory approach

    Giovanni Marco Pruna🇨🇭

    These proceedings introduce the main techniques and ideas for a systematic effective field theory analysis of CP violation in the charged lepton sector. This study is required because the Standard Model of particle physics predicts a very high degree of CP violation suppression in the lepton sector, and this implies that possible new physics effects can be parameterised in terms of new interactions among the Standard Model fields, in the framework of the so-called Standard Model Effective Field Theory. In analogy with previous investigations of charged lepton flavour violating observables, this document illustrates how the current limits on leptonic CP violation coming from the electric-dipole moment of the leptons can be recast into constraints on the effective coefficients defined at a given decoupling scale. Furthermore, important bounds acting on previously unconstrained parameters are discussed.

    hep-phPoS(2017)·12 citations
20. 20*

    Tetraquark and two-meson states at large $N_{\mathrm{c}}$

    Wolfgang Lucha🇦🇹 · Dmitri Melikhov🇦🇹 · Hagop Sazdjian🇫🇷

    Considering four-point correlation functions of color-singlet quark bilinears, we investigate, in the large-$N_{\mathrm{c}}$ limit of QCD, the subleading diagrams that involve, in the $s$-channel of meson-meson scattering amplitudes, two-quark--two-antiquark intermediate states. The latter contribute, together with gluon exchanges, to the formation, at the hadronic level, of two-meson and tetraquark intermediate states. It is shown that the two-meson contributions, which are predictable, in general, from leading-order $N_{\mathrm{c}}$-behaviors, consistently satisfy the constraints resulting from the $1/N_{\mathrm{c}}$ expansion procedure and thus provide a firm basis for the extraction of tetraquark properties from $N_{\mathrm{c}}$-subleading diagrams. We find that, in general, tetraquarks, if they exist in compact form, should have narrow decay widths, of the order of $N_{\mathrm{c}}^{-2}$. For the particular case of exotic tetraquarks, involving four different quark flavors, two different types of tetraquark are needed, each having a preferred decay channel, to satisfy the consistency constraints.

    hep-phEPJC(2017)·35 citations
21. 21*

    Masses and decay widths of scalar $D_0$ and $D_{s0}$ mesons in strange hadronic medium

    Rahul Chhabra🇮🇳 · Arvind Kumar🇮🇳

    Masses and decay constants of scalar $D_0$ and $D_{s0}$ mesons in isospin asymmetric strange hadronic matter at finite temperature are evaluated using QCD sum rules and chiral SU(3) model. In-medium light quark condensates, ${⟨\bar{u}u⟩}_{{\rho }_B}$ and ${⟨\bar{d}d⟩}_{{\rho }_B}$, the strange quark condensates, ${⟨\bar{s}s⟩}_{{\rho }_B}$, and the gluon condensates, ${⟨\frac{{\alpha }_s}{\pi }{G^a}_{\mu \nu }{G^a}^{\mu \nu }⟩}_{{\rho }_B}$, needed in QCD sum rule calculations are evaluated using chiral SU(3) model. As an application, we calculate the in-medium partial decay width of scalar $D_0$ ($D_{s0}$) meson decaying to $D$ + $\pi$ ($D_s$+$\pi$) pseudoscalar mesons using ${}^3{P}_0$ model. The medium effects in their decay widths are assimilated through the modification in the masses of these mesons. These results may be helpful to understand the possible outcomes of the future experiments like CBM and PANDA under the FAIR facility where the study of charmed hadrons is one of major goal.

    hep-phnucl-thPRC(2018)·9 citations
22. 22*

    Inhomogeneous phases at finite density in an external magnetic field

    Jens O. Andersen🇳🇴 · Patrick Kneschke🇳🇴

    The two-flavor quark-meson model is used as a low-energy effective model for QCD to study inhomogeneous chiral condensates at finite quark chemical potential $\mu$ in a constant magnetic background $B$. We determine the parameters of the model by matching the meson and quark masses, and the pion decay constant to their physical values using the on-shell and modified minimal subtraction schemes. We calculate the free energy in the mean-field approximation for a chiral density wave using dimensional regularization. The system has a surprisingly rich phase structure.

    hep-ph3 citations
23. 23*

    High Energy Resummation of Jet Observables

    Simone Zoia🇩🇪 · Claudio Muselli🇮🇹

    In this paper we investigate the extension of high energy resummation at LLx accuracy to jet observables. In particular, we present the high energy resummed expression of the transverse momentum distribution of the outgoing parton in the general partonic process $g(q)+g(q)\to g(q)+X$. In order to reach this result, several new ideas are introduced and exploited. First we prove that LLx resummation is achieved by dressing with hard radiation an off-shell gluon initiated LO process even if its on-shell limit is vanishing or trivial. Then we present a gauge-invariant framework where these calculations can be performed by using the modern helicity techniques. Finally, we show a possible way to restore gluon indistinguishability in the final state, which is otherwise lost in the resummation procedure, at all orders in ${\alpha }_s$ at LLx. All partonic channels are then resummed and cross-checked against fixed-order calculations up to $\mathcal{O}({\alpha }_s^3)$

