Wed·Mar 28, 2018Wednesday·March 28, 2018

1. 01*

   Gauge-Yukawa theories: Beta functions at large $N_f$

   Oleg Antipin🇭🇷 · Nicola Andrea Dondi🇩🇰 · Francesco Sannino🇩🇰 · Anders Eller Thomsen🇩🇰 · Zhi-Wei Wang🇩🇰

   We consider the dynamics of gauge-Yukawa theories in the presence of a large number of matter constituents. We first review the current status for the renormalization group equations of gauge-fermion theories featuring also semi-simple groups. In this regime these theories develop an interacting ultraviolet fixed point that for the semi-simple case leads to a rich phase diagram. The latter contains a complete asymptotically safe fixed point repulsive in all couplings. We then add two gauged Weyl fermions belonging to arbitrary representations of the gauge group and a complex, gauged scalar to the original gauge-fermion theory allowing for new Yukawa interactions and quartic scalar self-coupling. Consequently, we determine the leading $1/N_f$ Yukawa and quartic beta functions. Our work elucidates, consolidates and extends results obtained earlier in the literature. We also acquire relevant knowledge about the dynamics of gauge-Yukawa theories beyond perturbation theory. Our findings are applicable to any extension of the standard model featuring a large number of fermions such as asymptotic safety.

   hep-phhep-thPRD(2018)·47 citations
2. 02*

   SUSY Confinement

   Shu-Min Zhao🇨🇳 · Xue-Qian Li🇨🇳

   In response to the present status that searching for SUSY particles has been unsuccessful, we propose a bold scenario that SUSY particles are confined inside hadrons with a required condition of $P_R=1$ in analog to the color confinement for quarks. The scenario seems to be able to reconcile the beautiful SUSY theory and non-observation at present experiments. On other aspects, some loopholes in the proposal emerge and require to be answered in the future research.

   hep-phCommun.Theor.Phys.(2018)·0 citations
3. 03*

   Two loop electroweak corrections to $\bar{B}\to X_s\gamma$ and $B_s^0\to {\mu }^{+}{\mu }^{-}$ in the B-LSSM

   Jin-Lei Yang · Tai-Fu Feng🇨🇳 · Hai-Bin Zhang🇨🇳 · Rong-Fei Zhu🇨🇳 · Shu-Min Zhao🇨🇳 · Xiu-Yi Yang

   The rare decays $\bar{B}\to X_s\gamma$ and $B_s^0\to {\mu }^{+}{\mu }^{-}$ are important to research new physics beyond standard model. In this work, we investigate two loop electroweak corrections to $\bar{B}\to X_s\gamma$ and $B_s^0\to {\mu }^{+}{\mu }^{-}$ in the minimal supersymmetric extension of the SM with local $B-L$ gauge symmetry (B-LSSM), under a minimal flavor violating assumption for the soft breaking terms. In this framework, new particles and new definition of squarks can affect the theoretical predictions of these two processes, with respect to the MSSM. Considering the constraints from updated experimental data, the numerical results show that the B-LSSM can fit the experimental data for the branching ratios of $\bar{B}\to X_s\gamma$ and $B_s^0\to {\mu }^{+}{\mu }^{-}$. The results of the rare decays also further constrain the parameter space of the B-LSSM.

   hep-phEPJC(2018)·49 citations
4. 04*

   Hard Photons in Hadroproduction of Top Quarks with Realistic Final States

   G. Bevilacqua🇭🇺 · H. B. Hartanto🇬🇧 · M. Kraus🇩🇪 · T. Weber🇩🇪 · M. Worek🇩🇪

   We present a complete description of top quark pair production in association with a hard photon in the dilepton channel. Our calculation is accurate to NLO in QCD. It is based on matrix elements for $e^{+}{\nu }_e{\mu }^{-}{\bar{\nu }}_{\mu }b\bar{b}\gamma$ production and includes all resonant and non-resonant diagrams, interferences, and off-shell effects of the top quarks and the $W$ gauge bosons. This calculation constitutes the first full computation for top quark pair production with a final state photon in hadronic collisions at NLO in QCD. Numerical results for total and differential cross sections are presented for the LHC at a centre-of-mass energy of $\sqrt{s}=13$ TeV. For a few observables relevant for new physics searches, beyond some kinematic bounds, we observe shape distortions of more than $100\%$. In addition, we confirm that the size of the top quark off-shell effects for the total cross section is consistent with the expected uncertainties of the narrow width approximation. Results presented here are not only relevant for beyond the Standard Model physics searches but also important for precise measurements of the top-quark fiducial cross sections and top-quark properties at the LHC.

