Thu·Apr 28, 2022Thursday·April 28, 2022

1. 01*

   Phenomenology at the Large Hadron Collider with Deep Learning: the case of vector-like quarks decaying to light jets

   Felipe F. Freitas🇵🇹 · João Gonçalves🇵🇹 · António P. Morais🇵🇹 · Roman Pasechnik🇸🇪

   In this work, we continue our exploration of TeV-scale vector-like fermion signatures inspired by a Grand Unification scenario based on the trinification gauge group. A particular focus is given to pair-production topologies of vector-like quarks (VLQs) at the LHC, in a multi-jet plus a charged lepton and a missing energy signature. We employ Deep Learning methods and techniques based in evolutive algorithms that optimize hyper-parameters in the neural network construction, whose objective is to maximise the Asimov estimate for distinct VLQ masses. In this article, we consider the implications of an innovative approach by simultaneously combining detector images (also known as jet images) and tabular data containing kinematic information from the final states. With this technique we are able to exclude VLQs, that are specific for the considered model, to up a mass of 800 GeV in both the high-luminosity the Run-III phases of the LHC programme.

   hep-phEPJC(2022)·8 citations
2. 02*

   NNLO+PS Monte Carlo simulation of photon pair production with MiNNLOPS

   Alessandro Gavardi🇮🇹 · Carlo Oleari🇮🇹 · Emanuele Re🇮🇹

   We present a NNLO QCD accurate event generator for direct photon pair production at hadron colliders, based on the MiNNLOPS formalism, within the POWHEG BOX RES framework. Despite the presence of the photons requires the use of isolation criteria, our generator is built such that no technical cuts are needed at any stage of the event generation. Therefore, our predictions can be used to simulate kinematic distributions with arbitrary fiducial cuts. Furthermore, we describe a few modifications of the MiNNLOPS formalism in order to allow for a setting of the renormalization and factorization scales more similar to that of a fixed-order computation, thus reducing the numerical impact of higher-order terms beyond the nominal accuracy. Finally, we show several phenomenological distributions of physical interest obtained by showering the generated events with Pythia8, and we compare them with the 13 TeV data from the ATLAS Collaboration.

   hep-phJHEP(2022)·26 citations
3. 03*

   The anomalous $Wtb$ vertex and top-pair production at the LHC

   Apurba Tiwari🇮🇳 · Sudhir Kumar Gupta🇮🇳

   We perform an exclusive study of the anomalous $Wtb$ interaction in the context of LHC. The limits on $Wtb$ anomalous couplings have been estimated via the measurements of the top-quark decay width and cross-section as well as production asymmetries in case the CP is violated. Our investigations reveal that the upper bounds on $(|C_L|,|C_R|)$ would be of about (1.82, 0.03) $\times 10^{-4}$ at $2.5\sigma$ C.L., for the already collected data at the LHC with $\sqrt{S}=13$ TeV for an integrated luminosity of 139 fb${}^{-1}$. The corresponding limits for future hadron colliders, namely, High Luminosity LHC (HL-LHC), High Energy LHC (HE-LHC) and Future Circular Collider (FCC-hh) for the projected luminosities of 3 ab${}^{-1}$, 12 ab${}^{-1}$ and 30 ab${}^{-1}$ are found to be to $(0.81,0.006)\times 10^{-4}$, $(0.44,0.0017)\times 10^{-4}$ and $(0.21,0.0004)\times 10^{-4}$ respectively at 2.5$\sigma$ C. L..

   hep-phNPB(2022)·3 citations
4. 04*

   Improvements in Higgs-mass predictions with $\text{FeynHiggs}$

   Sebastian Paßehr🇩🇪

   Recent developments in the public code $\text{FeynHiggs}$ for the prediction of the Standard Model-like Higgs mass in the Minimal Supersymmetric Standard Model are presented. Improvements in the prediction based on an effective-field theory concern the cases of multi-scale hierarchies where the gluino is much heavier than the sfermions or where the additional Higgs bosons have masses between the electroweak and supersymmetry scales. The fixed-order part is improved by a re-implementation and extension of the two-loop corrections, now containing the contributions of orders $({\alpha }_t+{\alpha }_b)\cdot ({\alpha }_t+{\alpha }_b+{\alpha }_s)$ in the limit of vanishing electroweak gauge couplings for all implemented renormalization schemes. The updated version has a significantly improved numerical stability and thus an enhanced range of applicability for scenarios with heavy supersymmetric particles. All updates will be included in the upcoming version $\text{FeynHiggs-2.19.0}$.

