Fri·Oct 11, 2019Friday·October 11, 2019

1. 01*

   Helicity-dependent generalization of the JIMWLK evolution

   Florian Cougoulic🇺🇸 · Yuri V. Kovchegov🇺🇸

   We generalize the JIMWLK evolution equation to include the small-$x$ evolution of helicity distributions. To derive helicity JIMWLK, we use the method devised by A.H. Mueller for the usual unpolarized JIMWLK, and apply it to the helicity evolution equations derived earlier. We obtain a functional evolution equation for the generalized JIMWLK weight functional. The functional now is a sum of a helicity-independent term and a helicity-dependent term. The kernel of the new evolution equation consists of the standard eikonal leading-order JIMWLK kernel plus new terms containing derivatives with respect to the sub-eikonal quark and gluon fields. The new kernel we derive can be used to generate the standard JIMWLK evolution and to construct small-$x$ evolution equations for flavor-singlet operators made of any number of light-cone Wilson lines along with one Wilson line containing sub-eikonal helicity-dependent local operator insertions (a "polarized Wilson line").

   hep-phnucl-thPRD(2019)·80 citations
2. 02*

   Dark Matter Bound State Formation in Fermionic $Z_2$ DM model with Light Dark Photon and Dark Higgs Boson

   Pyungwon Ko🇰🇷 · Toshinori Matsui🇰🇷 · Yi-Lei Tang🇰🇷

   If fermionic dark matter (DM) is stabilized by dark $U(1)$ gauge symmetry that is spontaneously broken into its subgroup $Z_2$, the particle contents of the model becomes very rich: DM and excited DM, both of them are Majorana fermions, as well as two dark force mediators, dark photon and dark Higgs boson are naturally present due to the underlying dark gauge symmetry. In this paper, we study the DM bound state formation processes within this scenario, assuming both dark photon and dark Higgs are light mediators and including the effects of excited DM. The Goldstone boson contributions to the potential matrix in the Schrödinger equations are found to be important. The emissions of a longitudinal vector boson (or somehow equivalently a Goldstone boson) during the DM bound state formations are crucial to induce a significant reannihilation process, reducing the dark matter relic abundance. Most of the stringent constraints for this kind of dark matter considered in the literature are simply evaded.

   hep-phJHEP(2020)·32 citations
3. 03*

   Spectroscopy of excited charmed mesons

   Mohammad H. Alhakami🇸🇦

   We derive mass formulas for the $P$-wave orbitally excited $D_{0(s)}^{\ast }$, $D_{1(s)}^{\prime }$, $D_{1(s)}$, and $D_{2(s)}^{\ast }$ heavy charmed mesons including all effects from one-loop corrections that contribute at leading order in chiral expansion. In our formalism, the effects to first order in $m_q$, where $m_q$ is the light quark mass, and to first order in $m_c^{-1}$, where $m_c$ is the charm quark mass, and $m_q/m_c$ terms are considered. The experimental and lattice QCD results on the charmed meson spectra are employed to fix the large number of counterterms appearing in the effective chiral Lagrangian used in this work. This allows us to test the validity of perturbative expansion of our theory. The results presented in the current paper are useful to other applications of excited charmed and bottom meson systems.

   hep-phPRD(2020)·7 citations
4. 04*

   Magic neutrino mass model with broken $\mu -\tau$ symmetry and Leptogenesis

   Surender Verma🇮🇳 · Monal Kashav🇮🇳

   We investigate baryogenesis via leptogenesis in $A_4$ flavor model within the paradigm of type-I and II seesaw mechanism resulting in magic neutrino mass matrix with broken $\mu -\tau$ symmetry in a minimal scenario with two right-handed neutrinos(2RHN). Additional $Z_3$ cyclic symmetry is employed to constrain the Yukawa structure of model. The type-II seesaw terms play crucial role in generating non-degenerate neutrino masses and non-zero ${\theta }_{13}$ and contribute in baryogenesis. In particular, after the spontaneous symmetry breaking, the Yukawa couplings $y_{{\Delta }_1}$ and $y_{{\Delta }_3}$ are responsible for the breaking of $\mu -\tau$ symmetry. The effective Majorana neutrino mass $|M_{ee}|$ is found to be well within the sensitivity reach of the $0\nu \beta \beta$ experiments, in particular, for inverted hierarchy. The model has imperative implication for inverted hierarchy, for example, the non-observation of this process at nEXO will rule out IH. The predicted baryon asymmetry is in good agreement with the observed baryon asymmetry for NH whereas IH is disallowed at 2.5$\sigma$ C.L..