   hep-phhep-exJHEP(2018)·76 citations
5. 05*

   N3LO Corrections to Jet Production in Deep Inelastic Scattering using the Projection-to-Born Method

   J. Currie🇬🇧 · T. Gehrmann🇨🇭 · E.W.N. Glover🇬🇧 · A. Huss🇨🇭 · J. Niehues🇬🇧 · A. Vogt🇬🇧

   Computations of higher-order QCD corrections for processes with exclusive final states require a subtraction method for real-radiation contributions. We present the first-ever generalisation of a subtraction method for third-order (N3LO) QCD corrections. The Projection-to-Born method is used to combine inclusive N3LO coefficient functions with an exclusive second-order (NNLO) calculation for a final state with an extra jet. The input requirements, advantages, and potential applications of the method are discussed, and validations at lower orders are performed. As a test case, we compute the N3LO corrections to kinematical distributions and production rates for single-jet production in deep inelastic scattering in the laboratory frame, and compare them with data from the ZEUS experiment at HERA. The corrections are small in the central rapidity region, where they stabilize the predictions to sub per-cent level. The corrections increase substantially towards forward rapidity where large logarithmic effects are expected, thereby yielding an improved description of the data in this region.

   hep-phJHEP(2018)·102 citations
6. 06*

   Correlation functions of three-dimensional Yang-Mills theory from the FRG

   Lukas Corell🇩🇪 · Anton K. Cyrol🇩🇪 · Mario Mitter🇺🇸 · Jan M. Pawlowski🇩🇪 · Nils Strodthoff🇺🇸

   We compute correlation functions of three-dimensional Landau-gauge Yang-Mills theory with the Functional Renormalisation Group. Starting from the classical action as only input, we calculate the non-perturbative ghost and gluon propagators as well as the momentum-dependent ghost-gluon, three-gluon, and four-gluon vertices in a comprehensive truncation scheme. Compared to the physical case of four spacetime dimensions, we need more sophisticated truncations due to significant contributions from non-classical tensor structures. In particular, we apply a special technique to compute the tadpole diagrams of the propagator equations, which captures also all perturbative two-loop effects, and compare our correlators with lattice and Dyson-Schwinger results.

   hep-phhep-lathep-thSciPost Phys.(2018)·82 citations
7. 07*

   21cm absorption signal from charge sequestration

   Adam Falkowski🇫🇷 · Kalliopi Petraki🇫🇷

   The unexpectedly strong 21cm absorption signal detected by the EDGES experiment suggests that the baryonic gas was colder at redshift $z\sim 17$ than predicted in the standard scenario. We discuss a mechanism to lower the baryon temperature after recombination. We introduce a stable, negatively-charged particle with a non-negligible cosmological abundance, such that the universe remains charge-neutral but the electron and proton numbers are no longer equal. The deficit of electrons during recombination results in an earlier decoupling of the baryon gas temperature from that of the CMB. This implies a smaller ratio of the gas and CMB temperature at $z\sim 17$. The parameter space of the mechanism where the 21 cm absorption signal is significantly enhanced is probed by the CMB spectrum, cooling of stars and supernovae, and colliders. Nevertheless, we find viable regions corresponding to sub-eV or MeV-scale milli-charged particles, or to TeV-scale multi-charged particles.

   hep-phastro-ph.CO33 citations
8. 08*

   PSI/UZH Workshop: Impact of $B\to {\mu }^{+}{\mu }^{-}$ on New Physics Searches

   A. Crivellin🇨🇭 · M. Ghezzi🇨🇭 · D. Müller🇨🇭 · A. Signer🇨🇭 · Y. Ulrich🇨🇭 · F. Bernlochner🇩🇪 · I. de Medeiros Varzielas🇵🇹 · S. Descotes-Genon🇫🇷 · M. Fael🇩🇪 · D. Ghosh🇮🇱 · A. Greljo🇨🇭 · M. Hoferichter🇺🇸 and 9 other authors

   In these mini-proceedings we review the results of the workshop `Impact of $B\to {\mu }^{+}{\mu }^{-}$ on New Physics Searches' that took place at the Paul Scherrer Institute (PSI) on the 18th-19th December 2017.

   hep-phhep-ex9 citations
9. 09*

   Seeking leptoquarks in IceCube

   Damir Bečirević🇫🇷 · Boris Panes🇧🇷 · Olcyr Sumensari🇮🇹 · Renata Zukanovich Funchal🇧🇷