   hep-phPoS(2022)·0 citations
5. 05*

   Explanation of the $W$ mass shift at CDF II in the Georgi-Machacek Model

   Ting-Kuo Chen🇹🇼 · Cheng-Wei Chiang🇹🇼 · Kei Yagyu🇯🇵

   The CDF II experiment has recently determined the mass of the $W$ boson to be $m_W(\text{CDF II})=80.4335\pm 0.0094$GeV, which deviates from the standard model prediction at $7\sigma$ level. Although this new result is in tension with other experiments such as those at LHC and LEP, it is worth discussing possible implications on new physics by this anomaly. We show that this large discrepancy can be explained by non-aligned vacuum expectation values of isospin triplet scalar fields in the Georgi-Machacek model extended with custodial symmetry breaking terms in the potential. The latter is required to avoid an undesirable Nambu-Goldstone boson as well as to be consistent treatment of radiative corrections. With $m_W(\text{CDF II})$ as one of the renormalization inputs at the 1-loop level, we derive the required difference in the triplet vacuum expectation values, followed by a discussion of phenomenological consequences in the scenario.

   hep-phhep-exPRD(2022)·45 citations
6. 06*

   The linear mode analysis and spin relaxation

   Jin Hu🇨🇳

   In this paper, a detailed analysis on normal modes of the linearized Hermite collision operator is presented, which follows from linearizing spin Boltzmann equation for massive fermions proposed in \cite{Weickgenannt:2021cuo} with the non-diagonal part of the transition rate neglected and approximating what we got with a mutilated operator. With the assumption of total angular momentum conservation, the collision term is proved to well describe the equilibrium state and gives proper interpretation for collisional invariants, thus is relevant for the research on local spin polarization. Following the familiar fashion as used in quantum mechanics, we treat the problem of solving normal modes as a degenerate perturbation problem and calculate the dispersion relations for intriguing eleven zero modes, which form one-to-one correspondence to all collisional invariants. We find that the results of spinless modes appearing in ordinary hydrodynamics are consistent with available conclusions in textbooks. As for spin-related modes, we obtain the frequencies up to second order in wave vector and relate them with the dissipation of spin density fluctuation. In addition, the ratio of two relaxation time scales for spin and momentum is shown as a function of reduced mass, which reads that based on present framework spin equilibration is almost as slow as momentum equilibration as far as the strange quark spins in quark gluon plasma (QGP) are concerned.

   hep-phnucl-thPRD(2022)·16 citations
7. 07*

   The CDF W-mass, muon g-2, and dark matter in a $U(1{)}_{L_{\mu }-L_{\tau }}$ model with vector-like leptons

   Quan Zhou · Xiao-Fang Han

   We study the CDF $W$-mass, muon $g-2$, and dark matter observables in a local $U(1{)}_{L_{\mu }-L_{\tau }}$ model in which the new particles include three vector-like leptons ($E_1,E_2,N$), a new gauge boson $Z^{\prime }$, a scalar $S$ (breaking $U(1{)}_{L_{\mu }-L_{\tau }}$), a scalar dark matter $X_I$ and its partner $X_R$. We find that the CDF $W$-mass disfavors $m_{E_1}=m_{E_2}=m_N$ or $s_L=s_R=0$ where $s_{L(R)}$ is mixing parameter of left (right)-handed fields of vector-like leptons. A large mass splitting between $E_1$ and $E_2$ is favored when the differences between $s_L$ and $s_R$ becomes small. The muon $g-2$ anomaly can be simultaneously explained for appropriate difference between $s_L$ $(m_{E_1})$ and $s_R$ $(m_{E_2})$, and some regions are excluded by the diphoton signal data of the 125 GeV Higgs. Combined with the CDF $W$-mass, muon $g-2$ anomaly and other relevant constraints, the correct dark matter relic density is mainly obtained in two different scenarios: (i) $X_I{X}_I\to Z^{\prime }{Z}^{\prime },SS$ for $m_{Z^{\prime }}(m_S)<m_{X_I}$ and (ii) the co-annihilation processes for $min(m_{E_1},m_{E_2},m_N,m_{X_R})$ closed to $m_{X_I}$. Finally, we use the direct searches for $2\ell +E_T^{miss}$ event at the LHC to constrain the model, and show the allowed mass ranges of the vector-like leptons and dark matter.

