Fri·Dec 6, 2019Friday·December 6, 2019

1. 01*

   Heavy Quarkonium in Extreme Conditions

   Alexander Rothkopf🇳🇴

   In this report we review recent progress achieved in the understanding of heavy quarkonium under extreme conditions from a theory perspective. Its focus lies both on quarkonium properties in thermal equilibrium, as well as recent developments towards a genuine real-time description, valid also out-of-equilibrium. We will give an overview of the theory tools developed and deployed over the last decade, including effective field theories, lattice field theory simulations, modern methods for spectral reconstructions and the the open-quantum systems paradigm. The report will discuss in detail the concept of quarkonium melting, providing the reader with a contemporary perspective. In order to judge where future progress is needed we will also discuss recent results from experiments and phenomenological modeling of quarkonium in relativistic heavy-ion collisions.

   hep-phhep-latnucl-thPhys.Rept.(2020)·254 citations
2. 02*

   Charged scalar production at the Compact Linear Collider for the $S_3\otimes {\mathbb{Z}}_2$ model

   G. De Conto🇧🇷 · A. C. B. Machado🇧🇷 · J. Montaño🇲🇽 · P. Chimenti🇧🇷

   We present a model with $S_3\otimes {\mathbb{Z}}_2$ model plus a sterile neutrino and its phenomenological expectations for the production of charged scalars at the Compact Linear Collider. At tree level, our model predicts a total cross section in between 0.1 and $10^{-5}$ pb for the $e^{-}{e}^{+}\to H^{+}{H}^{-}$ process, considering all possible mass values for the charged scalar in the CLIC experiment. We also show that this prediction holds regardless of the masses of the other exotic particles and their couplings.

   hep-phhep-thEPJC(2020)·0 citations
3. 03*

   Exploring hybrid equation of state with constraints from tidal deformability of GW170817

   Qing-wu Wang🇨🇳 · Chao Shi🇨🇳 · Yan Yan🇨🇳 · Hong-Shi Zong🇨🇳

   With a interpolation method on the P-$\mu$ plane, a hybrid equation of state is explored. The quark phase is described by our newly developed self-consistent two-flavor Nambu$-$Jona-Lasinio model. It retains the contribution from the vector channel in the Fierz-transformed Lagrangian by introducing a weighting parameter $\alpha$ [Chin. Phys. C \textbf{43}, 084102 (2019)]. In the hadron phase we use the relativistic mean-field theory. We study the dependence of hybrid EOS and mass-radius relation on $\alpha$. It is found that increasing $\alpha$ makes the hybrid EOS softer in the medium pressure. We can get stellar mass larger than $2M_{\odot }$. Further, we calculate the tidal deformability $\tilde{\Lambda }$ for binary stars and compare with recent analysis GW170817 [Phys. Rev. X \textbf{9}, 011001 (2019)].

   hep-phnucl-thNPA(2022)·17 citations
4. 04*

   Renormalization schemes for mixing angles in extended Higgs sectors

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

   The proper renormalization of mixing angles in quantum field theories is a long-standing problem. It is relevant for the renormalization of the quark mixing matrix in the Standard Model and for various mixing scenarios in theories beyond. In this contribution we specifically consider theories with extended scalar sectors. We describe renormalization schemes for mixing angles based on combinations of observables or symmetry requirements such as rigid or background-field gauge invariance and compare their properties to previous approaches such as $\overline{MS}$ schemes. We formulate specific renormalization conditions for the mixing angles in the Two-Higgs-Doublet Model and the Higgs-Singlet Extension of the Standard Model and calculate electroweak corrections to Higgs-boson decays via W- or Z-boson pairs within these models for a selection of (new and old) renormalization schemes.

   hep-ph4 citations
5. 05*

   Interference between the Atmospheric and Solar Oscillation Amplitudes

   Patrick Huber🇺🇸 · Hisakazu Minakata🇺🇸 · Rebekah Pestes🇺🇸

   We propose to detect the interference effect between the atmospheric-scale and solar-scale waves of neutrino oscillation, one of the key consequences of the three-generation structure of leptons. In vacuum, we show that there is a natural and general way of decomposing the oscillation amplitude into these two oscillation modes. The nature of the interference is cleanest in the ${\bar{\nu }}_e$ disappearance channel since it is free from the CP-phase $\delta$. We find that the upcoming JUNO experiment offers an ideal setting to observe this interference with more than $4\sigma$ significance, even under conservative assumptions about the systematic uncertainties.