   We investigate the sensitivity of IceCube(-Gen2) to a scalar leptoquark scenario with couplings only to heavy quark flavors which may be connected to solving discrepancies in $B$-meson semileptonic decays. We take into account, for the first time, the non-negligible neutrino-gluon cross section induced by leptoquarks, and we systematically account for indirect and direct constraints which have been overlooked in previous studies. We conclude that IceCube(-Gen2) can only probe the light LQ regime, already disfavored by the combination of flavor physics constraints, electroweak precision data and the direct searches at the LHC.

   hep-phJHEP(2018)·41 citations
10. 10*

    Dark Matter in the Standard Model?

    Christian Gross🇮🇹 · Antonello Polosa🇮🇹 · Alessandro Strumia🇮🇹 · Alfredo Urbano🇨🇭 · Wei Xue🇨🇭

    We critically reexamine two possible Dark Matter candidate within the Standard Model. First, we consider the $uuddss$ exa-quark. Its QCD binding energy could be large enough to make it (quasi) stable. We show that the cosmological Dark Matter abundance is reproduced thermally if its mass is 1.2 GeV. However, we also find that such mass is excluded by the stability of Oxygen nuclei. Second, we consider the possibility that the instability in the Higgs potential leads to the formation of primordial black holes while avoiding vacuum decay during inflation. We show that the non-minimal Higgs coupling to gravity must be as small as allowed by quantum corrections, $|{\xi }_H|<0.01$. Even so, one must assume that the Universe survived in $e^{120}$ independent regions to fluctuations that lead to vacuum decay with probability 1/2 each.

    hep-phastro-ph.COPRD(2018)·52 citations
11. 11*

    Zooming in on neutrino oscillations with DUNE

    Rahul Srivastava🇪🇸 · Christoph A. Ternes🇪🇸 · Mariam Tórtola🇪🇸 · José W. F. Valle🇪🇸

    We examine the capabilities of the DUNE experiment as a probe of the neutrino mixing paradigm. Taking the current status of neutrino oscillations and the design specifications of DUNE, we determine the experiment's potential to probe the structure of neutrino mixing and CP violation. We focus on the poorly determined parameters ${\theta }_{23}$ and ${\delta }_{CP}$ and consider both two and seven years of run. We take various benchmarks as our true values, such as the current preferred values of ${\theta }_{23}$ and ${\delta }_{CP}$, as well as several theory-motivated choices. We determine quantitatively DUNE's potential to perform a precision measurement of ${\theta }_{23}$, as well as to test the CP violation hypothesis in a model-independent way. We find that, after running for seven years, DUNE will make a substantial step in the precise determination of these parameters, bringing to quantitative test the predictions of various theories of neutrino mixing.

    hep-phhep-exPRD(2018)·27 citations
12. 12*

    $Z$ boson production in bottom-quark fusion: a study of $b$-mass effects beyond leading order

    Stefano Forte🇮🇹 · Davide Napoletano🇫🇷 · Maria Ubiali🇬🇧

    We compute the total cross-section for $Z$ boson production in bottom-quark fusion, applying to this case the method we previously used for Higgs production in bottom fusion. Namely, we match, through the FONLL procedure, the next-to-next-to-leading-log five-flavor scheme result, in which the $b$~quark is treated as a massless parton, with the next-to-leading-order $\text{order}{\alpha }_s^3$ four-flavor scheme computation in which bottom is treated as a massive final-state particle. Our computation provides a test-case for the discussion of issues of scale dependence and treatment of heavy quarks, which we discuss in light of our results.

    hep-phhep-exEPJC(2018)·20 citations
13. 13*

    Slepton Production at e+e- Colliders in the Complex MSSM: A Full One-Loop Analysis

    S. Heinemeyer🇪🇸 · C. Schappacher🇩🇪

    For the search for scalar leptons in the Minimal Supersymmetric Standard Model (MSSM) as well as for future precision analyses of these particles an accurate knowledge of their production and decay properties is mandatory. We evaluate the cross sections for the slepton production at e+e- colliders in the MSSM with complex parameters (cMSSM). The evaluation is based on a full one-loop calculation of the production mechanisms e+e- -> slepton_s slepton_s' including soft and hard photon radiation. The dependence of the slepton production cross sections on the relevant cMSSM parameters is analyzed numerically. We find sizable contributions to many production cross sections. They amount to roughly 15% of the tree-level results but can go up to 40% or higher in extreme cases. Also the complex phase dependence of the one-loop corrections for charged slepton production was found non-negligible. The full one-loop contributions are thus crucial for physics analyses at a future linear e+e- collider such as the ILC or CLIC.