   hep-phEPJC(2022)·36 citations
8. 08*

   SMEFT predictions for $gg\to hh$ at full NLO QCD and truncation uncertainties

   Gudrun Heinrich🇩🇪 · Jannis Lang🇩🇪 · Ludovic Scyboz🇬🇧

   We present a calculation of the NLO QCD corrections for Higgs-boson pair production in gluon fusion including effects of anomalous couplings within Standard Model Effective Field Theory (SMEFT). We study effects of different truncation options of the EFT expansion in $1/\Lambda$ and of double operator insertions, both at total cross-section level as well as for the distribution of the invariant mass of the Higgs-boson pair, at $\sqrt{s}=13$ TeV. The NLO corrections are implemented in the generator \texttt{ggHH_SMEFT} in the $\text{Powheg-Box-V2}$ framework.

   hep-phJHEP(2022)·78 citations
9. 09*

   Newly observed $a_0(1817)$ as the scaling point of constructing the scalar meson spectroscopy

   Dan Guo🇨🇳 · Wei Chen🇨🇳 · Hua-Xing Chen🇨🇳 · Xiang Liu🇨🇳 · Shi-Lin Zhu🇨🇳

   Stimulated by the newly observed $a_0(1817)$ by the BESIII Collaboration, we find a perfect Regge trajectory composed of the $a_0(980)$, $a_0(1450)$, and $a_0(1817)$, which leads us to categorize the $a_0(980)$, $a_0(1450)$, and $a_0(1817)$ into the isovector scalar meson family. This scenario is supported by their two-body Okubo-Zweig-Iizuka allowed strong decay behaviors. In this scheme, we also predict the third radial excitation of the $a_0(980)$, which is denoted as the $a_0(2115)$, accessible at future experiment as a direct test of this assignment. We find another Regge trajectory which contains three isoscalar scalar states $f_0(980)$, $X(1812)$, and $f_0(2100)$. We investigate their two-body Okubo-Zweig-Iizuka allowed strong decay patterns, which are roughly consistent with the experimental data. The $f_0(980)$, $X(1812)$, and $f_0(2100)$ can be well grouped into the isoscalar scalar meson family. We want to emphasize that these two Regge trajectories have a similar slope. In summary, the present work provides a scheme of constructing the scalar meson family based on these reported scalar states. The possibility of the $f_0(1710)$ as the candidate of the scalar glueball cannot be excluded by the observation of the $a_0(1817)$ since the $a_0(1817)$ is more suitable as the isovector partner of the $X(1812)$.

   hep-phhep-exhep-latPRD(2022)·30 citations
10. 10*

    First principles determination of bubble wall velocity

    Benoit Laurent🇨🇦 · James M. Cline🇨🇦

    The terminal wall velocity of a first-order phase transition bubble can be calculated from a set of fluid equations describing the scalar fields and the plasma's state. We rederive these equations from the energy-momentum tensor conservation and the Boltzmann equation, without linearizing in the background temperature and fluid velocity. The resulting equations have a finite solution for any wall velocity. We propose a spectral method to integrate the Boltzmann equation, which is simple, efficient and accurate. As an example, we apply this new methodology to the singlet scalar extension of the standard model. We find that all solutions are naturally categorized as deflagrations ($v_w\sim c_s$) or ultrarelativistic detonations (${\gamma }_w\gtrsim 10$). Furthermore, the contributions from out-of-equilibrium effects are, most of the time, subdominant. Finally, we use these results to propose several approximation schemes with increasing levels of complexity and accuracy. They can be used to considerably simplify the methodology while correctly describing the qualitative behavior of the bubble wall.

