Mon·Aug 13, 2018Monday·August 13, 2018

1. 01*

   Two-component dark matter and a massless neutrino in a new B-L model

   Nicolas Bernal🇨🇴 · Diego Restrepo🇨🇴 · Carlos Yaguna🇨🇴 · Oscar Zapata🇨🇴

   We propose a new extension of the Standard Model by a $U(1{)}_{B-L}$ gauge symmetry in which the anomalies are canceled by two right-handed neutrinos plus four chiral fermions with fractional B-L charges. Two scalar fields that break the B-L symmetry and give masses to the new fermions are also required. After symmetry breaking, two neutrinos acquire Majorana masses via the seesaw mechanism leaving a massless neutrino in the spectrum. Additionally, the other new fermions arrange themselves into two Dirac particles, both of which are automatically stable and contribute to the observed dark matter density. This model thus realizes in a natural way, without ad hoc discrete symmetries, a two-component dark matter scenario. We analyze in some detail the dark matter phenomenology of this model. The dependence of the relic densities with the parameters of the model is illustrated and the regions consistent with the observed dark matter abundance are identified. Finally, we impose the current limits from LHC and direct detection experiments, and show that the high mass region of this model remains unconstrained.

   hep-phPRD(2019)·54 citations
2. 02*

   Generalized distribution amplitudes and gravitational form factors for pion

   Qin-Tao Song🇯🇵

   Generalized parton distributions (GPDs) have been investigated in the deeply virtual Compton scattering (DVCS) to solve the proton spin puzzle. On the other hand, the generalized distribution amplitudes (GDAs) can be studied in the two-photon process ${\gamma }^{\ast }\gamma \to h\bar{h}$ which is accessible at KEKB. Namely, the GDAs are the $s$-$t$ crossed quantities of the GPDs. In 2016, the differential cross section of the process ${\gamma }^{\ast }\gamma \to {\pi }^0{\pi }^0$ was measured by the Belle collaboration in the $e^{+}{e}^{-}$collision , so that the pion GDAs can be obtained by analyzing the Belle data. Expressing the GDAs with a few parameters, we determined the GDAs by a ${\chi }^2$ analysis . The form factors of the quark energy-momentum tensor are obtained from the determined GDAs. Then, we calculated the mass radius as 0.56-0.69 fm for the pion by using the form factor. This is the first study on gravitational form factors and radius of hadrons from actual experimental measurements . The Belle II will start taking data in 2018 by the upgraded SuperKEKB. Therefore, much accurate data are expected for the pion, and other hadron-pair productions will be measured in the near future. The GDA studies are valuable for understanding not only the 3D structure but also gravitational properties of hadrons.

   hep-phhep-exhep-latnucl-thPoS(2018)·1 citation
3. 03*

   Renormalization of mixing angles

   Ansgar Denner🇩🇪 · Stefan Dittmaier🇩🇪 · Jean-Nicolas Lang🇨🇭

   We discuss the renormalization of mixing angles for theories with extended scalar sectors. Motivated by shortcomings of existing schemes for mixing angles, we review existing renormalization schemes and introduce new ones based on on-shell conditions or symmetry requirements such as rigid or background-field gauge invariance. Considering in particular the renormalization of the mixing angles in the Two-Higgs-Doublet Model and the Higgs-Singlet Extension of the Standard Model, we compare electroweak corrections within these models for a selection of renormalization schemes. As specific examples, we present next-to-leading-order results on the four-fermion decays of heavy and light CP-even Higgs bosons, $H_1/H_2\to WW/ZZ\to 4f$, and on electroweak Higgs-boson production processes, i.e. Higgs-strahlung and vector-boson fusion. We find that our new proposals for on-shell and symmetry-based renormalization conditions are well-behaved for the considered benchmark scenarios in both models.