   hep-phPRD(2020)·8 citations
6. 06*

   Resampling Algorithms for High Energy Physics Simulations

   Jimmy Olsson🇸🇪 · Simon Plätzer🇦🇹 · Malin Sjodahl🇸🇪

   We demonstrate that the method of interleaved resampling in the context of parton showers can tremendously improve the statistical convergence of weighted parton shower evolution algorithms. We illustrate this by several examples showing significant statistical improvement.

   hep-phphysics.comp-phEPJC(2020)·8 citations
7. 07*

   ${\text{TM}}_1$ neutrino mixing with $\sin {\theta }_{13}=\frac{1}{\sqrt{3}}\sin \frac{\pi }{12}$

   R Krishnan🇮🇳

   We construct a neutrino model using the flavour group $S_4\times C_4\times C_3\times C_2$ under the type-1 seesaw mechanism. The vacuum alignments of the flavons in the model lead to ${\text{TM}}_1$ mixing with $\sin {\theta }_{13}=\frac{1}{\sqrt{3}}\sin \frac{\pi }{12}$. The mixing also exhibits $\mu \text{-}\tau$ reflection symmetry. By fitting the eigenvalues of the effective seesaw mass matrix with the observed neutrino mass-squared differences, we predict the individual light neutrino masses. The vacuum alignment of the $S_4$ triplet appearing in the Majorana mass term plays a key role in obtaining the aforementioned ${\text{TM}}_1$ scenario. Since the symmetries of the flavour group are not sufficient to define this alignment, we apply the recently proposed framework of the auxiliary group in our model. Using this framework, the $S_4$ triplet is obtained by coupling together several irreducible multiplets that transform under an expanded flavour group consisting of the original flavour group as well as an auxiliary group. The vacuum alignment of each of these multiplets is uniquely defined in terms of its residual symmetries under the expanded flavour group. As a result, the $S_4$ triplet constructed from these multiplets also becomes uniquely defined.

   hep-phEur.Phys.J.Plus(2022)·8 citations
8. 08*

   QED background against atomic neutrino process with initial spatial phase

   Minoru Tanaka🇯🇵 · Koji Tsumura🇯🇵 · Noboru Sasao🇯🇵 · Satoshi Uetake🇯🇵 · Motohiko Yoshimura🇯🇵

   Atomic deexcitation emitting a neutrino pair and a photon is expected to provide a novel method of neutrino physics if it is enhanced by quantum coherence in a macroscopic target. However, the same enhancement mechanism may also lead to a serious problem of enhanced QED background process. We show that the QED background can be suppressed enough in the photonic crystal waveguide by using the spatial phase that is imprinted in the process of initial coherence generation in the target at excitation.

   hep-phhep-exphysics.opticsEur.Phys.J.Plus(2020)·3 citations
9. 09*

   Double parton scattering in pA collisions at the LHC revisited

   B.Blok🇮🇱 · F.A. Ceccopieri🇮🇱

   We consider the production of $W$-boson plus dijet, $W$-boson plus b-jets and same sign $WW$ via double parton scattering (DPS) in $pA$ collisions at the LHC and evaluate the corresponding cross sections. The impact of a novel DPS contribution pertinent to $pA$ collisions is quantified. Exploiting the experimental capability of performing measurements differential in the impact parameter in $pA$ collisions, we discuss a method to single out this novel DPS contribution. The method allows the subtraction of the leading twist (LT) single parton scattering background and it gives access in a very clean way to double parton distribution functions in the proton. We calculate leading twist and DPS cross sections and study the dependence of the observables on the cuts in the jets phase space. In the $Wjj$ channel the observation of DPS is possible with data already accumulated in $pA$ runs and the situation will greatly improve for the next high luminosity runs. For the $Wb\bar{b}$ final state, the statistics within the current data is too low, but there is possibility to observe DPS in this channel in future runs, albeit with much reduced sensitivity than in $Wjj$ final state. Finally the DPS observation in the same sign $WW$ channel will require either significant increase of integrated luminosity beyond that foreseen in next $pA$ runs or improved methods for $W$ reconstruction, along with its charge, in hadronic decay channels.