   hep-phJ.Phys.G(2020)·16 citations
5. 05*

   Photoproductions of dileptons, photons, and light vector mesons in p-p, p-Pb, and Pb-Pb collisions at Large Hadron Collider energies

   Zhi-Lei Ma🇨🇳 · Zhun Lu🇨🇳 · Jia-Qing Zhu🇨🇳 · Li Zhang🇨🇳

   The photoproduction of large $p_T$ dileptons, photons and light vector mesons in p-p, p-Pb and Pb-Pb collisions at LHC energies is studied, where the fragmentation processes and the ultra-incoherent photon channel are included. An exact treatment is developed for photoproduction processes in heavy ion collisions, which recovers the equivalent photon approximation (EPA) in the limit $Q^2\to 0$ and can avoid double counting effectively. The full kinematical relations are also achieved. We present the results as the distributions in $Q^2$, $p_T$ and $y_r$, the total cross sections are also estimated. The numerical results indicate that: the contribution of photoproduction processes is evident in the large $p_T$ and $y_r$ regions, and starts to play a fundamental role in p-Pb collisions. The ultra-incoherent photon emission is a important channel of photoproduction processes, which can provide the meaningful contributions. EPA is only applicable in small $y$ and $Q^2$ domains, and is very sensitive to the values of $y_{\max }$ and $Q_{\max }^2$. The EPA errors appear when $y>0.29$ and $Q^2>0.1{\mathrm{GeV}}^2$, and are rather serious in p-Pb and Pb-Pb collisions. When dealing with widely kinematical regions, the exact treatment needs to be adopted.

   hep-phPRD(2021)·7 citations
6. 06*

   Probing light Yukawa couplings in Higgs pair production

   Lina Alasfar🇩🇪 · Ramona Gröber🇩🇪

   One of the puzzles of the SM is the large hierarchy between the Yukawa couplings of different flavours. Yukawa couplings of the first and the second generation are constrained only very weakly so far. However, one can obtain large deviations in the Yukawa couplings in several New Physics (NP) models, such as e.g. models with new vector-like quarks, or new Higgs bosons that couple naturally to individual fermion families. In this work, we investigate the potential bounds on the NP Higgs Yukawa couplings modification ${\kappa }_f$ for light quarks from double-Higgs at the LHC, starting from a model independent formalism. We have looked at the two Higgs boson final state $b\bar{b}\gamma \gamma$, and the relevant experimental cuts to reduce backgrounds and estimated the potential exclusion bounds for ${\kappa }_f$. We have considered both linear and non-linear effective field theory for the Higgs light quark coupling modifications.

   hep-phhep-exPoS(2020)·1 citation
7. 07*

   Dalitz-plot decomposition for three-body decays

   JPAC Collaboration: M. Mikhasenko🇨🇭 · M. Albaladejo🇺🇸 · L. Bibrzycki🇺🇸 · C. Fernandez-Ramirez🇲🇽 · V. Mathieu🇪🇸 · S. Mitchell🇬🇧 · M. Pappagallo🇬🇧 · A. Pilloni🇮🇹 · D. Winney🇺🇸 · T. Skwarnicki🇺🇸 · A. P. Szczepaniak🇺🇸

   We present a general formalism to write the decay amplitude for multibody reactions with explicit separation of the rotational degrees of freedom, which are well controlled by the spin of the decay particle, and dynamic functions on the subchannel invariant masses, which require modeling. Using the three-particle kinematics we demonstrate the proposed factorization, named the Dalitz-plot decomposition. The Wigner rotations, that are subtle factors needed by the isobar modeling in the helicity framework, are simplified with the proposed decomposition. Consequently, we are able to provide them in an explicit form suitable for the general case of arbitrary spins. The only unknown model-dependent factors are the isobar lineshapes that describe the subchannel dynamics. The advantages of the new decomposition are shown through three examples relevant for the recent discovery of the exotic charmonium candidate $Z_c(4430)$, the pentaquarks $P_c$, and the intriguing ${\Lambda }_c^{+}\to p{K}^{-}{\pi }^{+}$ decay.