    hep-phEPJC(2018)·13 citations
14. 14*

    A defect action for Wilson loops

    Carlos Hoyos🇪🇸

    An effective action is proposed to compute the expectation value of Wilson loops in $(S)U(N)$ gauge theories. The action consists of fermions localized on the loop and an Abelian gauge field that fixes the representation. The discussion is limited to weak coupling and Wilson loops in the fundamental representation extended along a smooth curve, but there are no restrictions on the matter content as long as the theory has a UV fixed point or it is conformal. For a circular Wilson loop it is found that the expectation value coincides at leading order with the exact result of the $1/2$ BPS Wilson loop of $\mathcal{N}=4$ super Yang-Mills, which is determined by a solvable Gaussian matrix model. This hints towards a universal connection to string theory duals and SYK models.

    ↳ hep-thhep-lathep-phJHEP(2018)·10 citations
15. 15*

    The effective field theory approach of teleparallel gravity, $f(T)$ gravity and beyond

    Chunlong Li🇨🇳 · Yong Cai🇨🇳 · Yi-Fu Cai🇨🇳 · Emmanuel N. Saridakis🇬🇷

    We develop the effective field theory approach to torsional modified gravities, a formalism that allows for the systematic investigation of the background and perturbation levels separately. Starting from the usual effective field theory approach to curvature-based gravity, we suitably generalize it at the background level by including terms of the contracted torsion tensor, and at the perturbation level by including pure torsion perturbative terms and mixed perturbative terms of torsion and curvature. Having constructed the effective field theory action of general torsional modified gravity, amongst others we focus on $f(T)$ gravity and we perform a cosmological application. We investigate the scalar perturbations up to second order, and we derive the expressions of the Newtonian constant and the post Newtonian parameter $\gamma$. Finally, we apply this procedure to two specific and viable $f(T)$ models, namely the power-law and the exponential ones, introducing a new parameter that quantifies the deviation from general relativity and depends on the model parameters. Since this parameter can be expressed in terms of the scalar perturbation mode, a precise measurement of its evolution could be used as an alternative way to impose constraints on $f(T)$ gravity and break possible degeneracies between different $f(T)$ models.

    ↳ gr-qcastro-ph.COhep-phhep-thJCAP(2018)·86 citations
16. 16*

    Hypernatural inflation

    Andrei Linde🇺🇸 · Dong-Gang Wang🇳🇱 · Yvette Welling🇳🇱 · Yusuke Yamada🇺🇸 · Ana Achucarro🇳🇱

    We constructed a model of natural inflation in the context of $\alpha$-attractor supergravity, in which both the dilaton field and the axion field are light during inflation, and the inflaton may be a combination of the two. The T-model version of this theory is defined on the Poincare disk with radius |Z| = 1. It describes a Mexican hat potential with the flat axion direction corresponding to a circle of radius |Z| < 1. The axion decay constant $f_a$ in this theory can be exponentially large because of the hyperbolic geometry of the Poincare disk. Depending on initial conditions, this model may describe $\alpha$-attractor inflation driven by the radial component of the inflaton field, natural inflation driven by the axion field, or a sequence of these two regimes. We also construct the E-model version of this theory, which has similar properties. In addition, we describe generalized $\alpha$-attractor models where the potential can be singular at the boundary of the moduli space, and show that they can provide a simple solution for the problem of initial conditions for the models with plateau potentials.

    ↳ hep-thastro-ph.COgr-qchep-phJCAP(2018)·68 citations
17. 17*

    Covariant Effective Action for Antisymmetric Tensor Field

    Sandeep Aashish🇮🇳 · Sukanta Panda🇮🇳

    Covariant quantization of rank-2 antisymmetric fields is non-trivial due to additional symmetries of the gauge parameters. We present an intuitive way to deal with this additional symmetry of gauge parameters in terms of geometrical understanding of field space. We generalize the DeWitt-Vilkovisky covariant effective action formalism for quantization of such theories. As an application, we quantize a massive rank-2 antisymmetric field using the covariant effective action approach and reproduce previously obtained results.