   hep-phhep-exnucl-exnucl-thEPJC(2020)·8 citations
10. 10*

    The three-loop single mass polarized pure singlet operator matrix element

    J. Ablinger🇦🇹 · A. Behring🇩🇪 · J. Blümlein🇩🇪 · A. De Freitas🇩🇪 · A. von Manteuffel🇺🇸 · C. Schneider🇦🇹 · K. Schönwald🇩🇪

    We calculate the massive polarized three-loop pure singlet operator matrix element $A_{Qq}^{(3),\mathrm{PS}}$ in the single mass case in the Larin scheme. This operator matrix element contributes to the massive polarized three-loop Wilson coefficient $H_{Qq}^{(3),\mathrm{PS}}$ in deep-inelastic scattering and constitutes a three-loop transition matrix element in the variable flavor number scheme. We provide analytic results in Mellin $N$ and in $x$ space and study the behaviour of this operator matrix element in the region of small and large values of the Bjorken variable $x$.

    hep-phhep-thNPB(2020)·42 citations
11. 11*

    Understanding $X(3872)$ and its decays in the extended Friedrichs scheme

    Meng-Ting Yu🇨🇳 · Zhi-Yong Zhou🇨🇳 · Zhiguang Xiao🇨🇳

    We present that the $X(3872)$ could be represented as a dynamically generated state in the extended Friedrichs scheme, in which the ratio of "elementariness" and "compositeness" of the different components in the $X(3872)$ is about $Z_{c\bar{c}}:X_{{\bar{D}}^0{D}^{0\ast }}:X_{D^{+}{D}^{-\ast }}:X_{{\bar{D}}^{\ast }{D}^{\ast }}$ $=1:(2.67\sim 8.85):(0.45\sim 0.46):0.04$. Furthermore, its decays to ${\pi }^0$ and a $P$-wave charmonium ${\chi }_{cJ}$ state with $J=0,1$, or $2$, $J/\psi {\pi }^{+}{\pi }^{-}$, and $J/\psi {\pi }^{+}{\pi }^{-}{\pi }^0$ could be calculated out with the help of Barnes-Swanson model. The isospin breaking effects is easily understood in this scheme. This calculation also shows that the decay rate of $X(3872)$ to ${\chi }_{c1}{\pi }^0$ is much smaller than its decay rate to $J/\psi {\pi }^{+}{\pi }^{-}$.

    hep-phhep-exnucl-th0 citations
12. 12*

    Simple differential equations for Feynman integrals associated to elliptic curves

    Stefan Weinzierl🇩🇪

    The $\epsilon$-form of a system of differential equations for Feynman integrals has led to tremendeous progress in our abilities to compute Feynman integrals, as long as they fall into the class of multiple polylogarithms. It is therefore of current interest, if these methods extend beyond the case of multiple polylogarithms. In this talk I discuss Feynman integrals, which are associated to elliptic curves and their differential equations. I show for non-trivial examples how the system of differential equations can be brought into an $\epsilon$-form. Single-scale and multi-scale cases are discussed.

    hep-phhep-th9 citations
13. 13*

    Simple model for large CP violation in charm decays, B-physics anomalies, muon g-2, and Dark Matter

    Lorenzo Calibbi🇨🇳 · Tianjun Li🇨🇳 · Ying Li🇨🇳 · Bin Zhu🇨🇳

    We present a minimal extension of the Standard Model that can simultaneously account for the anomalies in semi-leptonic B meson decays and the muon g-2, give large CP violation in charm decays (up to the value recently measured by LHCb), and provide thermal-relic dark matter, while evading all constraints set by other flavour observables, LHC searches, and dark matter experiments. This is achieved by introducing only four new fields: a vectorlike quark, a vectorlike lepton, and two scalar fields (a singlet and a doublet) that mix due to the electroweak symmetry breaking and provide the dark matter candidate. The singlet-doublet mixing induces chirally-enhanced dipole transitions, which are crucial for the explanation of the muon g-2 discrepancy and the large charm CP violation, and allows to achieve the observed dark matter density in wide regions of the parameter space.

    hep-phJHEP(2020)·39 citations
14. 14*

    Exclusive and diffractive quarkonium -- pair production at the LHC and FCC

    V. P. Goncalves🇧🇷 · R. Palota da Silva🇧🇷

    The production of a quarkonium -- pair in exclusive and diffractive processes in $pp$ collisions at the LHC and FCC energies is investigated. We consider the $J/\Psi J/\Psi$ and ${\rm Y}{\rm Y}$ production in these processes and present predictions for the transverse momentum and rapidity distributions considering the kinematical ranges expected to be covered by central and forward detectors. Results for the cross sections are also presented. Our results indicate that the double $J/\Psi$ production is dominated by the exclusive process, while the double ${\rm Y}$ production receive a large contribution of the diffractive process. The impact of the modelling of the gap survival factor on our predictions is discussed.

