Thu·Aug 15, 2019Thursday·August 15, 2019

1. 01*

   Completing the scalar and fermionic Universal One-Loop Effective Action

   Michael Krämer🇩🇪 · Benjamin Summ🇩🇪 · Alexander Voigt🇩🇪

   We extend the known Universal One-Loop Effective Action (UOLEA) by all operators which involve scalars and fermions, not including contributions arising from open covariant derivatives. Our generic analytic expressions for the one-loop Wilson coefficients of effective operators up to dimension six allow for an application of the UOLEA to a broader class of UV-complete models. We apply our generic results to various effective theories of supersymmetric models, where different supersymmetric particles are integrated out at a high mass scale.

   hep-phJHEP(2020)·76 citations
2. 02*

   Dark CP Violation and Gauged Lepton/Baryon Number for Electroweak Baryogenesis

   Marcela Carena🇺🇸 · Mariano Quirós🇪🇸 · Yue Zhang🇺🇸

   We explore the generation of the baryon asymmetry in an extension of the Standard Model where the lepton number is promoted to a $U(1{)}_{\ell }$ gauge symmetry with an associated $Z^{\prime }$ gauge boson. This is based on a novel electroweak baryogenesis mechanism first proposed by us in Ref. \cite{Carena:2018cjh}. Extra fermionic degrees of freedom - including a fermionic dark matter $\chi$ - are introduced in the dark sector for anomaly cancellation. Lepton number is spontaneously broken at high scale and the effective theory, containing the Standard Model, the $Z^{\prime }$, the fermionic dark matter, and an additional complex scalar field $S$, violates CP in the dark sector. The complex scalar field couples to the Higgs portal and is essential in enabling a strong first order phase transition. Dark CP violation is diffused in front of the bubble walls and creates a chiral asymmetry for $\chi$, which in turn creates a chemical potential for the Standard Model leptons. Weak sphalerons are then in charge of transforming the net lepton charge asymmetry into net baryon number. We explore the model phenomenology related to the leptophilic $Z^{\prime }$, the dark matter candidate, the Higgs boson and the additional scalar, as well as implications for electric dipole moments. We also discuss the case when baryon number $U(1{)}_B$ is promoted to a gauge symmetry, and discuss electroweak baryogenesis and its corresponding phenomenology.

   hep-phhep-exPRD(2020)·30 citations
3. 03*

   Exhaustive Model Selection in $b\to s\ell \ell$ Decays: Pitting Cross-Validation against AIC${}_c$

   Srimoy Bhattacharya🇮🇳 · Aritra Biswas🇮🇳 · Soumitra Nandi🇮🇳 · Sunando Kumar Patra🇮🇳

   In the light of recent data, we study the new physics effects in the exclusive $b\to s{\ell }^{+}{\ell }^{-}$ decays from a model independent perspective. Different combinations of the dimension six effective operators along with their respective Wilson coefficients are chosen for the analysis. To find out the operator or sets of operators that can best explain the available data in this channel, we simultaneously apply popular model selection tools like cross-validation and the information theoretic approach like Akaike Information Criterion (AIC). There are one, two, and three-operator scenarios which survive the test and a left-handed quark current with vector muon coupling is common among them. This is also the only surviving one-operator scenario. Best-fit values and correlations of the new Wilson coefficients are supplied for all the selected scenarios. We find that the angular observables play the dominant role in the model selection procedure. We also note that while a left-handed quark current with axial-vector muon coupling is the only one-operator scenario able to explain the ratios $R_{K^{(\ast )}}$ ($R_{K^{\ast }}$ for $q^2\in [0.045,1.1]{\mathrm{GeV}}^2$ in particular), there are also a couple of two operator scenarios that can simultaneously explain the measured $R_{K^{(\ast )}}$.

   hep-phhep-exPRD(2020)·32 citations
4. 04*

   Physics of parameter correlations around the solar-scale enhancement in neutrino theory with unitarity violation

