Wed·Oct 31, 2018Wednesday·October 31, 2018

1. 01*

   Automatised matching between two scalar sectors at the one-loop level

   Martin Gabelmann🇩🇪 · Margarete Mühlleitner🇩🇪 · Florian Staub🇩🇪

   Nowadays, one needs to consider seriously the possibility that a large separation between the scale of new physics and the electroweak scale exists. Nevertheless, there are still observables in this scenario, in particular the Higgs mass, which are sensitive to the properties of the UV theory. In order to obtain reliable predictions for a model which involves very heavy degrees of freedom, the precise matching to an effective theory is necessary. While this has been so far only studied for a few selected examples, we present an extension of the $\mathtt{Mathematica}$ package $\mathtt{SARAH}$ to perform automatically the matching between two scalar sectors at the full one-loop level for general models. We show that we can reproduce all important results for commonly studied models like split- or high-scale supersymmetry. One can now easily go beyond that and study new ideas involving very heavy states, where the effective model can either be just the standard model or an extension of it. Also scenarios with several matching scales can be easily considered. We provide model files for the MSSM with seven different mass hierarchies as well as two high-scale versions of the NMSSM. Moreover, it is explained how new models are implemented.

   hep-phEPJC(2019)·23 citations
2. 02*

   Dissection of an SO(5) x U(1) Gauge-Higgs Unification Model

   Jongmin Yoon🇺🇸 · Michael E. Peskin🇺🇸

   We analyze models of electroweak symmetry breaking in warped 5-dimensional space with gauge bosons and fermions in the bulk. The Higgs boson is identified with the 5th component of a gauge field. We dynamically generate the Higgs potential using a competition between the top quark multiplet and another fermion multiplet to create a little hierarchy characterized by a small parameter s = v/f. Using a Green's function method, we compute the properties of the model systematically as a power series in s. We discuss the constraints on this model from the measured value of the Higgs mass, the masses of top quark partners, and precision electroweak observables.

   hep-phPRD(2019)·24 citations
3. 03*

   Production of $t\bar{t}$ pairs via $\gamma \gamma$ fusion with photon transverse momenta and proton dissociation

   Marta Łuszczak🇵🇱 · Laurent Forthomme🇫🇮 · Wolfgang Schäfer🇵🇱 · Antoni Szczurek🇵🇱

   We discuss the production of $t\bar{t}$ quark-antiquark pairs in proton-proton collisions via the $\gamma \gamma$ fusion mechanism. We include topologies in which both protons stay intact or one or even both of them undergo dissociation. The calculations are performed within the $k_{\mathrm{T}}$-factorisation approach, including transverse momenta of intermediate photons. Photon fluxes associated to inelastic (dissociative) processes are calculated based on modern parameterisations of proton structure functions. We find an integrated cross section of about 2.36 fb at $\sqrt{s}=$ 13 TeV for all contributions. The cross section for the fully elastic process is the smallest. Inelastic contributions are significantly reduced when a veto on outgoing jets is imposed. We present several differential distributions in rapidity and transverse momenta of single $t$ or $\bar{t}$ quarks/antiquarks as well as distributions in invariant mass of both the $t\bar{t}$ and masses of dissociated systems. A few two-dimensional distributions are presented in addition.

   hep-phJHEP(2019)·24 citations
4. 04*

   Electroweak superpartners scrutinized at the LHC in events with multi-leptons

   Inaki Lara🇪🇸 · Daniel E. Lopez-Fogliani🇦🇷 · Carlos Munoz🇪🇸

   We analyze a multi-lepton signal plus missing transverse energy from neutrinos expected at the LHC for a Bino-like neutralino as the lightest supersymmetric particle (LSP), when the left sneutrino is the next-to-LSP and hence a suitable source of Binos. The discussion is carried out in the framework of the $\mu \nu$SSM, where the presence of $R$-parity violating (RPV) couplings involving right-handed neutrinos solves the $\mu$ problem and can reproduce simultaneously the neutrino data. Left sneutrinos/sleptons are pair produced at $pp$ collisions decaying to Binos, with the latter decaying via RPV to $W\ell$ or $Z\nu$. This signal can be compared with LHC searches for electroweak superpartners through chargino-neutralino production. The reduced cross section of the sneutrino/slepton production in comparison with the one of the latter process, limits the sensitivity of the searches to small sneutrino/slepton masses. Although the resulting compressed spectrum typically evades the aforementioned searches, we show that analyses using recursive jigsaw reconstruction are sensitive to these scenarios. As a by-product, we find that the region of Bino masses $110-120$ GeV and sneutrino masses $120-140$ GeV can give rise to a tri-lepton signal compatible with the local excess recently reported by ATLAS.