    hep-phhep-exPRD(2020)·14 citations
15. 15*

    Triple Higgs production at hadron colliders at NNLO in QCD

    Daniel de Florian🇦🇷 · Ignacio Fabre🇨🇭 · Javier Mazzitelli🇩🇪

    In this work we analyse the triple Higgs boson production cross section at hadron colliders via gluon fusion, and present for the first time the full set of QCD NNLO corrections in the heavy top limit. In order to account for finite top mass effects we perform two different reweighting procedures, and study the dependence of the result on the choice of the approximation. Combining the most accurate predictions available to date, we present the following result for the total NNLO cross section for triple Higgs boson production at a 100 TeV collider: ${\sigma }_{\text{NNLO}}=5.56_{-6\%}^{+5\%}\pm 20\%$ fb, where the first uncertainty is an estimate for higher order effects from scale variations, while the last one is an estimate for the missing finite top mass effects.

    hep-phJHEP(2020)·54 citations
16. 16*

    General Markovian Equation for Scalar Fields in a Slowly Evolving Background

    Gilles Buldgen🇧🇪 · Marco Drewes🇧🇪 · Jin U Kang🇮🇹 · Ui Ri Mun🇰🇵

    We present a general and model-independent method to obtain an effective Markovian quantum kinetic equation for the expectation value of a slowly evolving scalar field in an adiabatically evolving background from first principles of nonequilibrium quantum field theory. The method requires almost no assumptions about the field's interactions and the composition of the background, except that 1) the coupling constants shall be small enough for perturbation theory to be applicable, 2) there is a clear separation between microphysical time scales and the rate at which bulk properties change, and 3) higher time derivatives of the field remain small. The resulting Markovian equation of motion is expressed in terms of an effective potential and friction coefficients. Motivated by cosmological applications we focus on spatially homogeneous and isotropic systems, but the approach could also be applied to spatial gradients.

    hep-phhep-thJCAP(2022)·10 citations
17. 17*

    On axials and pseudoscalars in the hadronic light-by-light contribution to the muon $(g-2)$

    Luigi Cappiello🇮🇹 · Oscar Cata🇩🇪 · Giancarlo D'Ambrosio🇮🇹 · David Greynat · Abhishek Iyer🇮🇹

    Despite recent developments, there are a number of conceptual issues on the hadronic light-by-light (HLbL) contribution to the muon $(g-2)$ which remain unresolved. One of the most controversial ones is the precise way in which short-distance constraints get saturated by resonance exchange, particularly in the so-called Melnikov-Vainshtein (MV) limit. In this paper we address this and related issues from a novel perspective, employing a warped five-dimensional model as a tool to generate a consistent realization of QCD in the large-$N_c$ limit. This approach differs from previous ones in that we can work at the level of an effective action, which guarantees that unitarity is preserved and the chiral anomaly is consistently implemented at the hadronic level. We use the model to evaluate the inclusive contribution of Goldstone modes and axial-vector mesons to the HLbL. We find that both anomaly matching and the MV constraint cannot be fulfilled with a finite number of resonances (including the pion) and instead require an infinite number of axial-vector states. Our numbers for the HLbL point at a non-negligible role of axial-vector mesons, which is closely linked to a correct implementation of QCD short-distance constraints.

    hep-phPRD(2020)·110 citations
18. 18*

    Nucleus Capture by Macroscopic Dark Matter

    Yang Bai🇺🇸 · Joshua Berger🇺🇸

    For a class of macroscopic dark matter with a large interaction strength with Standard Model particles, a nucleus could be captured by the dense, heavy dark matter as it traverses ordinary material. The radiated photon carries most of the binding energy and is a characteristic signature for dark matter detection. We develop analytic formulas and present numerical results for this radiative capture process in the low energy, non-dipole limit. Large-volume neutrino detectors like NO$\nu$A, JUNO, DUNE and Super(Hyper)-K may detect multi-hit or single-hit radiative capture events and can search for dark matter up to one gram in mass.