   hep-phJHEP(2018)·87 citations
4. 04*

   Long-distance QCD effects in FCNC $B\to \gamma l^{+}{l}^{-}$ decays

   Anastasiia Kozachuk🇷🇺 · Dmitri Melikhov🇦🇹 · Nikolai Nikitin🇷🇺

   This presentation reviews the main results of our recent work [A.K., D.M., N.N., Phys. Rev. D97, 053007 (2018)] on rare radiative leptonic decays $B_{d,s}\to \gamma {\mu }^{+}{\mu }^{-}$ and $B_{d,s}\to \gamma e^{+}{e}^{-}$ induced by flavour-changing neutral currents (FCNC) in the Standard Model.

   hep-phEPJ Web Conf.(2018)·2 citations
5. 05*

   Footprints of New Physics in $b\to c\tau \nu$ Transitions

   Zhuo-Ran Huang🇨🇳 · Ying Li🇨🇳 · Cai-Dian Lu🇨🇳 · M. Ali Paracha🇵🇰 · Chao Wang🇨🇳

   In this work, we perform a combined analysis of the $R(D)$, $R(D^{\ast })$, and $R(J/\psi )$ anomalies in a model-independent manner based on the general framework of the four-fermion effective field theory, paying special attention to the use of the hadronic form factors. For the $B\to D(D^{\ast })$ transition form factors, we use the HQET parametrization that includes the higher order corrections of $\mathcal{O}({\alpha }_s,{\Lambda }_{\mathrm{QCD}}/m_{b,c})$ and was determined recently from a fit to lattice QCD and light-cone sum rule results in complementary kinematical regions of the momentum transfer. For the $B_c\to J/\psi ({\eta }_c)$ transitions, we use the form factors calculated in the covariant light-front quark model, which are found to be well consistent with the preliminary lattice results. With this particular treatment of hadronic matrix elements, in our analysis the two classes of vector operators are shown to be the most favored single new physics (NP) operators by the current experimental constraints within $2\sigma$ and the LEP1 data on $Br(B_c\to \tau \nu )$ as well as the minimum ${\chi }^2$ fit, while the tensor operator is also allowed but severely constrained, and the scalar ones are excluded. Using the favored ranges and fitted values of the Wilson coefficients of the single NP operators, we also give a prognosis for the physical observables such as the ratios of decay rates ($R(D(D^{\ast })),R(J/\psi ({\eta }_c))$) and other polarized observables as well as the $q^2$ distributions.

   hep-phPRD(2018)·127 citations
6. 06*

   New physics from TOTEM's recent measurements of elastic and total cross sections

   István Szanyi🇺🇦 · Norbert Bence🇺🇦 · László Jenkovszky🇺🇦

   We analyze the recently discovered phenomena in elastic proton-proton scattering at the LHC, challenging the standard Regge-pole theory: the low-$|t|$ "break" (departure from the exponential behavior of the diffraction cone), the accelerating rise with energy of the forward slope $B(s,t=0)$, the absence of secondary dips and bumps on the cone and the role of the odderon in the forward phase of the amplitude, $\rho (13TeV)=0.1\pm 0.01$, and especially its contribution at the dip region, measured recently by TOTEM. Relative contributions from different components to the scattering amplitude are evaluated from the fitted model.

   hep-phJ.Phys.G(2019)·15 citations
7. 07*

   Prospects of detecting dark matter through cosmic-ray antihelium with the antiproton constraints