    hep-phastro-ph.COPRD(2022)·168 citations
11. 11*

    Moments for positivity: using Drell-Yan data to test positivity bounds and reverse-engineer new physics

    Xu Li🇨🇳 · Ken Mimasu🇬🇧 · Kimiko Yamashita🇰🇷 · Chengjie Yang🇨🇳 · Cen Zhang🇨🇳 · Shuang-Yong Zhou🇨🇳

    Moments of the leptonic angular distribution in the Drell-Yan process have recently been shown to be sensitive probes of a specific class of dimension-8, four-fermion operators in the Standard Model Effective Field Theory, involving a pair of quarks and leptons. The same operators are also subject to positivity bounds, when requiring the associated (unknown) UV completion to obey basic principles of quantum field theory. We perform a phenomenological study to quantify the sensitivity of the high-luminosity LHC to this set of operators and, by extension, the positivity bounds. We further extend the angular basis of moments and consider double differential information to improve the ability to disentangle the different operators, leading to a sensitivity to new physics scales up to 3 TeV. We use this information to explore the violation of positivity at the LHC as a way to test the underlying principles of quantum field theory. Finally, we present a case study which combines our results with information from other (current and prospective) experiments, as well as the positivity cone to infer the properties of possible tree-level UV completions. The data lead to robust, model-independent lower bounds on the $M/\sqrt{g}$ combination of the particle mass and coupling, for states that couple to right-handed leptons and/or up quarks.

    hep-phhep-exJHEP(2022)·48 citations
12. 12*

    Unitarity bounds for all symmetry-constrained 3HDMs

    Miguel P. Bento🇵🇹 · Jorge C. Romão🇵🇹 · João P. Silva🇵🇹

    Models with three Higgs doublets (3HDM) are the source of much recent activity, for they are key components of many solutions to the problems of the Standard Model; from extra sources of CP violation to Dark Matter candidates. We compute explicitly the theoretical bounds for all symmetry-constrained 3HDM arising from the perturbative unitarity of two-to-two scattering amplitudes. In addition, we propose a method based on principal minors that foregoes diagonalization and which is preferable in all models (not only 3HDM) dealing with large scattering matrices.

    hep-phJHEP(2022)·40 citations
13. 13*

    ADM formulation and Hamiltonian analysis of $f(Q)$ gravity

    Kun Hu🇨🇳 · Taishi Katsuragawa🇨🇳 · Taotao Qiu🇨🇳

    $f(Q)$ gravity is an extension of the symmetric teleparallel equivalent to general relativity. We demonstrate the Hamiltonian analysis of $f(Q)$ gravity with fixing the coincident gauge condition. Using the standard Dirac-Bergmann algorithm, we show that $f(Q)$ gravity has 8 physical degrees of freedom. This result reflects that the diffeomorphism symmetry of $f(Q)$ gravity is completely broken due to the gauge fixing. Moreover, in terms of the perturbations, we discuss the possible mode decomposition of these degrees of freedom.

    ↳ gr-qcastro-ph.COhep-phhep-thPRD(2022)·81 citations
14. 14*

    (P)reheating and gravitational waves in $\alpha$-attractor models

    Tomasz Krajewski🇵🇱 · Krzysztof Turzyński🇵🇱

    We study post-inflationary evolution in $\alpha$-attractor T-models of inflation. We consider the dynamics of both scalar fields present in these models: the inflaton and the spectator, as a negative field-space curvature may lead to geometrical destabilization of the spectator. We perform state-of-the-art lattice simulations with a dedicated numerical code optimized for those models. We corroborate earlier findings that the perturbations of the spectator field are much more unstable than the perturbations of the inflaton field, so the dynamics of early stages of preheating is dominated by the evolution of spectator perturbations. We also calculate the spectrum of gravitational waves originating from scalar fluctuations in order to determine if the $\alpha$-attractor T-models can be constrained or even ruled out by present cosmological observations, but not by direct searches of gravitational waves.