   hep-phPRD(2020)·49 citations
8. 08*

   Analytical results for hadronic contributions to the muon $g-2$

   Johan Bijnens🇸🇪 · Nils Hermansson-Truedsson🇸🇪 · Antonio Rodriguez-Sánchez🇸🇪

   This talk discusses two analytical calculations relevant for the Standard Model calculation of the muon $g-2$. The first part is the recent derivation of the quark-loop as the first term in a well-defined operator-product expansion for the short-distance part of the hadronic light-by-light contribution, as well as the calculation of the next term. The second part is the calculation of finite volume effects relevant for lattice QCD calculations of the electromagnetic contribution to the lowest-order hadronic vacuum-polarization contribution and the proof they only start at $1/L^3$.

   hep-phPoS(2020)·0 citations
9. 09*

   New solutions of viscous relativistic hydrodynamics

   Mate Csanad🇭🇺 · Marton I. Nagy🇭🇺 · Ze-Fang Jiang🇨🇳 · Tamas Csorgo🇭🇺

   Relativistic hydrodynamics represents a powerful tool to investigate the time evolution of the strongly interacting quark gluon plasma created in ultrarelativistic heavy ion collisions. The equations are solved often numerically, and numerous analytic solutions also exist. However, the inclusion of viscous effects in exact, analytic solutions has received less attention. Here we utilize Hubble flow to investigate the role of bulk viscosity, and present different classes of exact, analytic solutions valid also in the presence of dissipative effects.

   hep-phnucl-thPhys.Part.Nucl.(2020)·1 citation
10. 10*

    Eternal Inflation and Reheating in the Presence of the Standard Model Higgs Field

    Mudit Jain🇺🇸 · Mark P. Hertzberg🇺🇸

    We study the details of eternal inflation in the presence of a spectator Higgs field within the framework of the minimal Standard Model. We have recently shown that in the presence of scalar field(s) which allow inflation only within a finite domain of field values, the universe reaches a steady state where the normalized distribution for the field(s) converges to a steady state distribution [1]. In this paper, we analyze this eternal inflation scenario with the renormalized Standard Model Higgs potential, since it also allows inflation in a finite domain, but turns over at high scales due to the running of the self-coupling, marking an exit from inflation. We compute the full steady state distribution for the Higgs using an integral evolution technique that we formulated in [1] and the fractal dimension of the universe. We then obtain a bound on the inflationary Hubble scale in order to have a large observable universe contained within the instability scale of $H\lesssim \mathcal{O}(10^9)$GeV depending on the top mass. Upon reheating of the universe, thermal fluctuations in the Higgs field could potentially pose another problem; however, we compute the rate of thermal bubble production and find that the probability of tunneling in the post-inflationary era is negligibly small even for very high reheat temperatures.

    hep-phastro-ph.COgr-qchep-thPRD(2020)·16 citations
11. 11*

    Diffractive photoproduction of $J/\psi$ and ${\rm Y}$ using holographic QCD: gravitational form factors and GPD of gluons in the proton

    Kiminad A. Mamo🇺🇸 · Ismail Zahed🇺🇸

    We present a holographic analysis of diffractive photoproducton of charmonium $J/\psi$ and upsilonium ${\rm Y}$ on a proton, considered as a bulk Dirac fermion, for all ranges of $\sqrt{s}$, i.e., from near threshold to very high energy. Using the bulk wave functions of the proton and vector mesons, within holographic QCD, and employing Witten diagrams in the bulk, we compute the diffractive photoproduction amplitude of $J/\psi$ and ${\rm Y}$. The holographic amplitude shows elements of the strictures of vector meson dominance (VMD). It is dominated by the exchange of a massive graviton or $2^{++}$ glueball resonances near threshold, and its higher spin-j counterparts that reggeize at higher energies. Both the differential and total cross sections are controlled by the gravitational form factor $A(t)$, and compare well to the recent results reported by the GlueX collaboration near threshold and the world data at large $\sqrt{s}$. The holographic gravitational form factors, including the D-term, which is due to the exchange of massive spin-0 glueballs, are in good agreement with lattice simulations. We use it to extract the holographic pressure and shear forces inside the proton. Finally, using a pertinent integral representation of the holographic gravitational form factor $A(t)$ near threshold, and its Pomeron counterpart way above threshold, we extract the generalized parton distribution (GPD) of gluons inside the proton at different resolutions.