   Yu-Chen Ding🇨🇳 · Nan Li🇨🇳 · Chun-Cheng Wei🇨🇳 · Yue-Liang Wu🇨🇳 · Yu-Feng Zhou🇨🇳

   Cosmic-ray (CR) antihelium is an important observable for dark matter (DM) indirect searches due to extremely low secondary backgrounds towards low energies. In a given DM model, the predicted CR antihelium flux is expected to be strongly correlated with that of CR antiprotons. In this work, we use the AMS-02 $\bar{p}/p$ data to constrain the DM annihilation cross section, and the ALICE data on the ${}^3\overline{\text{He}}$ and $\overline{\text{T}}$ productions to determine the parameters in the coalescence model for anti-nucleus formation. The hadronic cross sections are estimated using Monte-Carlo event generators including $\text{EPOS-LHC}$ and $\text{DPMJET}$. Based on these constraints, we make predictions for the maximal antihelium flux for typical DM annihilation final states, and perform a detailed analysis on the uncertainties due to the DM density profiles and CR propagation models. We find that the results are highly insensitive to both of them, but still significantly depends on the hadronization models in event generators. The prospects of detecting antihelium for the AMS-02 experiment is discussed. We show that with very optimistic assumptions, CR ${}^3\overline{\text{He}}$ is within the reach of the AMS-02 experiment. The ${}^3\overline{\text{He}}$ events which can be detected by AMS-02 are likely to have kinetic energy $T\gtrsim 30$~GeV, which is consistent with the preliminary AMS-02 search results. The events which can be observed by AMS-02 are likely to arise dominantly from secondary backgrounds rather than DM interactions.

   hep-phJCAP(2019)·25 citations
8. 08*

   Let there be Light Dark Matter: The gauged $U(1{)}_{L_{\mu }-L_{\tau }}$ case

   Patrick Foldenauer🇩🇪

   As experimental null results increase the pressure on heavy weakly interacting massive particles (WIMPs) as an explanation of thermal dark matter (DM), it seems timely to explore previously overlooked regions of the WIMP parameter space. In this work we extend the minimal gauged $U(1{)}_{L_{\mu }-L_{\tau }}$ model studied in \cite{Bauer:2018onh} by a light (MeV-scale) vector-like fermion $\chi$. Taking into account constraints from cosmology, direct and indirect detection we find that the standard benchmark of $M_V=3m_{\chi }$ for DM coupled to a vector mediator is firmly ruled out for unit DM charges. However, exploring the near-resonance region $M_V\gtrsim 2m_{\chi }$ we find that this model can simultaneously explain the DM relic abundance $\Omega h^2=0.12$ and the $(g-2{)}_{\mu }$ anomaly. Allowing for small charge hierarchies of $\lesssim \mathcal{O}(10)$, we identify a second window of parameter space in the few-GeV region, where $\chi$ can account for the full DM relic density.

   hep-phPRD(2019)·109 citations
9. 09*

   Shedding Light on Top Partner at the LHC

   Haider Alhazmi🇺🇸 · Jeong Han Kim🇺🇸 · Kyoungchul Kong🇺🇸 · Ian M. Lewis🇺🇸

   We investigate the sensitivity of the 14 TeV LHC to pair-produced top partners ($T$) decaying into the Standard Model top quark ($t$) plus either a gluon ($g$) or a photon ($\gamma$). The decays $T\to tg$ and $T\to t\gamma$ can be dominant when the mixing between the top partner and top quark are negligible. In this case, the conventional decays $T\to bW$, $T\to tZ$, and $T\to th$ are highly suppressed and can be neglected. We take a model-independent approach using effective operators for the $T$-$t$-$g$ and $T$-$t$-$\gamma$ interactions, considering both spin-$\frac{1}{2}$ and spin-$\frac{3}{2}$ top partners. We perform a semi-realistic simulation with boosted top quark tagging and an appropriate implementation of a jet-faking-photon rate. Despite a simple dimensional analysis indicating that the branching ratios $\mathrm{BR}(T\to t\gamma )\ll \mathrm{BR}(T\to tg)$ due to the electric-magnetic coupling being much smaller than the strong force coupling, our study shows that the LHC sensitivity to $T\bar{T}\to t\overline{t}\gamma g$ is more significant than the sensitivity to $T\overline{T}\to t\overline{t}gg$. This is due to much smaller backgrounds attributed to the isolated high-$p_T$ photon. We find that with these decay channels and 3 ab${}^{-1}$ of data, the LHC is sensitive to top partner masses $m_T\lesssim 1.4-1.8$~TeV for spin-$\frac{1}{2}$ and spin-$\frac{3}{2}$ top partners, respectively.

   hep-phJHEP(2019)·42 citations
10. 10*

    Non-Standard Interactions and Prospects for Studying Standard Parameter Degeneracies in DUNE and T2HKK