   hep-phhep-exPLB(2019)·21 citations
5. 05*

   Low-scale leptogenesis with three heavy neutrinos

   Asmaa Abada🇫🇷 · Giorgio Arcadi🇩🇪 · Valerie Domcke🇩🇪 · Marco Drewes🇧🇪 · Juraj Klaric🇩🇪 · Michele Lucente🇧🇪

   Leptogenesis induced by the oscillations of GeV-scale neutrinos provides a minimal and testable explanation of the baryon asymmetry of the Universe. In this work we extend previous studies invoking only two heavy neutrinos to the case of three heavy neutrinos. We find qualitatively new behaviour as a result of lepton number violating oscillations and decays, strong flavour effects in the washout and a resonant enhancement due to matter effects. An approximate global $B-\bar{L}$ symmetry (representing the difference of baryon and a generalised lepton number) can protect the light neutrino masses from large radiative corrections, while simultaneously providing the ingredients for the resonant enhancement of the lepton asymmetry due to thermal contributions to the heavy neutrino dispersion relations. This mechanism is particularly efficient for large heavy neutrino mixing angles near the current experimental limits, a regime in which leptogenesis is not feasible in the minimal scenario with two heavy neutrinos. In this new parameter regime, low-scale leptogenesis is testable by the LHC and other existing experiments.

   hep-phhep-exJHEP(2019)·103 citations
6. 06*

   Top-bottom-tau Yukawa coupling unification in the MSSM+1VF and fermion masses as IR fixed points

   Radovan Dermisek🇺🇸 · Navin McGinnis🇺🇸

   In the MSSM extended by a complete vectorlike family, precise top, bottom and tau Yukawa coupling unification can be achieved assuming SUSY threshold corrections which are typical for comparable superpartner masses. Furthermore, the unification is possible with a large unified coupling, implying that all three fermion masses can be simultaneously close to their IR fixed points. Assuming unified Yukawa couplings of order one or larger, the preferred common scale of new physics (superpartners and vectorlike matter) is in the 3 TeV to 30 TeV range, with larger couplings favoring smaller scales. Splitting superpartner masses from masses of vectorlike fields, the preferred scales extend in both directions. The multi-TeV scale for superpartners is compatible with and independently suggested by the Higgs boson mass.

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

   Study of the quasi-two-body decays B^{0}_{s} \rightarrow \psi(3770)(\psi(3686))\pi^+\pi^- with perturbative QCD approach

   Ze-Rui Liang🇨🇳 · Feng-Bo Duan🇨🇳 · Xian-Qiao Yu🇨🇳

   In this note, we study the contributions from the S-wave resonances, f_{0}(980) and f_{0}(1500), to the B^{0}_{s}\rightarrow \psi(3770)\pi^ {+}\pi^{-} decay by introducing the S-wave \pi\pi distribution amplitudes within the framework of the perturbative QCD approach. Both resonant and nonresonant contributions are contained in the scalar form factor in the S-wave distribution amplitude \Phi^S_{\pi\pi}. Since the vector charmonium meson \psi(3770) is a S-D wave mixed state, we calculated the branching ratios of S-wave and D-wave respectively, and the results indicate that f_{0}(980) is the main contribution of the considered decay, and the branching ratio of the \psi(2S) mode is in good agreement with the experimental data. We also take the S-D mixed effect into the B^{0}_{s}\rightarrow \psi(3686)\pi^ {+}\pi^{-} decay. Our calculations show that the branching ratio of B^{0}_{s}\rightarrow \psi(3770)(\psi(3686))\pi^ {+}\pi^{-} can be at the order of 10^{-5}, which can be tested by the running LHC-b experiments.