    ↳ astro-ph.COgr-qchep-phJCAP(2022)·16 citations
15. 15*

    Ab initio studies of double Gamow-Teller transition and its correlation with neutrinoless double beta decay

    J. M. Yao🇨🇳 · I. Ginnett🇨🇦 · A. Belley🇨🇦 · T. Miyagi🇩🇪 · R. Wirth🇺🇸 · S. Bogner🇺🇸 · J. Engel🇺🇸 · H. Hergert🇺🇸 · J. D. Holt🇨🇦 · S. R. Stroberg🇺🇸

    We use chiral interactions and several {\em ab initio} methods to compute the nuclear matrix elements (NMEs) for ground-state to ground-state double Gamow-Teller transitions in a range of isotopes, and explore the correlation of these NMEs with those for neutrinoless double beta decay produced by the exchange of a light Majorana neutrino. When all the NMEs of both isospin-conserving and isospin-changing transitions from the {\em ab initio} calculations are considered, the correlation is strong. For the experimentally relevant isospin-changing transitions by themselves, however, the correlation is weaker and may not be helpful for reducing the uncertainty in the NMEs for neutrinoless double-beta decay.

    ↳ nucl-thhep-phnucl-exPRC(2022)·28 citations
16. 16*

    Requirements on Quantum Superpositions of Macro-Objects for Sensing Neutrinos

    Eva Kilian🇬🇧 · Marko Toroš🇬🇧 · Frank F. Deppisch🇬🇧 · Ruben Saakyan🇬🇧 · Sougato Bose🇬🇧

    We examine a macroscopic system in a quantum superposition of two spatially separated localized states as a detector for a stream of weakly interacting relativistic particles. We do this using the explicit example of neutrinos with MeV-scale energy scattering from a solid object via neutral-current neutrino-nucleus scattering. Presuming the (anti-)neutrino source to be a nuclear fission reactor, we utilize the estimated flux and coherent elastic neutrino-nucleus cross section to constrain the spatial separation $\Delta$x and describe the temporal evolution of the sensing system. Particularly, we find that a potentially measurable relative phase between quantum superposed components is obtained for a single gram scale mass placed in a superposition of spatial components separated by $10^{-14}$m under sufficient cooling and background suppression.

    ↳ quant-phhep-exhep-phhep-thPRResearch(2023)·14 citations
17. 17*

    Gauge invariance from on-shell massive amplitudes and tree unitarity

    Da Liu🇺🇸 · Zhewei Yin🇺🇸

    We study the three-particle and four-particle scattering amplitudes for an arbitrary, finite number of massive scalars, spinors and vectors by employing the on-shell massive spinor formalism. We consider the most general three-particle amplitudes with energy growing behavior at most of $\mathcal{O}(E)$. This is the special case of the requirement of tree unitarity, which states that the $N$-particle scattering amplitudes at tree-level should grow at most as $\mathcal{O}(E^{4-N})$ in the high energy hard scattering limit, i.e. at fixed non-zero angles. Then the factorizable parts of the four-particle amplitudes are calculated by gluing the on-shell three-particle amplitudes together and utilizing the fact that tree-level amplitudes have only simple poles. The contact parts of the four-particle amplitudes are further determined by tree unitarity, which also puts strong constraints on the possible allowed three-particle coupling constants and the masses. The derived relations among them converge to the predictions of gauge invariance in the UV theory. This provides a purely on-shell understanding of spontaneously broken gauge theories.