    hep-phhep-exJHEP(2020)·33 citations
19. 19*

    Dark Matter-Electron Scattering from Aromatic Organic Targets

    Carlos Blanco🇺🇸 · J.I. Collar🇺🇸 · Yonatan Kahn🇺🇸 · Benjamin Lillard🇺🇸

    Sub-GeV dark matter (DM) which interacts with electrons can excite electrons occupying molecular orbitals in a scattering event. In particular, aromatic compounds such as benzene or xylene have an electronic excitation energy of a few eV, making them sensitive to DM as light as a few MeV. These compounds are often used as solvents in organic scintillators, where the de-excitation process leads to a photon which propagates until it is absorbed and re-emitted by a dilute fluor. The fluor photoemission is not absorbed by the bulk, but is instead detected by a photon detector such as a photomultiplier tube. We develop the formalism for DM-electron scattering in aromatic organic molecules, calculate the expected rate in p-xylene, and apply this calculation to an existing measurement of the single photo-electron emission rate in a low-background EJ-301 scintillator cell. Despite the fact that this measurement was performed in a shallow underground laboratory under minimal overburden, the DM-electron scattering limits extracted from these data are already approaching leading constraints in the 3-100 MeV DM mass range. We discuss possible next steps in the evolution of this direct detection technique, in which scalable organic scintillators are used in solid or liquid crystal phases and in conjunction with semiconductor photodetectors to improve sensitivity through directional signal information and potentially lower dark rates.

    hep-phhep-exPRD(2020)·95 citations
20. 20*

    Spontaneous Freeze Out of Dark Matter From an Early Thermal Phase Transition

    Lucien Heurtier🇺🇸 · Herve Partouche🇫🇷

    We propose a new paradigm for the thermal production of dark matter in the early universe, in which dark-matter particles acquire their mass and freeze out spontaneously from the thermal bath after a dark phase transition takes place. The decoupling arises because the dark-matter particles become suddenly non-relativistic and not because of any decay channel becoming kinematically close. We propose a minimal scenario in which a scalar and a fermionic dark-matter are in thermal equilibrium with the Standard-Model bath. We compute the finite temperature corrections to the scalar potential and identify a region of the parameter space where the fermionic dark-matter mass spontaneously jumps over the temperature when the dark phase transition happens. We explore the phenomenological implications of such a model in simple cases and show that the annihilation cross section of dark-matter particles has to be larger by more than one order of magnitude as compared to the usual constant-mass WIMP scenario in order to accomodate the correct relic abundance. We show that in the spontaneous freeze out regime a TeV-scale fermionic dark-matter that annihilates into leptons through s-wave processes can be accessible to detection in the near future.

    hep-phastro-ph.HEhep-thPRD(2020)·33 citations
21. 21*

    Filtered Dark Matter at a First Order Phase Transition

    Michael J. Baker (Univeristy of Melbourne)🇦🇺 · Joachim Kopp (CERN & JGU Mainz)🇨🇭 · Andrew J. Long (Rice University)🇺🇸

    We describe a new mechanism of dark matter production in the early Universe, based on the dynamics of a first order phase transition. We assume that dark matter particles acquire mass during the phase transition, making it energetically unfavourable for them to enter the expanding bubbles of the massive phase. Instead, most of them are reflected off the advancing bubble walls and quickly annihilate away in the massless phase. The bubbles eventually merge as the phase transition is completed, and only the dark matter particles which have entered the bubbles survive to constitute the observed dark matter today. This mechanism can produce dark matter with masses from the GeV scale to above the PeV scale, including a large region of viable parameter space beyond the Griest--Kamionkowski bound. Current and future direct detection and collider experiments can probe much of the viable parameter space.

    hep-phPRL(2020)·144 citations
22. 22*

    Analytical solution to DGLAP integro-differential equation via complex maps in domains of contour integrals