    ↳ gr-qchep-phhep-thPRD(2018)·10 citations
18. 18*

    Relativistic vortex electrons: paraxial versus non-paraxial regimes

    Dmitry Karlovets🇷🇺

    A plane-wave approximation in particle physics implies that a width of a massive wave packet ${\sigma }_{\perp }$ is much larger than its Compton wavelength ${\lambda }_c=\hslash /mc$. For Gaussian beams or for packets with the non-singular phases (say, the Airy beams), corrections to this approximation are attenuated as ${\lambda }_c^2/{\sigma }_{\perp }^2\ll 1$ and usually negligible. Here we show that this situation drastically changes for particles with the phase vortices associated with an orbital angular momentum $\ell \hslash$. For highly twisted beams with $|\ell |\gg 1$, the non-paraxial corrections get $|\ell |$ times enhanced and $|\ell |$ can already be as large as $10^3$. We describe the relativistic wave packets, both for vortex bosons and fermions, which transform correctly under the Lorentz boosts, are localized in a 3D space, and represent a non-paraxial generalization of the massive Laguerre-Gaussian beams. We compare such states with their paraxial counterpart paying specific attention to the relativistic effects and to the differences from the twisted photons. In particular, a Gouy phase is found to be Lorentz invariant and it generally depends on time rather than on a distance $z$. By calculating the electron packet's mean invariant mass, magnetic moment, etc., we demonstrate that the non-paraxial corrections can already reach the relative values of $10^{-3}$. These states and the non-paraxial effects can be relevant for the proper description of the spin-orbit phenomena in relativistic vortex beams, of scattering of the focused packets by atomic targets, of collision processes in particle and nuclear physics, and so forth.

    ↳ quant-phhep-phphysics.opticsPRA(2018)·36 citations
19. 19*

    A Gribov-Zwanziger type action invariant under background gauge transformations

    Daniel Kroff🇧🇷 · Urko Reinosa🇫🇷

    We propose a Gribov-Zwanziger type action for the Landau-DeWitt gauge that preserves, for any gauge group, the invariance under background gauge transformations. At zero temperature, and to one-loop accuracy, the model can be related to the Gribov no-pole condition. We apply the model to the deconfinement transition in SU(2) and SU(3) Yang-Mills theories and compare the predictions obtained with a single or with various (color dependent) Gribov parameters that can be introduced in the action without jeopardizing its background gauge invariance. The Gribov parameters associated to color directions orthogonal to the background can become negative, while keeping the background effective potential real. In some cases, the proper analysis of the transition requires the potential to be resolved in those regions.

    ↳ hep-thhep-phPRD(2018)·19 citations
20. 20*

    A non-perturbative exploration of the high energy regime in $N_{\text{f}}=3$ QCD

    Mattia Dalla Brida🇮🇹 · Patrick Fritzsch🇨🇭 · Tomasz Korzec🇩🇪 · Alberto Ramos🇮🇪 · Stefan Sint🇮🇪 · Rainer Sommer🇩🇪

    Using continuum extrapolated lattice data we trace a family of running couplings in three-flavour QCD over a large range of scales from about 4 to 128 GeV. The scale is set by the finite space time volume so that recursive finite size techniques can be applied, and Schrödinger functional (SF) boundary conditions enable direct simulations in the chiral limit. Compared to earlier studies we have improved on both statistical and systematic errors. Using the SF coupling to implicitly define a reference scale $1/L_0\approx 4$ GeV through ${\bar{g}}^2(L_0)=2.012$, we quote $L_0{\Lambda }_{\overline{\mathrm{MS}}}^{N_{\mathrm{f}}=3}=0.0791(21)$. This error is dominated by statistics; in particular, the remnant perturbative uncertainty is negligible and very well controlled, by connecting to infinite renormalization scale from different scales $2^n/L_0$ for $n=0,1,\dots ,5$. An intermediate step in this connection may involve any member of a one-parameter family of SF couplings. This provides an excellent opportunity for tests of perturbation theory some of which have been published in a letter [1]. The results indicate that for our target precision of 3 per cent in $L_0{\Lambda }_{\overline{\mathrm{MS}}}^{N_{\mathrm{f}}=3}$, a reliable estimate of the truncation error requires non-perturbative data for a sufficiently large range of values of ${\alpha }_s={\bar{g}}^2/(4\pi )$. In the present work we reach this precision by studying scales that vary by a factor $2^5=32$, reaching down to ${\alpha }_s\approx 0.1$. We here provide the details of our analysis and an extended discussion.

    ↳ hep-lathep-phEPJC(2018)·51 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.