    hep-phhep-thnucl-thPRD(2020)·139 citations
12. 12*

    Parton Density Uncertainties and the Determination of Electroweak Parameters at Hadron Colliders

    E. Bagnaschi🇨🇭 · A. Vicini🇮🇹

    We discuss the determination of electroweak parameters from hadron collider observables, focusing on the $W$ boson mass measurement. We revise the procedures adopted in the literature to include in the experimental analysis the uncertainty due to our imperfect knowledge of the proton structure. We show how the treatment of the proton parton density functions (PDFs) uncertainty as a source of systematic error, leads to the automatic inclusion in the fit of the bin-bin correlation of the kinematic distributions with respect to PDF variations. In the case of the determination of $M_W$ from the charged lepton transverse momentum distribution, we observe that the inclusion of this correlation factor yields a strong reduction of the PDF uncertainty, given a sufficiently good control over all the other error sources. This improvement depends on a systematic accounting of the features of the QCD-based PDF model, and it is achieved relying only on the information available in current PDF sets. While a realistic quantitative estimate requires to take into account the details of the experimental systematics, we argue that, in perspective, the proton PDF uncertainty will not be a bottleneck for precision measurements.

    hep-phhep-exPRL(2021)·27 citations
13. 13*

    On the phenomenology of sphaleron-induced processes at the LHC and beyond

    Andreas Papaefstathiou🇳🇱 · Simon Plätzer🇦🇹 · Kazuki Sakurai🇵🇱

    We investigate the phenomenological aspects of non-perturbative baryon- and lepton-number-violating processes at hadron colliders. Such processes, induced by instanton/sphaleron configurations of the electroweak gauge fields, are believed to play a crucial role in the generation of baryon asymmetry in the early Universe at finite temperature. On the other hand, at colliders (that represent the zero-temperature high-energy regime) the rate and observability of such processes are still under debate. Motivated by current theoretical considerations, we construct a modern event generator within the general-purpose Herwig Monte Carlo framework, that aims to capture the most relevant features of the dominant processes. We perform a detailed phenomenological analysis focussing on the Large Hadron Collider, at 13 TeV proton-proton centre-of-mass energy, a potential high-energy upgrade at 27 TeV and the proposed Future Circular Collider (FCC-hh) at 100 TeV. We derive constraints on the expected rates for various parametrisations of our model. We find that all three colliders are capable of providing meaningful information on the nature of instanton/sphaleron-induced processes at various energy scales.

    hep-phJHEP(2019)·18 citations
14. 14*

    Stochastic Gravitational Wave Background from Global Cosmic Strings

    Chia-Feng Chang🇺🇸 · Yanou Cui🇺🇸

    Global cosmic strings are generically predicted in particle physics beyond the Standard Model, e.g., a post-inflationary global $U(1)$ symmetry breaking which may associate with axion-like dark matter. We demonstrate that although subdominant to Goldstone emission, gravitational waves (GWs) radiated from global strings can be observable with current or future GW detectors. The frequency spectrum of such GWs is also shown to be a powerful tool to probe the Hubble expansion rate of the Universe at times prior to the Big Bang nucleosynthesis where the standard cosmology has yet to be tested.

    hep-phastro-ph.COgr-qchep-thPhys.Dark Univ.(2020)·97 citations
15. 15*

    The EFT and FCNC interpretations in the processes with top quarks at CMS

    Kirill Skovpen (on behalf of the CMS Collaboration)🇧🇪

    In absence of any distinct evidence of new physics phenomena at the LHC, an increasing number of experimental studies aim at probing anomalous effects with an effective field theory (EFT) that represents a comprehensive approach for interpretation of various experimental results. The processes with the production of top quarks are sensitive to several classes of EFT operators including the flavour-changing neutral currents (FCNC). The summary of the latest CMS results based on the recent studies of the standard model processes and searches for new physics effects involving top quarks are presented.