    Gustavo Alvarez🇩🇪 · Igor Kondrashuk🇨🇱

    A simple model for QCD dynamics in which the DGLAP integro-differential equation may be solved analytically has been considered in our previous papers arXiv:1611.08787 [hep-ph] and arXiv:1906.07924 [hep-ph]. When such a model contains only one term in the splitting function of the dominant parton distribution, then Bessel function appears to be the solution to this simplified DGLAP equation. To our knowledge, this model with only one term in the splitting function for the first time has been proposed by Blumlein in hep-ph/9506403. In arXiv:1906.07924 [hep-ph] we have shown that a dual integro-differential equation obtained from the DGLAP equation by a complex map in the plane of the Mellin moment in this model may be considered as the BFKL equation. Then, in arXiv:1906.07924 we have applied a complex diffeomorphism to obtain a standard integral from Gradshteyn and Ryzhik tables starting from the contour integral for parton distribution functions that is usually taken by calculus of residues. This standard integral from these tables appears to be the Laplace transformation of Jacobian for this complex diffeomorphism. Here we write up all the formulae behind this trick in detail and find out certain important points for further development of this strategy. We verify that the inverse Laplace transformation of the Laplace image of the Bessel function may be represented in a form of Barnes contour integral.

    ↳ hep-thhep-phmath-phmath.MPJ.Phys.Comm.(2020)·10 citations
23. 23*

    Zb tetraquark channel from lattice QCD and Born-Oppenheimer approximation

    S. Prelovsek🇸🇮 · H. Bahtiyar🇹🇷 · J. Petkovic🇸🇮

    Two $Z_b$ hadrons with exotic quark structure $\bar{b}b\bar{d}u$ were discovered by Belle experiment. We present a lattice QCD study of the $\bar{b}b\bar{d}u$ system in the approximation of static $b$ quarks, where the total spin of heavy quarks is fixed to one. The energies of eigenstates are determined as a function of the separation $r$ between $b$ and $\bar{b}$. The lower eigenstates are related to a bottomonium and a pion. The eigenstate dominated by $B{\bar{B}}^{\ast }$ has energy significantly below $m_B+m_{B^{\ast }}$, which points to a sizable attraction for small $r$. The attractive potential $V(r)$ between $B$ and ${\bar{B}}^{\ast }$ is extracted assuming that this eigenstate is related exclusively to $B{\bar{B}}^{\ast }$. The Schrödinger equation for $B{\bar{B}}^{\ast }$ within the extracted potential leads to one bound state below $B{\bar{B}}^{\ast }$ threshold, whose mass depends on the parametrization of the lattice potential. For certain parametrizations, the bound state is very close to the $B{\bar{B}}^{\ast }$ threshold and renders a narrow peak in the $B{\bar{B}}^{\ast }$ rate above threshold - these features could be related to $Z_b(10610)$ in the experiment.

    ↳ hep-lathep-phPLB(2020)·39 citations
24. 24*

    Primordial Black Holes as Dark Matter through Higgs Criticality

    Samuel Passaglia🇺🇸 · Wayne Hu🇺🇸 · Hayato Motohashi🇯🇵

    We study the dynamics of a spectator Higgs field which stochastically evolves during inflation onto near-critical trajectories on the edge of a runaway instability. We show that its fluctuations do not produce primordial black holes (PBHs) in sufficient abundance to be the dark matter, nor do they produce significant second-order gravitational waves. First we show that the Higgs produces larger fluctuations on CMB scales than on PBH scales, itself a no-go for a viable PBH scenario. Then we track the superhorizon perturbations nonlinearly through reheating using the delta N formalism to show that they are not converted to large curvature fluctuations. Our conclusions hold regardless of any fine-tuning of the Higgs field for both the Standard Model Higgs and for Higgs potentials modified to prevent unbounded runaway.

    ↳ astro-ph.COgr-qchep-phhep-thPRD(2020)·18 citations
25. 25*

    Strong Soft X-ray Excess in 2015 XMM-Newton Observation of BL--Lac OJ~287

    Main Pal · Pankaj Kushwaha · Gulab C. Dewangan · P. K. Pawar

    We report a strong soft X-ray excess in the BL--Lacartae $\gamma$-ray blazar OJ~287 during the long exposure in May 2015, amongst two of the latest \xmm~{} observations performed in May 2015 and 2018. In case of May 2015 observation, a logparabola model fits the EPIC-pn data well while a logparabola plus powerlaw describes the overall simultaneous optical to X-ray spectra, suggesting the excess as the synchrotron tail. This interpretation, however, is inconsistent with the observed spectral break between near-infrared and optical spectra, attributed to standard disk around a supermassive black hole (SMBH). Based on this, we considered two commonly invoked accretion disk based models in AGNs to explain the soft excess: the cool Comptonization component in the accretion disk and the blurred reflection from the partially ionized accretion disk. We found that both cool Comptonization and blurred reflection models provide equally good fit to the data and favor a super-heavy SMBH of mass $\sim 10^{10}{M}_{\odot }$. Further investigation of about a month long simultaneous X-ray and UV pointing observations revealed a delayed UV emission with respect to the 1.5-10 keV band, favoring X-ray reprocessing phenomenon as the dominant mechanism. The results suggest that the soft excess is probably caused by strong light bending close to the SMBH. The detected soft excess in 2015 data and its disappearance in 2018 data is also consistent with the presence of accretion disk emission, inferred from the NIR-optical spectral} break between May 2013 to March 2016.