   hep-phEPJC(2019)·4 citations
8. 08*

   Chiral phase transition and QCD phase diagram from AdS/QCD

   Zhen Fang🇨🇳 · Yue-Liang Wu🇨🇳 · Lin Zhang🇨🇳

   We study the chemical potential effects on the chiral phase transition in a simply improved soft-wall AdS/QCD model, which can realize consistently the properties of linear confinement and spontaneous chiral symmetry breaking. The $\mu -T$ phase diagrams with both zero and physical quark masses have been obtained from this model. For the case of physical quark mass, the chiral transition has a crossover behavior at low chemical potential. With the increase of the chemical potential $\mu$, the critical temperature $T_c$ descends towards zero, and the crossover transition turns into a first-order one at some intermediate value of $\mu$, which implies that a critical end point naturally exists in this improved soft-wall model. All these features agree with our current perspective on the QCD phase diagram.

   hep-phPRD(2019)·32 citations
9. 09*

   Electrical conductivity and relaxation via colored noise in a hadronic gas

   Jan Hammelmann🇩🇪 · Juan M. Torres-Rincon🇺🇸 · Jean-Bernard Rose🇩🇪 · Moritz Greif🇩🇪 · Hannah Elfner🇩🇪

   Motivated by the theory of relativistic hydrodynamic fluctuations we make use of the Green-Kubo formula to compute the electrical conductivity and the (second-order) relaxation time of the electric current of an interacting hadron gas. We use the recently developed transport code SMASH to numerically solve the coupled set of Boltzmann equations implementing realistic hadronic interactions. In particular, we explore the role of the resonance lifetimes in the determination of the electrical relaxation time. As opposed to a previous calculation of the shear viscosity we observe that the presence of resonances with lifetimes of the order of the mean-free time does not appreciably affect the relaxation of the electric current fluctuations. We compare our results to other approaches describing similar systems, and provide the value of the electrical conductivity and the relaxation time for a hadron gas at temperatures between T=60 MeV and T=150 MeV.

   hep-phnucl-thPRD(2019)·29 citations
10. 10*

    Strong Isospin Breaking in the Decay Constants of Heavy-Light Mesons from Local-Duality QCD Sum Rules

    Wolfgang Lucha🇦🇹 · Dmitri Melikhov🇦🇹 · Silvano Simula🇮🇹

    We explore, by a rather peculiar limit of QCD sum rules subject to a Borel transformation (realized by allowing the related Borel mass parameter to approach infinity), how the small difference of the masses of up and down quark translates into the leptonic decay constants of pseudoscalar or vector heavy-light mesons. For the charmed and bottom mesons, we find that the decay constants of their lowest-lying charged and neutral representatives should differ by an amount of the order of 1 MeV.

    hep-phhep-latnucl-thPoS(2018)·1 citation
11. 11*

    Collider Searches for Long-Lived Particles Beyond the Standard Model

    Lawrence Lee🇺🇸 · Christian Ohm🇸🇪 · Abner Soffer🇮🇱 · Tien-Tien Yu🇺🇸

    Experimental tests of the Standard Model of particle physics (SM) find excellent agreement with its predictions. Since the original formation of the SM, experiments have provided little guidance regarding the explanations of phenomena outside the SM, such as the baryon asymmetry and dark matter. Nor have we understood the aesthetic and theoretical problems of the SM, despite years of searching for physics beyond the Standard Model (BSM) at particle colliders. Some BSM particles can be produced at colliders yet evade being discovered, if the reconstruction and analysis procedures not matched to characteristics of the particle. An example is particles with large lifetimes. As interest in searches for such long-lived particles (LLPs) grows rapidly, a review of the topic is presented in this article. The broad range of theoretical motivations for LLPs and the experimental strategies and methods employed to search for them are described. Results from decades of LLP searches are reviewed, as are opportunities for the next generation of searches at both existing and future experiments.

    hep-phhep-exPPNP(2019)·249 citations
12. 12*

    The Effect of the Earth Matter on Three Neutrino Oscillations and Sensitivity to CP Phase Parameter