   Ivan Martinez-Soler🇺🇸 · Hisakazu Minakata🇺🇸

   We discuss physics of the three neutrino flavor transformation with non-unitary mixing matrix, with particular attention to the correlation between the $\nu$SM- and the $\alpha$ parameters which represent effect of unitarity violating (UV) new physics. Toward the goal, a new perturbative framework is created to illuminate the effect of non-unitarity in region of the solar-scale enhanced oscillations. We refute the skepticism about the physical reality of the $\nu$SM CP $\delta$ - $\alpha$ parameter phase correlation by analysis with the SOL convention of $U_{\text{MNS}}$ in which $e^{\pm i\delta }$ is attached to $s_{12}$. Then, a comparative study between the solar- and atmospheric-scale oscillation regions allowed by the framework reveals a dynamical $\delta -$(blobs of the $\alpha$ parameters) correlation in the solar oscillation region, in sharp contrast to the ``chiral'' type phase correlation $[e^{-i\delta }{\bar{\alpha }}_{\mu e},e^{-i\delta }{\bar{\alpha }}_{\tau e},{\bar{\alpha }}_{\tau \mu }]$ in the PDG convention seen in the atmospheric oscillation region. An explicit perturbative calculation to first order in the ${\nu }_{\mu }\to {\nu }_e$ channel allows us to decompose the UV related part of the probability into the unitary evolution part and the genuine non-unitary part. We observe that the effect of non-unitarity tends to cancel between these two parts, as well as between the different ${\alpha }_{\beta \gamma }$ parameters.

   hep-phPTEP(2020)·12 citations
5. 05*

   Hyperon electromagnetic timelike elastic form factors at large $q^2$

   G. Ramalho🇧🇷 · M.T. Peña🇵🇹 · K. Tsushima🇧🇷

   We present estimates of the hyperon elastic form factors for the baryon octet and the ${\Omega }^{-}$ baryon for large four-momentum transfer squared, $q^2$, in the timelike region ($q^2>0$). Experimentally, those form factors can be extracted from the $e^{+}{e}^{-}\to B\bar{B}$ and $p\bar{p}\to B\bar{B}$ processes, where $B$ stands for a general baryon. Our results are based on calculations of the elastic electromagnetic form factors in the spacelike region ($Q^2=-q^2>0$) within a covariant quark model. To connect the results in the spacelike region to those in the timelike region, we use asymptotic relations between the two regions which are constraints derived from analyticity and unitarity. We calculate the effective form factors $|G(q^2)|$ and compare them with the integrated cross section data ${\sigma }_{\mathrm{Born}}(q^2)$ from BaBar, BES III, and CLEO. The available data are at the moment restricted to $\Lambda$, ${\Sigma }^0$, ${\Sigma }^{-}$, ${\Xi }^{-}$, ${\Xi }^0$, and ${\Omega }^{-}$ as well as to $e^{+}{e}^{-}\to \Lambda {\bar{\Sigma }}^0$ and $e^{+}{e}^{-}\to {\Sigma }^0\bar{\Lambda }$ reactions. Our results provide useful reference for future experiments and seem to indicate that the present data are still in the non-perturbative QCD region, while the onset for the asymptotic constraints from analyticity and unitarity happens much before the region of the perturbative QCD falloff of the form factors.

   hep-phhep-exnucl-exnucl-thPRD(2020)·39 citations
6. 06*

   Complete basis for the pentaquark wave function in a group theory approach

   Kai Xu🇹🇭 · Attaphon Kaewsnod🇹🇭 · Xuyang Liu🇹🇭 · Sorakrai Srisuphaphon🇹🇭 · Ayut Limphirat🇹🇭 · Yupeng Yan🇹🇭

   Permutation groups are applied to analyze the symmetries of pentaquark states. All possible quark configurations of the color, flavor, spin and spatial degrees of freedom are worked out in the language of permutation groups, and the corresponding wave functions are constructed systematically in the form of a Yamanouchi basis. The pentaquark spatial wave functions of various symmetries, which are derived in the harmonic-oscillator interaction, are applied as complete bases to evaluate the low-lying light $q^4\overline{q}$ pentaquark mass of all configurations, where the Cornell-like potential is employed.

   hep-phPRC(2019)·14 citations
7. 07*

   A QCD analysis for nuclear PDFs at NNLO

   Marina Walt🇩🇪 · Ilkka Helenius🇫🇮 · Werner Vogelsang🇩🇪

   A new QCD analysis for nuclear parton distribution functions (nPDFs) at next-to-leading order (NLO) and next-to-next-to-leading order (NNLO) is presented. The framework of the analysis, including the form of the parameterization as well as the included DIS data sets, are discussed. The results of this QCD analysis are compared to the existing nPDF sets and to the fitted data. The presented framework is based on an open-source tool, xFitter, which has been modified to be applicable also for a nuclear PDF analysis. The required modifications are covered as well. Finally, an outlook for the next developments of the QCD analysis for nuclear PDFs is given.