    ↳ hep-exhep-phPoS(2020)·0 citations
16. 16*

    Learning neutrino effects in Cosmology with Convolutional Neural Networks

    Elena Giusarma🇺🇸 · Mauricio Reyes Hurtado🇺🇸 · Francisco Villaescusa-Navarro🇺🇸 · Siyu He🇺🇸 · Shirley Ho🇺🇸 · ChangHoon Hahn🇺🇸

    Measuring the sum of the three active neutrino masses, $M_{\nu }$, is one of the most important challenges in modern cosmology. Massive neutrinos imprint characteristic signatures on several cosmological observables in particular on the large-scale structure of the Universe. In order to maximize the information that can be retrieved from galaxy surveys, accurate theoretical predictions in the non-linear regime are needed. Currently, one way to achieve those predictions is by running cosmological numerical simulations. Unfortunately, producing those simulations requires high computational resources -- several hundred to thousand core-hours for each neutrino mass case. In this work, we propose a new method, based on a deep learning network, to quickly generate simulations with massive neutrinos from standard $\Lambda$CDM simulations without neutrinos. We computed multiple relevant statistical measures of deep-learning generated simulations, and conclude that our approach is an accurate alternative to the traditional N-body techniques. In particular the power spectrum is within $\simeq 6\%$ down to non-linear scales $k=0.7$~\rm h/Mpc. Finally, our method allows us to generate massive neutrino simulations 10,000 times faster than the traditional methods.

    ↳ astro-ph.COcs.LGhep-phApJ(2023)·39 citations
17. 17*

    MOND vs. dark matter in light of historical parallels

    Mordehai Milgrom🇮🇱

    MOND is a paradigm that contends to account for the mass discrepancies in the Universe without invoking `dark' components, such as `dark matter' and `dark energy'. It does so by supplanting Newtonian dynamics and General Relativity, departing from them at very low accelerations. Having in mind readers who are historians and philosophers of science, as well as physicists and astronomers, I describe in this review the main aspects of MOND -- its statement, its basic tenets, its main predictions, and the tests of these predictions -- contrasting it with the dark-matter paradigm. I then discuss possible wider ramifications of MOND, for example the potential significance of the MOND constant, $a_0$, with possible implications for the roots of MOND in cosmology. Along the way I point to parallels with several historical instances of nascent paradigms. In particular, with the emergence of the Copernican world picture, that of quantum physics, and that of relativity, as regards their initial advent, their development, their schematic structure, and their ramifications. For example, the interplay between theories and their corollary laws, and the centrality of a new constant with converging values as deduced from seemingly unrelated manifestations of these laws. I demonstrate how MOND has already unearthed a number of unsuspected laws of galactic dynamics (to which, indeed, $a_0$ is central) predicting them a priori, and leading to their subsequent verification. I parallel the struggle of the new with the old paradigms, and the appearance of hybrid paradigms at such times of struggle. I also try to identify in the history of those established paradigms a stage that can be likened to that of MOND today.

    ↳ astro-ph.GAgr-qchep-phphysics.hist-phStud.Hist.Phil.Sci.B(2020)·76 citations
18. 18*

    Continuum Goldstone spectrum of two-color QCD at finite density with staggered quarks

    Jonas Wilhelm🇩🇪 · Lukas Holicki🇩🇪 · Dominik Smith🇩🇪 · Björn Wellegehausen🇩🇪 · Lorenz von Smekal🇩🇪

    We carry out lattice simulations of two-color QCD and spectroscopy at finite density with two flavors of rooted-staggered quarks and a diquark source term. As in a previous four-flavor study, for small values of the inverse gauge coupling we observe a Goldstone spectrum which reflects the symmetry-breaking pattern of a Gaussian symplectic chiral random-matrix ensemble (GSE) with Dyson index ${\beta }_D=4$, which corresponds to any-color QCD with adjoint quarks in the continuum instead of QC${}_2$D wih fundamental quarks. We show that this unphysical behavior occurs only inside of the bulk phase of $SU(2)$ gauge theory, where the density of $Z_2$ monopoles is high. Using an improved gauge action and a somewhat larger inverse coupling to suppress these monopoles, we demonstrate that the continuum Goldstone spectrum of two-color QCD, corresponding to a Gaussian orthogonal ensemble (GOE) with Dyson index ${\beta }_D=1$, is recovered also with rooted-staggered quarks once simulations are performed away from the bulk phase. We further demonstrate how this change of random-matrix ensemble is reflected in the distribution of eigenvalues of the Dirac operator. By computing the unfolded level spacings inside and outside of the bulk phase, we demonstrate that, starting with the low-lying eigenmodes which determine the infrared physics, the distribution of eigenmodes continuously changes from the GSE to the GOE one as monopoles are suppressed.