    Bushra Shafaq🇵🇰 · Faisal Akram🇵🇰

    We find an analytical expression of neutrino evolution operator in the Earth matter using perturbative approach in the context of three neutrino oscillations. We find that our analytical expression is highly accurate by comparing its results with the numerical solutions of neutrino evolution equation at energy scales relevant for solar, reactor, atmospheric, and accelerator neutrinos. Using our analytical approach we study the accuracy of hypothesis of treating the Earth density piecewise constant. We also study how the Earth matter effect can change the sensitivity to CP phase parameter ${\delta }_{CP}$. Through nadir angle averaged conversion probabilities of neutrino and anti-neutrino, we find that the sensitivity to ${\delta }_{CP}$ is maximum in the energy range 0.2 to 1 GeV and through energy averaged conversion probabilities, we find that the sensitivity is maximum about nadir angle $72.5^{\text{o}}$ for neutrinos oscillating in the Earth matter.

    hep-phEur.Phys.J.Plus(2020)·2 citations
13. 13*

    A minimal model of inflation and dark radiation

    Kristjan Kannike🇪🇪 · Aleksei Kubarski🇪🇪 · Luca Marzola🇪🇪 · Antonio Racioppi🇪🇪

    We show that a minimal extension of the Standard Model including a new complex scalar field can explain inflation and the observed effective number of neutrinos. The real part of the singlet plays the role of the inflaton field, while the Goldstone boson emerging from the spontaneous symmetry breaking of a global $U(1)$ symmetry contributes to dark radiation and increases the effective number of neutrino species by $0.3$ over the Standard Model value. After detailing the phenomenology of the model, we find that the predicted inflationary observables are in agreement with the current bounds, once the dark radiation component is allowed, both within the metric and Palatini formulation of non-minimally coupled gravity.

    hep-phastro-ph.COPLB(2019)·33 citations
14. 14*

    A study of the vector meson $\psi (4040)$

    Milena Piotrowska🇵🇱 · Francesco Giacosa🇵🇱

    We investigate the well-known $c\bar{c}$ vector state $\psi (4040)$ in the framework of a quantum field theoretical model. In particular, we study its spectral function and search for the pole(s) in the complex plane. Quite interestingly, the spectral function has a non-standard shape and two poles are present. The role of the meson-meson quantum loops (in particular $D{D}^{\ast }$ ones) is crucial and could also explain the not yet confirmed state $Y(4008)$.

    hep-phEPJ Web Conf.(2019)·2 citations
15. 15*

    Acceleration of a proton along a uniform magnetic field: Casimir momentum of leptons

    Manuel Donaire🇪🇸

    It is commonly assumed that a charged particle does not accelerate linearly along a spatially uniform magnetic field. We show that this is no longer the case if the interaction of the particle with the quantum vacuum is chiral, in which case parity and time-reversal symmetries are simultaneously broken. In particular, this is the situation of an electroweak interacting particle in the presence of a uniform magnetic field. We demonstrate first that, in a spatially uniform and adiabatically time-varying magnetic field, a proton coupled to the leptonic vacuum acquires a kinetic momentum antiparallel to the magnetic field, whereas virtual leptons gain an equivalent Casimir momentum in the opposite direction. Remarkably, leptons remain virtual throughout the process, which means that the proton acceleration is not caused by the recoil associated to the emission of any actual particle. The kinetic energy of the proton is part of its electroweak self-energy, which is provided by the source of magnetic field. In addition we find that, in a constant and uniform magnetic field, the adiabatic spin-relaxation of a single proton is accompanied by its acceleration along the magnetic field. We estimate that, at the end of the spin-polarization process, the proton reaches a velocity of the order of $\mu$m/s. The latter finding may lie within the scope of experimental observations.

    hep-ph0 citations
16. 16*

    Naturalness, the Hyperbolic Branch and Prospects for the Observation of Charged Higgs at High Luminosity LHC and 27 TeV LHC