   hep-phPoS(2019)·1 citation
8. 08*

   The mass splitting among the isospin multiplets of light vector mesons

   Peng-Yu Niu🇨🇳 · Bin Zhou🇨🇳 · Qiang Zhao🇨🇳

   By including the strong isospin symmetry breaking effects and the electromagnetic contributions between the pseudoscalar mesons, we calculate the phase shifts of the $P$-wave $\pi \pi$ and $K\pi$ scattering up to $\mathcal{O}(p^4)$ in the framework of the SU(3) chiral perturbation theory (ChPT) and coupled channel inverse amplitude method. We re-fit the low energy constants with the present meson-meson scattering data and derive the mass differences for the charged and neutral iso-multiplets of $\rho$ and $K^{\ast }$. Our results show that the mass difference between ${\rho }^{\pm }$ and ${\rho }^0$ is very small while the mass difference between the charged and neutral $K^{\ast }$ can reach a relatively large value of $m_{K^{\ast 0}}-m_{K^{\ast +}}=2.91_{-1.41}^{+1.43}$ MeV. This full one-loop ChPT calculation would shed some light towards a better understanding of the long-standing puzzle about the $K^{\ast }$ mass splitting.

   hep-phhep-ex0 citations
9. 09*

   Spin Structure of heavy-quark hybrids

   Jaume Tarrús Castellà🇪🇸

   Exotic quarkonia are candidates to new types of hadrons including four quarks or gluonic degrees of freedom as constituents, the latter being a unique feature of QCD. We review recent developments in nonrelativistic EFTs to describe exotic quarkonia and in particular recent results on the spectrum of heavy hybrids including spin-dependent contributions up to $1/m_Q^2$-terms in the heavy-quark-mass expansion. We determine the nonperturbative contributions to the matching coefficients of the EFT by fitting our results to lattice-QCD determinations of the charmonium hybrid spectrum and extrapolate the results to the bottomonium hybrid sector where lattice-QCD determinations are still challenging. We also report on a recent new approach to quarkonium hadronic transitions that does not use the twist expansion and uses the hybrid spectrum as the intermediate octet states.

   hep-phhep-latAIP Conf.Proc.(2020)·10 citations
10. 10*

    New physics and tau $g-2$ using LHC heavy ion collisions

    Lydia Beresford🇬🇧 · Jesse Liu🇬🇧

    The anomalous magnetic moment of the tau lepton $a_{\tau }=(g_{\tau }-2)/2$ strikingly evades measurement, but is highly sensitive to new physics such as compositeness or supersymmetry. We propose using ultraperipheral heavy ion collisions at the LHC to probe modified magnetic $\delta a_{\tau }$ and electric dipole moments $\delta d_{\tau }$. We introduce a suite of one electron/muon plus track(s) analyses, leveraging the exceptionally clean photon fusion $\gamma \gamma \to \tau \tau$ events to reconstruct both leptonic and hadronic tau decays sensitive to $\delta a_{\tau },\delta d_{\tau }$. Assuming 10% systematic uncertainties, the current 2 nb${}^{-1}$ lead-lead dataset could already provide constraints of $-0.0080<a_{\tau }<0.0046$ at 68% CL. This surpasses 15 year old lepton collider precision by a factor of three while opening novel avenues to new physics.

    hep-phhep-exPRD(2020)·91 citations
11. 11*

    Polarization fraction measurement in ZZ scattering using deep learning

    Junho Lee🇨🇳 · Nicolas Chanon🇫🇷 · Andrew Levin🇨🇳 · Jing Li🇨🇳 · Meng Lu🇨🇳 · Qiang Li🇨🇳 · Yajun Mao🇨🇳

    Measuring longitudinally polarized vector boson scattering in the ZZ channel is a promising way to investigate unitarity restoration with the Higgs mechanism and to search for possible new physics. We investigated several deep neural network structures and compared their ability to improve the measurement of the longitudinal fraction Z_L Z_L. Using fast simulation with the Delphes framework, a clear improvement is found using a previously investigated 'particle-based' deep neural network on a preprocessed dataset and applying principle component analysis to the outputs.A significance of around 1.7 standard deviations can be achieved with the integrated luminosity of 3000 fb-1 that will be recorded at the High-Luminosity LHC.