    hep-phJHEP(2017)·5 citations
24. 24*

    Light dark Higgs boson in minimal sub-GeV dark matter scenarios

    Luc Darmé🇵🇱 · Soumya Rao🇵🇱 · Leszek Roszkowski🇵🇱

    Minimal scenarios with light (sub-GeV) dark matter whose relic density is obtained from thermal freeze-out must include new light mediators. In particular, a very well-motivated case is that of a new "dark" massive vector gauge boson mediator. The mass term for such mediator is most naturally obtained by a "dark Higgs mechanism" which leads to the presence of an often long-lived dark Higgs boson whose mass scale is the same as that of the mediator. We study the phenomenology and experimental constraints on two minimal, self-consistent dark sectors that include such a light dark Higgs boson. In one the dark matter is a pseudo-Dirac fermion, in the other a complex scalar. We find that the constraints from BBN and CMB are considerably relaxed in the framework of such minimal dark sectors. We present detection prospects for the dark Higgs boson in existing and projected proton beam-dump experiments. We show that future searches at experiments like Xenon1T or LDMX can probe all the relevant parameter space, complementing the various upcoming indirect constraints from astrophysical observations.

    hep-phhep-exJHEP(2018)·69 citations
25. 25*

    Probing new charged scalars with neutrino trident production

    Gabriel Magill🇨🇦 · Ryan Plestid🇨🇦

    We investigate the possibility of using neutrino trident production to probe leptophilic charged scalars at future high intensity neutrino experiments. We show that under specific assumptions, this production process can provide competitive sensitivity for generic charged scalars as compared to common existing bounds. We also investigate how the recently proposed mixed-flavour production - where the two oppositely charged leptons in the final state need not be muon flavoured - can give a 20-50% increase in sensitivity for certain configurations of new physics couplings as compared to traditional trident modes. We then categorize all renormalizable leptophilic scalar extensions based on their representation under $SU(2)\times U(1)$, and discuss the Higgs triplet and Zee-Babu models as explicit UV realizations. We find that the inclusion of additional doubly charged scalars and the need to reproduce neutrino masses make trident production uncompetitive with current bounds for these specific UV completions. Our work represents the first application of neutrino trident production to study charged scalars, and of mixed-flavour final states to study physics beyond the Standard Model.

    hep-phPRD(2018)·19 citations
26. 26*

    Soft collinear effective theory for gravity

    Takemichi Okui🇺🇸 · Arash Yunesi🇺🇸

    We present how to construct a Soft Collinear Effective Theory (SCET) for gravity at the leading and next-to-leading powers from the ground up. The soft graviton theorem and decoupling of collinear gravitons at the leading power are manifest from the outset in the effective symmetries of the theory. At the next-to-leading power, certain simple structures of amplitudes, which are completely obscure in Feynman diagrams of the full theory, are also revealed, which greatly simplifies calculations. The effective lagrangian is highly constrained by effectively multiple copies of diffeomorphism invariance that are inevitably present in gravity SCET due to mode separation, an essential ingredient of any SCET. Further explorations of effective theories of gravity with mode separation may shed light on lagrangian-level understandings of some of the surprising properties of gravitational scattering amplitudes. A gravity SCET with an appropriate inclusion of Glauber modes may serve as a powerful tool for studying gravitational scattering in the Regge limit.

    ↳ hep-thgr-qchep-phPRD(2018)·18 citations
27. 27*

    Pure spin-3/2 propagator for use in particle and nuclear physics

    J. Kristiano🇮🇩 · S. Clymton🇮🇩 · T. Mart🇮🇩

    We propose the use of pure spin-3/2 propagator in the $(3/2,0)\oplus (0,3/2)$ representation in particle and nuclear physics. To formulate the propagator in a covariant form we use the antisymmetric tensor spinor representation and we consider the $\Delta$ resonance contribution to the elastic $\pi N$ scattering as an example. We find that the use of conventional gauge invariant interaction Lagrangian leads to a problem; the obtained scattering amplitude does not exhibit the resonance behavior. To overcome this problem we modify the interaction by adding a momentum dependence. As in the case of Rarita-Schwinger we find that a perfect resonance description could be obtained in the pure spin-3/2 formulation only if hadronic form factors were considered in the interactions.