    Amin Aboubrahim🇺🇸 · Pran Nath🇺🇸

    One of the early criterion proposed for naturalness was a relatively small Higgs mixing parameter $\mu$ with $\mu /M_Z$ order few. A relatively small $\mu$ may lead to heavier Higgs masses ($H^0,A,H^{\pm }$ in MSSM) which are significantly lighter than other scalars such as squarks. Such a situation is realized on the hyperbolic branch of radiative breaking of the electroweak symmetry. In this analysis we construct supergravity unified models with relatively small $\mu$ in the sense described above and discuss the search for the charged Higgs boson $H^{\pm }$ at HL-LHC and HE-LHC where we also carry out a relative comparison of the discovery potential of the two using the decay channel $H^{\pm }\to \tau \nu$. It is shown that an analysis based on the traditional linear cuts on signals and backgrounds is not very successful in extracting the signal while, in contrast, machine learning techniques such as boosted decision trees prove to be far more effective. Thus it is shown that models not discoverable with the conventional cut analyses become discoverable with machine learning techniques. Using boosted decision trees we consider several benchmarks and analyze the potential for their $5\sigma$ discovery at the 14 TeV HL-LHC and at 27 TeV HE-LHC. It is shown that while the ten benchmarks considered with the charged Higgs boson mass in the range 373 GeV- 812 GeV are all discoverable at HE-LHC, only four of the ten with Higgs boson masses in the range 373 GeV-470 GeV are discoverable at HL-LHC. Further, while the model points discoverable at both HE-LHC and HL-LHC would require up to 7 years of running time at HL-LHC, they could all be discovered in a period of few months at HE-LHC.

    hep-phhep-exPRD(2018)·20 citations
17. 17*

    Global description of bottomonium suppression in proton-nucleus and nucleus-nucleus collisions at LHC energies

    Elena G. Ferreiro🇪🇸

    We show that we can reach a global and coherent description of bottomonium suppression in both proton-nucleus and nucleus-nucleus collisions at the LHC energies. The measured relative suppression of the excited bottomonium states as compared to their ground state allows us to constrain the scattering cross sections between the bottomonia and the comovers created during the collisions. Our result hints at a similar energy distribution of these comovers in the environment created by proton-nucleus and nucleus-nucleus collisions. Along the way of our study, we also update our knowledge for the bottomonium feed-down pattern and our comprehension on the modification of the nuclear parton distribution functions in proton-nucleus collisions. We present our results for $p$Pb collisions at 5.02 and 8.16 TeV and for PbPb collisions at 2.76 and 5.02 TeV.

    hep-phnucl-thPoS(2018)·5 citations
18. 18*

    Jet Veto Resummation with Jet Rapidity Cuts

    Johannes K. L. Michel🇩🇪 · Piotr Pietrulewicz🇩🇪 · Frank J. Tackmann🇩🇪

    Jet vetoes are widely used in experimental analyses at the LHC to distinguish different hard-interaction processes. Experimental jet selections require a cut on the (pseudo)rapidity of reconstructed jets, $|{\eta }_{\mathrm{jet}}|\le {\eta }_{\mathrm{cut}}$. We extend the standard jet-$p_T$ (jet-veto) resummation, which implicitly works in the limit ${\eta }_{\mathrm{cut}}\to \infty$, by incorporating a finite jet rapidity cut. We also consider the case of a step in the required $p_T^{\mathrm{cut}}$ at an intermediate value of $|\eta |\simeq 2.5$, which is of experimental relevance to avoid the increased pile-up contamination beyond the reach of the tracking detectors. We identify all relevant parametric regimes, discuss their factorization and resummation as well as the relations between them, and show that the phenomenologically relevant regimes are free of large nonglobal logarithms. The ${\eta }_{\mathrm{cut}}$ dependence of all resummation ingredients is computed to the same order to which they are currently known for ${\eta }_{\mathrm{cut}}\to \infty$. Our results pave the way for carrying out the jet-veto resummation including a sharp cut or a step at ${\eta }_{\mathrm{cut}}$ to the same order as is currently available in the ${\eta }_{\mathrm{cut}}\to \infty$ limit. The numerical impact of the jet rapidity cut is illustrated for benchmark $q\bar{q}$ and $gg$ initiated color-singlet processes at NLL${}^{\prime }+$NLO. We find that a rapidity cut at high ${\eta }_{\mathrm{cut}}=4.5$ is safe to use and has little effect on the cross section. A sharp cut at ${\eta }_{\mathrm{cut}}=2.5$ can in some cases lead to a substantial increase in the perturbative uncertainties, which can be mitigated by instead using a step in the veto.

    hep-phJHEP(2019)·40 citations
19. 19*

    Phenomenology with a recoil-free jet axis: TMD fragmentation and the jet shape

    Duff Neill🇺🇸 · Andreas Papaefstathiou🇳🇱 · Wouter J. Waalewijn🇳🇱 · Lorenzo Zoppi🇳🇱