    hep-phhep-exPRD(2019)·20 citations
12. 12*

    Helical phase inflation and its observational constraints

    Mudassar Sabir🇨🇳 · Waqas Ahmed🇨🇳 · Yungui Gong🇨🇳 · Tianjun Li🇨🇳 · Jiong Lin🇨🇳

    We consider a class of helical phase inflation models from the $\mathcal{N}=1$ supergravity where the phase component of a complex field acts as an inflaton. This class of models avoids the eta problem in supergravity inflation due to the phase monodromy of the superpotential. We study the inflationary predictions of this class of models in the context of both standard and large extra dimensional brane cosmology, and find that they can easily accommodate the Planck 2018 and BICEP2 constraints. We find that the helical phase inflation has $\alpha$-attractors and the attractors depend on one model parameter only.

    hep-phgr-qcJCAP(2020)·8 citations
13. 13*

    A light CP-odd Higgs boson of the MSSM Higgs sector extended by dimension-six operators

    Mikhail Dubinin🇷🇺 · Elena Fedotova (Skobeltsyn Institute of Nuclear Physics, Lomonosov Moscow State University)🇷🇺

    The possibility of identification of an observable CMS ${\mu }^{+}{\mu }^{-}$ excess at 28 GeV in the channel $pp\to {\mu }^{+}{\mu }^{-}b\bar{b}$ at $\sqrt{s}$=8 TeV and 13 TeV as a manifestation of one of the minimal supersymmetric standard model (MSSM) Higgs bosons is investigated. The MSSM parametric scenarios in the regime of large threshold corrections involving low-mass CP-odd scalar, a 125 GeV CP-even scalar and other Higgs bosons with suitable masses are found, where the alignment limit conditions for the Higgs couplings are respected. Perturbative unitarity bounds and constraints on the electroweak vacuum stability are discussed in the regime of substantial couplings with the top- and bottom superpartners. LHC phenomenology including top-quark decay in such a regime is analyzed.

    hep-ph0 citations
14. 14*

    Towards a generic implementation of matrix-element maximisation as a classifier in particle physics

    Stefan von Buddenbrock🇿🇦 · Olivier Mattelaer🇧🇪 · Michael Spannowsky🇬🇧

    The so-called matrix-element method (MEM) has long been used successfully as a classification tool in particle physics searches. In the presence of invisible final state particles, the traditional MEM typically assigns probabilities to an event -- based on whether it is more signal or background-like -- through a phase space integration over all degrees of freedom of the invisible particles in the process(es). One inherent shortcoming of the traditional MEM is that the phase space integration can be slow, and therefore impractical for high multiplicity final states and/or large data sets. The recent alternative of matrix-element maximisation has recently been introduced to circumvent this problem, since maximising a highly-dimensional function can be a far more CPU-efficient task than that of integration. In this work, matrix-element maximisation is applied to the process of fully-leptonic top associated Higgs production, where the Higgs boson decays to two $b$-quarks. A variety of optimisation algorithms are tested in terms of their performance and speed, and it is explicitly found that the maximisation technique is far more CPU-efficient than the traditional MEM at the cost of a slight reduction in performance. An interesting consequence of using matrix-element maximisation is that the result of the procedure gives an estimate of the four-momenta for the invisible particles in the event. As a result, the idea of using these estimates as input information for more complicated tools is discussed with potential prospects for future developments of the method.

    hep-ph1 citation
15. 15*

    Dynamical Derivation of the Momentum Space Shell Structure for Quarkyonic Matter

    Kie Sang Jeong🇺🇸 · Larry McLerran🇺🇸 · Srimoyee Sen🇺🇸

    The phase space structure of zero temperature Quarkyonic Matter is a Fermi sphere of Quark Matter, surrounded by a shell of Nucleonic Matter. We construct a quasi particle model of Quarkyonic Matter based on the constituent quark model, where the quark and nucleon masses are related by m_Q = m_N/N_c, and N_c is the number of quark colors. The region of occupied states is for quarks k_Q < k_F/N_c, and for nucleons k_F < k_N < k_F + \Delta. We first consider the general problem of Quarkyonic Matter with hard core nucleon interactions. We then specialize to a quasi-particle model where the hard core nucleon interactions are accounted for by an excluded volume. In this model, we show that the nucleonic shell forms past some critical density related to the hard core size, and for large densities becomes a thin shell. We explore the basic features of such a model, and argue this model has the semi-quantitative behaviour needed to describe neutron stars.