    Surender Verma🇮🇳 · Shankita Bhardwaj🇮🇳

    The future long baseline experiments such as DUNE and T2HKK have promising prospects to determine the neutrino mass hierarchy and measuring standard $CP$ phase $\delta$. However, presence of possible non-standard interactions of neutrinos with matter may intricate this picture and is the subject matter of the present work. We have studied the standard parameter degeneracies in presence of non-standard interactions(NSI) with DUNE and T2HKK experiments. We examine the mass hierarchy degeneracy assuming (i) all NSI parameters to be non-zero and (ii) one NSI parameter(${ϵ}_{e\mu }$) and its corresponding $CP$ phase(${\delta }_{e\mu }$) to be non-zero. We find that the later case is more appropriate to resolve mass hierarchy degeneracy with DUNE and T2HKK experiments due to relatively small uncertainties emanating from the NSI sector. We have, also, investigated the octant degeneracy with neutrino(${\nu }_{\mu }\to {\nu }_e$) and antineutrino(${\bar{\nu }}_{\mu }\to {\bar{\nu }}_e$) mode separately. We find that to resolve this degeneracy the long baseline experiment with combination of neutrino and antineutrino mode is essential. Furthermore, we have considered DUNE in conjunction with T2HKK experiment to study $CP$ phase degeneracy due to standard($\delta$) and non-standard(${\delta }_{e\mu }$) $CP$ phases. We find that DUNE and T2HKK, in conjunction, has more sensitivity for $CP$ violation effects(10$\sigma$ for true NH and 8.2$\sigma$ for true IH).

    hep-phAdv.High Energy Phys.(2019)·16 citations
11. 11*

    Reheating and Entropy Perturbations in Fibre Inflation

    Bao-Min Gu🇨🇳 · Robert Brandenberger🇨🇦

    We study reheating in some one and two field realizations of {\it Fibre Inflation}. We find that reheating begins with a phase of preheating in which long wavelength fluctuation modes are excited. In two field models there is a danger that the parametric amplification of infrared fluctuations in the second scalar field - associated with an entropy mode - might induce an instability of the curvature fluctuations. We show that, at least in the models we consider, the entropy mode has a sufficiently large mass to prevent this instability. Hence, from the point of view of reheating the models we consider are well-behaved.

    ↳ hep-thastro-ph.COgr-qchep-phCPC(2020)·19 citations
12. 12*

    Prospects for Measurements with Strange Hadrons at LHCb

    A. A. Alves Junior🇪🇸 · M. O. Bettler🇬🇧 · A. Brea Rodríguez🇪🇸 · A. Casais Vidal🇪🇸 · V. Chobanova🇪🇸 · X. Cid Vidal🇪🇸 · A. Contu🇮🇹 · G. D'Ambrosio🇮🇹 · J. Dalseno🇪🇸 · F. Dettori🇬🇧 · V.V. Gligorov🇫🇷 · G. Graziani🇮🇹 and 14 other authors

    This report details the capabilities of LHCb and its upgrades towards the study of kaons and hyperons. The analyses performed so far are reviewed, elaborating on the prospects for some key decay channels, while proposing some new measurements in LHCb to expand its strangeness research program.

    ↳ hep-exhep-phJHEP(2019)·96 citations
13. 13*

    Enhanced nuclear Schiff moment and time reversal violation in 229Th-containing molecules

    V.V. Flambaum🇦🇺

    Octupole deformation results in a strongly enhanced collective Schiff moment in 229Th nucleus. An additional enhancement of time reversal (T) and parity (P) violating effects (such as T,P-violating electric dipole moments) appears in the ground 1Sigma state and in the metastable 3Delta_1 state of diatomic molecule 229ThO. Similar enhancements exist in molecular ions 229ThOH+, 229ThF+ and 225,223RaOH+. Corresponding experiments may be used to test CP-violation theories predicting T,P-violating nuclear forces and to search for axions.

    ↳ physics.atom-phhep-phnucl-thPRC(2019)·52 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.