    We study the phenomenology of recoil-free jet axes using analytic calculations and Monte Carlo simulations. Our focus is on the average energy as function of the angle with the jet axis (the jet shape), and the energy and transverse momenta of hadrons in a jet (TMD fragmentation). We find that the dependence on the angle (or transverse momentum) is governed by a power law, in contrast to the double-logarithmic dependence for the standard jet axis. The effects of the jet radius, jet algorithm, angular resolution and grooming are investigated. TMD fragmentation is important for constraining the structure of the proton through semi-inclusive deep-inelastic scattering. These observables are also of interest to the LHC, for example to constrain ${\alpha }_s$ from precision jet measurements, or probe the quark-gluon plasma in heavy-ion collisions.

    hep-phhep-exJHEP(2019)·30 citations
20. 20*

    Right-handed Neutrino Dark Matter with Radiative Neutrino Mass in Gauged $B-L$ Model

    Debasish Borah🇮🇳 · Dibyendu Nanda🇮🇳 · Nimmala Narendra🇮🇳 · Narendra Sahu🇮🇳

    We study the possibility of right-handed neutrino dark matter (DM) in gauged $U(1{)}_{B-L}\times Z_2$ extension of the standard model augmented by an additional scalar doublet, being odd under the $Z_2$ symmetry, to give rise the scotogenic scenario of radiative neutrino masses. Due to lepton portal interactions, the right-handed neutrino DM can have additional co-annihilation channels apart from the usual annihilations through $Z_{B-L}$ which give rise to much more allowed mass of DM from relic abundance criteria, even away from the resonance region like $M_{\mathrm{DM}}\approx M_{Z_{B-L}}/2$. This enlarged parameter space is found to be consistent with neutrino mass constraints while being sensitive to direct detection experiments of DM as well as rare decay experiments looking for charged lepton flavour violating decays like $\mu \to e\gamma$. Due to the possibility of the $Z_2$ odd scalar doublet being the next to lightest stable particle that can be sufficiently produced in colliders by virtue of its gauge interactions, one can have interesting signatures like displaced vertex or disappearing charged tracks provided that the mass splitting $\delta M$ between DM and the next to lightest stable particle (NLSP) is small. In particular, if $\delta M<m_{\tau }=1.77$ GeV, then we get large displaced vertex signature of NLSP while being consistent with neutrino mass, lepton flavour violation and observed relic density.

    hep-phastro-ph.CONPB(2020)·38 citations
21. 21*

    Numerical calculation of the full two-loop electroweak corrections to muon (g-2)

    Tadashi Ishikawa (1)🇯🇵 · Nobuya Nakazawa (2)🇯🇵 · Yoshiaki Yasui (3) ((1) High Energy Accelerator Organization (KEK), (2) Kogakuin University, (3) Tokyo Management College)🇯🇵

    Numerical calculation of two-loop electroweak corrections to the muon anomalous magnetic moment ($g$-2) is done based on, on shell renormalization scheme (OS) and free quark model (FQM). The GRACE-FORM system is used to generate Feynman diagrams and corresponding amplitudes. Total 1780 two-loop diagrams and 70 one-loop diagrams composed of counter terms are calculated to get the renormalized quantity. As for the numerical calculation, we adopt trapezoidal rule with Double Exponential method (DE). Linear extrapolation method (LE) is introduced to regularize UV- and IR-divergences and to get finite values. The reliability of our result is guaranteed by several conditions. The sum of one and two loop electroweak corrections in this renormalization scheme becomes $a_{\mu }^{EW:OS}[1+2-\mathrm{loop}]=151.2(\pm 1.0)\times 10^{-11}$, where the error is due to the numerical integration and the uncertainty of input mass parameters and of the hadronic corrections to electroweak loops. By taking the hadronic corrections into account, we get $a_{\mu }^{EW}[1+2-\mathrm{loop}]=152.9(\pm 1.0)\times 10^{-11}$. It is in agreement with the previous works given in PDG within errors.

    hep-phPRD(2019)·27 citations
22. 22*

    A Graceful Exit for the Cosmological Constant Damping Scenario

    Oleg Evnin🇹🇭 · Kévin Nguyen🇧🇪

    We present a broad and simple class of scalar-tensor scenarios that successfully realize dynamical damping of the effective cosmological constant, therefore providing a viable dynamical solution to the fine-tuning or "old" cosmological constant problem. In contrast to early versions of this approach, pioneered in the works of A. Dolgov in the 1980es, these do not suffer from unacceptable variations of Newton's constant, as one aims at a small but strictly positive (rather than zero) late-time curvature. In our approach, the original fine-tuning issue is traded for a hierarchy of couplings, and we further suggest a way to naturally generate this hierarchy based on fermion condensation and softly broken field shift symmetry.