    ↳ nucl-thastro-ph.HEhep-phPRC(2020)·115 citations
16. 16*

    DGLAP and BFKL equations in $\mathcal{N}=4$ SYM: from weak to strong coupling

    A.V. Kotikov🇷🇺 · A.I. Onishchenko🇷🇺

    DGLAP and BFKL equations are among the cornestones of the contemporary QCD. Moreover, they also played an important role in the recent studies of integrability structure of $\mathcal{N}=4$ SYM. Here, we review the results obtained along this way together with a brief account of approaches and methods used.

    ↳ hep-thhep-ph7 citations
17. 17*

    Single-Energy Partial Wave Analysis for ${\pi }^0$ Photoproduction on Proton with Fixed-$t$ Analyticity Imposed

    H. Osmanović🇧🇦 · M. Hadžimehmedović🇧🇦 · R. Omerović🇧🇦 · J. Stahov🇧🇦 · M. Gorchtein🇩🇪 · V. Kashevarov🇩🇪 · K. Nikonov🇩🇪 · M. Ostrick🇩🇪 · L. Tiator🇩🇪 · A. Švarc🇭🇷

    High precision data of the $\gamma p\to {\pi }^{0}p$ reaction from its threshold up to $W=2$~GeV have been used in order to perform a single-energy partial wave analysis with minimal model dependence. Continuity in energy was achieved by imposing constraints from fixed-$t$ analyticity in an iterative procedure. Reaction models were only used as starting point in the very first iteration. We demonstrate that with this procedure partial wave amplitudes can be obtained which show only a minimal dependence on the initial model assumptions.

    ↳ nucl-thhep-phPRC(2019)·9 citations
18. 18*

    New Limits on Charged Dark Matter from Large-Scale Coherent Magnetic Fields

    Albert Stebbins🇺🇸 · Gordan Krnjaic🇺🇸

    We study the interaction of an electrically charged component of the dark matter with a magnetized galactic interstellar medium (ISM) of (rotating) spiral galaxies. For the observed ordered component of the field, $B\sim \mu$G, we find that the accumulated Lorentz interactions between the charged particles and the ISM will extract an order unity fraction of the disk angular momentum over the few Gyr Galactic lifetime unless $q/e\lesssim 10^{-13\pm 1}m{c}^2/$ GeV if all the dark matter is charged. The bound is weakened by factor $f_{\mathrm{qdm}}^{-1/2}$ if only a mass fraction $f_{\mathrm{qdm}}\gtrsim 0.13$ of the dark matter is charged. Here $q$ and $m$ are the dark matter particle mass and charge. If $f_{\mathrm{qdm}}\approx 1$ this bound excludes charged dark matter produced via the freeze-in mechanism for $m\lesssim$ TeV/$c^2$. This bound on $q/m$, obtained from Milky Way parameters, is rough and not based on any precise empirical test. However this bound is extremely strong and should motivate further work to better model the interaction of charged dark matter with ordered and disordered magnetic fields in galaxies and clusters of galaxies; to develop precise tests for the presence of charged dark matter based on better estimates of angular momentum exchange; and also to better understand how charged dark matter might modify the growth of magnetic fields, and the formation and interaction histories of galaxies, galaxy groups, and clusters.

    ↳ astro-ph.COastro-ph.GAhep-phJCAP(2019)·48 citations
19. 19*

    Nucleon-to-Resonance Form Factors at Large Photon Virtualities

    J. Segovia🇪🇸 · C. Chen🇩🇪 · Z.-F. Cui🇨🇳 · Y. Lu🇨🇳 · C.D. Roberts🇺🇸

    We present a unified description of elastic and transition form factors involving the nucleon and its resonances; in particular, the $N(1440)$, $\Delta (1232)$ and $\Delta (1600)$. We compare predictions made using a framework built upon a Faddeev equation kernel and interaction vertices that possess QCD-kindred momentum dependence with results obtained using a confining, symmetry-preserving treatment of a vector$\otimes$vector contact-interaction in a widely-used leading-order (rainbow-ladder) truncation of QCD's Dyson-Schwinger equations. This comparison explains that the contact-interaction framework produces hard form factors, curtails some quark orbital angular momentum correlations within a baryon, and suppresses two-loop diagrams in the elastic and transition electromagnetic currents. Such defects are rectified in our QCD-kindred framework and, by contrasting the results obtained for the same observables in both theoretical schemes, shows those objects which are most sensitive to the momentum dependence of elementary quantities in QCD.

    ↳ nucl-thhep-exhep-lathep-ph+1AIP Conf.Proc.(2020)·6 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.