    ↳ hep-lathep-phhep-thPRD(2019)·33 citations
19. 19*

    Spectator induced electromagnetic effects in heavy-ion collisions and space-time-momentum conditions for pion emission

    V.Ozvenchuk🇵🇱 · A.Rybicki🇵🇱 · A.Szczurek🇵🇱 · A.Marcinek🇵🇱 · M.Kiełbowicz🇵🇱

    We present our calculation of electromagnetic effects, induced by the spectator charge on Feynman-$x_F$ distributions of charged pions in peripheral $Pb+Pb$ collisions at CERN SPS energies, including realistic initial space-time-momentum conditions for pion emission. The calculation is performed in the framework of our simplified implementation of the fire-streak model, adopted to the production of both ${\pi }^{-}$ and ${\pi }^{+}$ mesons. Isospin effects are included to take into account the asymmetry in production of ${\pi }^{+}$ and ${\pi }^{-}$ at high rapidity. A comparison to a simpler model from the literature is made. We obtain a good description of the NA49 data on the $x_F$- and $p_T$-dependence of the ratio of cross sections ${\pi }^{+}/{\pi }^{-}$. The experimental data favors short times ($0.5<\tau <2$~fm/$c$) for fast pion creation in the local fire-streak rest frame. The possibility of the expansion of the spectators is considered in our calculation, and its influence on the electromagnetic effect observed for the ${\pi }^{+}/{\pi }^{-}$ ratio is discussed. In addition we discuss the relation between anisotropic flow and the electromagnetic distortion of ${\pi }^{+}/{\pi }^{-}$ ratios, and study the influence of transverse expansion of fire streaks as well as their vorticity on this distortion. In this latter study we find that inclusion of rotation of fire streaks in our model gives a satisfactory description of the rapidity dependence of pion directed flow. We conclude that {our implementation of the} fire-streak model, which properly describes the centrality dependence of ${\pi }^{-}$ rapidity spectra at CERN SPS energies, also provides a quantitative description of the electromagnetic effect on the ${\pi }^{+}/{\pi }^{-}$ ratio as a function of $x_F$.

    ↳ nucl-thhep-phPRC(2020)·9 citations
20. 20*

    The synergy between CMB spectral distortions and anisotropies

    Matteo Lucca🇧🇪 · Nils Schöneberg🇩🇪 · Deanna C. Hooper🇩🇪 · Julien Lesgourgues🇩🇪 · Jens Chluba🇬🇧

    Spectral distortions and anisotropies of the CMB provide independent and complementary probes to study energy injection processes in the early universe. Here we discuss the synergy between these observables, and show the promising future of spectral distortion missions to constrain both exotic and non-exotic energy injections. We show that conventional probes such as Big Bang Nucleosynthesis and CMB anisotropies can benefit from and even be surpassed by future spectral distortion experiments. For this, we have implemented a unified framework within the Boltzmann code CLASS to consistently treat the thermal evolution of photons and baryons. Furthermore, we give an extensive and pedagogical introduction into the topic of spectral distortions and energy injections throughout the thermal history of the universe, highlighting some of their unique features and potential as a novel probe for cosmology and particle physics.

    ↳ astro-ph.COgr-qchep-phJCAP(2020)·128 citations
21. 21*

    Observing the deformation of nuclei with relativistic nuclear collisions

    Giuliano Giacalone🇫🇷

    I show that particle collider experiments on relativistic nuclear collisions can serve as direct probes of the deformation of the colliding nuclear species. I argue that collision events presenting very large multiplicities of particles and very small values of the average transverse momentum of the emitted hadrons probe collision geometries in which the nuclear ellipsoids fully overlap along their longer side. By looking at these events one selects interaction regions whose elliptic anisotropy is determined by the deformed nuclear shape, which becomes accessible experimentally through the measurement of the elliptic flow of outgoing hadrons.