    ↳ gr-qchep-phhep-thPRD(2018)·18 citations
23. 23*

    Breaking the Fluctuation-Dissipation Relation by Universal Transport Processes

    A. Piñeiro Orioli🇺🇸 · J. Berges🇩🇪

    Universal phenomena far from equilibrium exhibit additional independent scaling exponents and functions as compared to thermal universal behavior. For the example of an ultracold Bose gas we simulate nonequilibrium transport processes in a universal scaling regime and show how they lead to the breaking of the fluctuation-dissipation relation. As a consequence, the scaling of spectral functions (commutators) and statistical correlations (anticommutators) between different points in time and space become linearly independent with distinct dynamic scaling exponents. As a macroscopic signature of this phenomenon we identify a transport peak in the statistical two-point correlator, which is absent in the spectral function showing the quasiparticle peaks of the Bose gas.

    ↳ cond-mat.quant-gascond-mat.stat-mechhep-phquant-phPRL(2019)·34 citations
24. 24*

    Swimming and swirling colorful ghosts

    Giorgio Torrieri🇧🇷

    We show that the ideal fluid limit, defined as the existance of a flow frame $u_{\mu }$ with respect to which the fluid is homogeneus and isotropic, and the consequent independence of the equation of state on $u_{\mu }$, is incompatible with non-Abelian gauge theory. Instead, the equation of state becomes dependent on $u_{\mu }$ via modes which are roughly equivalent to ghost modes in the hydrodynamic limit. These modes can be physically imagined as a field of 'purcell swimmers' whose 'arms and legs' are outstretched in Gauge space. Also, vorticity should couple to the Wilson loop via the chromo-electro-magnetic field tensor, which in this limit is not a 'force' but instead represents the polarization tensor of the gluons. We show that because of this coupling vorticity also aquires swirling non-hydrodynamic modes. We then argue that these swirling and swimming non-hydodynamic modes are the manifestation of gauge redunancy within local equilibrium, and speculate on their role in quark-gluon plasma thermalization

    ↳ hep-thhep-phnucl-thphysics.flu-dynEPJA(2020)·9 citations
25. 25*

    Topological couplings in higher derivative extensions of supersymmetric three-form gauge theories

    Muneto Nitta🇯🇵 · Ryo Yokokura🇯🇵

    We consider a topological coupling between a pseudo-scalar field and a 3-form gauge field in $\mathcal{N}=1$ supersymmetric higher derivative 3-form gauge theories in four spacetime dimensions. We show that ghost/tachyon-free higher derivative Lagrangians with the topological coupling can generate various potentials for the pseudo-scalar field by solving the equation of motion for the 3-form gauge field. We give two examples of higher derivative Lagrangians and the corresponding potentials: one is a quartic order term of the field strength and the other is the term which can generate a cosine-type potential of the pseudo-scalar field.

    ↳ hep-thhep-phJHEP(2019)·15 citations
26. 26*

    Search for neutron-hidden neutron interbrane transitions with MURMUR, a low-noise neutron passing-through-walls experiment

    Coraline Stasser🇧🇪 · Michaël Sarrazin🇫🇷 · Guy Terwagne🇧🇪

    Multi-braneworld universe is at the heart of many scenarios of physics beyond the Standard Model and the cosmological model $\Lambda CDM$. It is thus an important concern to constrain these scenarios which also allow for experiments below the GeV scale. MURMUR is a new neutron-passing-through-walls experiment designed to constrain neutron-hidden neutron transitions in the context of braneworlds scenarios. As our visible universe could be a 3-brane embedded in a multidimensional bulk, adjacent hidden 3-branes are often expected. Their existence can be constrained as matter exchange between braneworlds must occur with a swapping probability $p$. A neutron $n$ can convert into a hidden neutron $n^{\prime }$ when scattered by a nucleus with cross section $\sigma (n\to n^{\prime })$ $\propto$ ${\sigma }_E(n\to n)p$, where ${\sigma }_E$ is the usual elastic cross-section. Hidden neutrons could therefore be generated in the moderator medium of a nuclear reactor, where high-flux neutrons undergo many elastic collisions. All the theoretical and technological keys of this experiment soon to be installed at the nuclear research reactor BR2 (SCK.CEN, Mol, Belgium) are introduced.