    ↳ astro-ph.HEhep-phApJ(2020)·24 citations
26. 26*

    Particle Generative Adversarial Networks for full-event simulation at the LHC and their application to pileup description

    Jesus Arjona Martinez🇬🇧 · Thong Q Nguyen🇺🇸 · Maurizio Pierini🇨🇭 · Maria Spiropulu🇺🇸 · Jean-Roch Vlimant🇺🇸

    We investigate how a Generative Adversarial Network could be used to generate a list of particle four-momenta from LHC proton collisions, allowing one to define a generative model that could abstract from the irregularities of typical detector geometries. As an example of application, we show how such an architecture could be used as a generator of LHC parasitic collisions (pileup). We present two approaches to generate the events: unconditional generator and generator conditioned on missing transverse energy. We assess generation performances in a realistic LHC data-analysis environment, with a pileup mitigation algorithm applied.

    ↳ hep-exhep-phJ.Phys.Conf.Ser.(2020)·47 citations
27. 27*

    de Sitter Minima from M theory and String theory

    Niccolò Cribiori🇦🇹 · Renata Kallosh🇺🇸 · Andrei Linde🇺🇸 · Christoph Roupec🇦🇹

    We study M-theory compactification on ${\mathbb{T}}^7/{\mathbb{Z}}_2^3$ in the presence of a seven-flux, metric fluxes and KK monopoles. The effective four-dimensional supergravity has seven chiral multiplets whose couplings are specified by the $G_2$-structure of the internal manifold. We supplement the corresponding superpotential by a KKLT type non-perturbative exponential contribution for all, or for some of the seven moduli, and find a discrete set of supersymmetric Minkowski minima. We also study type IIA and type IIB string theory compactified on ${\mathbb{T}}^6/{\mathbb{Z}}_2^2$. In type IIA, we use a six-flux, geometric fluxes and non-perturbative exponents. In type IIB theory, we use F and H fluxes, and non-geometric Q and P fluxes, corresponding to consistently gauged supergravity with certain embedding tensor components, \emph{without non-perturbative exponents}. Also in these situations, we produce discrete Minkowski minima. Finally, to construct dS vacua starting from these Minkowski progenitors, we follow the procedure of mass production of dS vacua.

    ↳ hep-thgr-qchep-phPRD(2020)·22 citations
28. 28*

    A CMB Millikan Experiment with Cosmic Axiverse Strings

    Prateek Agrawal🇺🇸 · Anson Hook🇺🇸 · Junwu Huang🇨🇦

    We study axion strings of hyperlight axions coupled to photons. Hyperlight axions -- axions lighter than Hubble at recombination -- are a generic prediction of the string axiverse. These axions strings produce a distinct quantized polarization rotation of CMB photons which is $\mathcal{O}({\alpha }_{\mathrm{em}})$. As the CMB light passes many strings, this polarization rotation converts E-modes to B-modes and adds up like a random walk. Using numerical simulations we show that the expected size of the final result is well within the reach of current and future CMB experiments through the measurement of correlations of CMB B-modes with E- and T-modes. The quantized polarization rotation angle is topological in nature and can be seen as a geometric phase. Its value depends only on the anomaly coefficient and is independent of other details such as the axion decay constant. Measurement of the anomaly coefficient by measuring this rotation will provide information about the UV theory, such as the quantization of electric charge and the value of the fundamental unit of charge. The presence of axion strings in the universe relies only on a phase transition in the early universe after inflation, after which the string network rapidly approaches an attractor scaling solution. If there are additional stable topological objects such as domain walls, axions as heavy as $10^{-15}$ eV would be accessible. The existence of these strings could also be probed by measuring the relative polarization rotation angle between different images in gravitationally lensed quasar systems.

    ↳ astro-ph.COastro-ph.GAhep-phhep-thJHEP(2020)·85 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.