    ↳ nucl-thhep-phhep-thPRC(2017)·15 citations
28. 28*

    Flavor-singlet meson decay constants from $N_f=2+1+1$ twisted mass lattice QCD

    Konstantin Ottnad🇩🇪 · Carsten Urbach🇩🇪

    We present an improved analysis of our lattice data for the $\eta$--${\eta }^{\prime }$ system, including a correction of the relevant correlation functions for residual topological finite size effects and employing consistent chiral and continuum fits. From this analysis we update our physical results for the masses $M_{\eta }=557(11{)}_{\mathrm{stat}}(03{)}_{\chi \mathrm{PT}}\mathrm{MeV}$ and $M_{{\eta }^{\prime }}=911(64{)}_{\mathrm{stat}}(03{)}_{\chi \mathrm{PT}}\mathrm{MeV}$, as well as the mixing angle in the quark flavor basis $\varphi =38.8(2.2{)}_{\mathrm{stat}}(2.4{)}_{\chi \mathrm{PT}}^{\circ }$ in excellent agreement with other results from phenomenology. Similarly, we include an analysis for the decay constant parameters, leading to $f_l=125(5{)}_{\mathrm{stat}}(6{)}_{\chi \mathrm{PT}}\mathrm{MeV}$ and $f_s=178(4{)}_{\mathrm{stat}}(1{)}_{\chi \mathrm{PT}}\mathrm{MeV}$. The second error reflects the uncertainty related to the chiral extrapolation. The data used for this study has been generated on gauge ensembles provided by the European Twisted Mass Collaboration with $N_f=2+1+1$ dynamical flavors of Wilson twisted mass fermions. These ensembles cover a range of pion masses from $220\mathrm{MeV}$ to $500\mathrm{MeV}$ and three values of the lattice spacing. Combining our data with a prediction from chiral perturbation theory, we give an estimate for the physical $\eta ,{\eta }^{\prime }\to \gamma \gamma$ decay widths and the singly-virtual $\eta ,{\eta }^{\prime }\to \gamma {\gamma }^{\ast }$ transition form factors in the limit of large momentum transfer.

    ↳ hep-lathep-phPRD(2018)·60 citations
29. 29*

    Quasi-normal modes and absorption probabilities of spin-3/2 fields in $D$-dimensional Reissner-Nordström black hole spacetimes

    C.-H. Chen🇹🇼 · H. T. Cho🇹🇼 · A. S. Cornell🇿🇦 · G. Harmsen🇿🇦 · X. Ngcobo🇿🇦

    In this paper we consider spin-3/2 fields in a $D$-dimensional Reissner-Nordström black hole spacetime. As these spacetimes are not Ricci-flat, it is necessary to modify the covariant derivative to the supercovariant derivative, by including terms related to the background electromagnetic fields, so as to maintain the gauge symmetry. Using this supercovariant derivative we arrive at the corresponding Rarita-Schwinger equation in a charged black hole background. As in our previous works, we exploit the spherically symmetry of the spacetime and use the eigenspinor-vectors on an $N$-sphere to derive the radial equations for both non-transverse-traceless (non-TT) modes and TT modes. We then determine the quasi-normal mode and absorption probabilities of the associated gauge-invariant variables using the WKB approximation and the asymptotic iteration method. We then concentrate on how these quantities change with the charge of the black hole, especially when they reach the extremal limits.

    ↳ gr-qchep-phPRD(2018)·13 citations
30. 30*

    Octet Baryon Masses and Magnetic Moments in Hot and Dense Isospin Asymmetric Nuclear Matter

    Harpreet Singh🇮🇳 · Arvind Kumar🇮🇳 · Harleen Dahiya🇮🇳

    Medium modification of the magnetic moments of octet baryons in the isospin asymmetric nuclear medium at finite temperature has been calculated using medium modified quark and baryon masses derived in chiral SU(3) quark mean field model. The magnetic moments of baryons are found to vary significantly as a function of density of nuclear medium as well as with the increase in isospin asymmetry of the medium. The rise of temperature is found to decrease the effect of isospin asymmetry on masses and magnetic moments of baryons. The results of present investigation may be helpful to understand the experimentally observed values of octet baryon magnetic moments at different experimental facilities.

    ↳ nucl-thhep-phEur.Phys.J.Plus(2019)·20 citations
31. 31*

    Quantum Mechanics from Ergodic Average of Microstates

    Marco Matone🇮🇹

    We formulate quantum mechanics as an effective theory of an underlying structure characterized by microstates $|{\mathcal{M}}^j(t)⟩$, each one defined by the quantum state $|\Psi (t)⟩$ and a complete set of commutative observables $O^j$. At any time $t$, $|{\mathcal{M}}^j(t)⟩$ corresponds to a state $|O_k^j⟩$, for some $k$ depending on $t$, and jumps after time intervals whose duration, of the order of the Compton time $\tau$, is proportional to the probability $|⟨O_k^j|\Psi (t)⟩{|}^2$. This reproduces the Born rule and mimics the wave-particle duality. The theory is based on a partition of time whose flow is characterized by quantum probabilities. Ergodicity arises at ordinary quantum scales with the expectation values corresponding to time averaging over a period $\tau$. The measurement of $O^j$ provides a new partition of time and the outcome is the state $|O_k^j⟩$ to which $|{\mathcal{M}}^j(t)⟩$ corresponds at that time. The formulation, that shares some features with the path integral, can be tested by experiments involving time intervals of order $\tau$.

    ↳ quant-phcond-mat.stat-mechhep-phhep-th0 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.