    ↳ nucl-exhep-exhep-phphysics.ins-detEPJ Web Conf.(2019)·2 citations
27. 27*

    Bootstrapping QCD: the Lake, the Peninsula and the Kink

    Andrea L. Guerrieri🇧🇷 · Joao Penedones🇨🇭 · Pedro Vieira🇧🇷

    We consider the S-matrix bootstrap of four dimensional scattering amplitudes with $O(3)$ symmetry and no bound-states. We explore the allowed space of scattering lengths which parametrize the interaction strength at threshold of the various scattering channels. Next we consider an application of this formalism to pion physics. A signature of pions is that they are derivatively coupled leading to (chiral) zeros in their scattering amplitudes. In this work we explore the multi-dimensional space of chiral zeros positions, scattering length values and resonance mass values. Interestingly, we encounter lakes, peninsulas and kinks depending on which sections of this intricate multi-dimensional space we consider. We discuss the remarkable location where QCD seems to lie in these plots, based on various experimental and theoretical expectations.

    ↳ hep-thhep-phPRL(2019)·111 citations
28. 28*

    Regressive and generative neural networks for scalar field theory

    Kai Zhou🇩🇪 · Gergely Endrődi🇩🇪 · Long-Gang Pang🇺🇸 · Horst Stöcker🇩🇪

    We explore the perspectives of machine learning techniques in the context of quantum field theories. In particular, we discuss two-dimensional complex scalar field theory at nonzero temperature and chemical potential -- a theory with a nontrivial phase diagram. A neural network is successfully trained to recognize the different phases of this system and to predict the value of various observables, based on the field configurations. We analyze a broad range of chemical potentials and find that the network is robust and able to recognize patterns far away from the point where it was trained. Aside from the regressive analysis, which belongs to supervised learning, an unsupervised generative network is proposed to produce new quantum field configurations that follow a specific distribution. An implicit local constraint fulfilled by the physical configurations was found to be automatically captured by our generative model. We elaborate on potential uses of such a generative approach for sampling outside the training region.

    ↳ hep-lathep-phphysics.data-anPRD(2019)·109 citations
29. 29*

    Nonminimal Coleman--Weinberg Inflation with an $R^2$ term

    Alexandros Karam🇬🇷 · Thomas Pappas🇬🇷 · Kyriakos Tamvakis🇬🇷

    We extend the Coleman--Weinberg inflationary model where a scalar field $\varphi$ is non-minimally coupled to gravity with the addition of the $R^2$ term. We express the theory in terms of two scalar fields and going to the Einstein frame we employ the Gildener--Weinberg formalism, compute the one-loop effective potential and essentially reduce the problem to the case of single-field inflation. It turns out that there is only one free parameter, namely, the mixing angle between the scalars. For a wide range of this angle, we compute the inflationary observables which are in agreement with the latest experimental bounds. The effect of the $R^2$ term is that it lowers the value of the tensor-to-scalar ratio $r$.

    ↳ gr-qcastro-ph.COhep-phhep-thJCAP(2019)·72 citations
30. 30*

    NA61/SHINE experiment - programme beyond 2020

    Ludwik Turko🇵🇱

    The fixed-target NA61/SHINE experiment (SPS CERN) looks for the critical point (CR) of strongly interacting matter and the properties of the onset of deconfinement. It is a scan of measurements of particle spectra and fluctuations in proton-proton, proton-nucleus and nucleus-nucleus interactions as a function of collision energy and system size, corresponding to a two dimensional phase diagram (T-${\mu }_B$). New measurements and their objectives, related to the third stage of the experiment after 2020 are presented and discussed here.

    ↳ nucl-exhep-phParticles(2018)·2 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.