    ↳ nucl-thhep-exhep-phnucl-exPRL(2020)·102 citations
22. 22*

    Double Beta Decay APPEC Committee Report

    A. Giuliani · J. J. Gomez Cadenas🇪🇸 · S. Pascoli🇬🇧 · E. Previtali🇮🇹 · R. Saakyan🇬🇧 · K. Schaeffner🇮🇹 · S. Schoenert🇩🇪

    This report constitutes the roadmap document prepared by the Double Beta Decay APPEC Committee for the APPEC SAC on the future neutrinoless double beta decay experimental programme in Europe. It reviews the existing, planned and proposed technologies for neutrinoless double beta decay, their discovery potential and technical challenges, making a critical examination of resources and schedules. It also provides a concise discussion of the theoretical issues and of the status and uncertainties on the nuclear matrix element evaluation.

    ↳ hep-exhep-phphysics.ins-det84 citations
23. 23*

    Complete Form Factors in Yang-Mills from Unitarity and Spinor Helicity in Six Dimensions

    Manuel Accettulli Huber🇬🇧 · Andreas Brandhuber🇬🇧 · Stefano De Angelis🇬🇧 · Gabriele Travaglini🇬🇧

    We present a systematic procedure to compute complete, analytic form factors of gauge-invariant operators at loop level in pure Yang-Mills. We consider applications to operators of the form $\mathrm{Tr}{F}^n$ where $F$ is the gluon field strength. Our approach is based on an extension to form factors of the dimensional reconstruction technique, in conjunction with the six-dimensional spinor-helicity formalism and generalised unitarity. For form factors this technique requires the introduction of additional scalar operators, for which we provide a systematic prescription. We also discuss a generalisation of dimensional reconstruction to any number of loops, both for amplitudes and form factors. Several novel results for one-loop minimal and non-minimal form factors of $\mathrm{Tr}{F}^n$ with $n>2$ are presented. Finally, we describe the \texttt{Mathematica} package \texttt{SpinorHelicity6D}, which is tailored to handle six-dimensional quantities written in the spinor-helicity formalism.

    ↳ hep-thhep-phPRD(2020)·17 citations
24. 24*

    Cosmological implications of electromagnetically interacting dark matter: milli-charged particles and atoms with singly and doubly charged dark matter

    Gautham A P · Shiv Sethi🇮🇳

    While the behavior of the dominant component of the dark matter is reasonably well established by cosmological observables, its particle nature and interactions with the rest of the matter are not known. We consider three dark matter models that admit electromagnetic interaction between baryons and dark matter: (a) milli-charged particle (CCDM) of charge $q_{\mathrm{ccdm}}$ and mass $m_{\mathrm{ccdm}}$, (b) a neutral atom of two charged particles of mass $m_{\mathrm{dd}}$ (DD), and (c) a neutral atom of doubly charged particle and helium nucleus (HeD). We derive and discuss in detail the formation, stability, and interaction of these atoms with baryons. We derive the implications of this new interaction in the tight-coupling approximation, which allows us to analytically gauge their impact on the matter power spectrum and CMB anisotropy. We incorporate this new interaction into the publicly-available code CLASS to obtain numerical results. We compare our results with Planck 2018 data to constrain the fraction of interacting dark matter. For the range of allowed astrophysical parameters, the HeD atom yields the results of $\Lambda$CDM model for $k<1\mathrm{Mp}{\mathrm{c}}^{-1}$, and hence its fraction is not constrained by CMB anisotropy data which is sensitive to $k<0.2\mathrm{Mp}{\mathrm{c}}^{-1}$. For $m_{\mathrm{dd}}\gtrsim 25\mathrm{GeV}$, the DD atom is also not constrained by CMB data. For $m_{\mathrm{dd}}=10\mathrm{GeV}$, the CMB data constrains the fraction of DD atoms to be smaller than 4% of the total CDM component. For $q_{\mathrm{ccdm}}=10^{-6}e$ and $m_{\mathrm{ccdm}}=50\mathrm{MeV}$, the CCDM fraction is constrained to be less than 1%.

    ↳ astro-ph.COhep-phJCAP(2020)·3 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.