    ↳ hep-thhep-phPRD(2022)·27 citations
18. 18*

    Cosmic strings from pure Yang-Mills theory

    Masaki Yamada🇯🇵 · Kazuya Yonekura🇯🇵

    We discuss the formation of cosmic strings or macroscopic color flux tubes at the phase transition from the deconfinement to confinement phase in pure Yang-Mills (YM) theory, such as SU($N$), Sp($N$), SO($N$), and Spin($N$), based on the current understanding of theoretical physics. According to the holographic dual descriptions, the cosmic strings are dual to fundamental strings or wrapped D-branes in the gravity side depending on the structure of the gauge group, and the reconnection probability is suppressed by $\mathcal{O}(N^{-2})$ and $e^{-\mathcal{O}(N)}$, respectively. The pure YM theory thus provides a simple realization of cosmic F- and D-strings without the need for a brane-inflationary scenario or extra dimension. We also review the stability of cosmic strings based on the concept of 1-form symmetry, which further implies the existence of a baryon vertex in some YM theory. We calculate the gravitational wave spectrum that is emitted from the cosmic strings based on an extended velocity-dependent one-scale model and discuss its detectability based on ongoing and planned gravitational-wave experiments. In particular, the SKA and LISA can observe gravitational signals if the confinement scale is higher than $\mathcal{O}(10^{12})\mathrm{GeV}$ and $\mathcal{O}(10^{10})\mathrm{GeV}$ for SU($N$) with $N=\mathcal{O}(1)$, respectively.

    ↳ hep-thastro-ph.COhep-phPRD(2022)·44 citations
19. 19*

    A Quantum-Mechanical Mechanism for Reducing the Cosmological Constant

    Nemanja Kaloper🇺🇸 · Alexander Westphal🇩🇪

    We exhibit a mechanism which dynamically adjusts cosmological constant toward $0^{+}$. The adjustment is quantum-mechanical, discharging cosmological constant in random discrete steps. It renders de Sitter space unstable, and triggers its decay toward Minkowski. Since the instability dynamically stops at $\Lambda =0$, the evolution favors the terminal Minkowski space without a need for anthropics. The mechanism works for any QFT coupled to gravity.

    ↳ hep-thastro-ph.COgr-qchep-phPRD(2022)·22 citations
20. 20*

    Cosmic F- and D-strings from pure Yang-Mills theory

    Masaki Yamada🇯🇵 · Kazuya Yonekura🇯🇵

    We discuss the formation of cosmic strings or macroscopic color flux tubes after the deconfinement/confinement phase transition in the pure Yang-Mills theory. Based on holographic dual descriptions, these cosmic strings can be interpreted as fundamental (F-) strings or wrapped D-branes (which we call as D-strings) in the gravity side, depending on the structure of the gauge group. In fact, the reconnection probabilities of the F- and D-strings are suppressed by factors of $1/N^2$ and $e^{-cN}$, where $c=\mathcal{O}(1)$, in a large-$N$ limit, respectively. Supported by the picture of electric-magnetic duality, we discuss that color flux tubes form after the deconfinement/confinement phase transition, just like the formation of local cosmic strings after spontaneous symmetry breaking in the weak-U(1) gauge theory. We use an extended velocity-dependent one-scale model to describe the dynamics of the string network and calculate the gravitational wave signals from string loops. We also discuss the dependence on the size of produced string loops.

    ↳ hep-thastro-ph.COhep-phPLB(2023)·36 citations
21. 21*

    La Antimateria

    Beatriz Gato-Rivera🇪🇸

    Antimatter is one of the most fascinating aspects of Particle Physics and one of the most unknown ones too. In this article we concisely explain what is antimatter and its distinction between primordial and secondary, how it is produced, where it can be found, the experiments carried out at CERN to create and analyze antiatoms, the problem of the matter-antimatter asymmetry, and the medical and technological applications of antimatter in our society. -- La antimateria es uno de los aspectos más fascinantes de la Física de Partículas, y también uno de los más desconocidos. En este artículo explicamos concisamente qué es la antimateria y su diferenciación entre primordial y secundaria, cómo se produce, donde se encuentra, los experimentos que se realizan en el CERN para crear y analizar antiátomos, el problema de la asimetría materia-antimateria, y las aplicaciones médicas y tecnológicas de la antimateria en nuestra sociedad.

    ↳ physics.pop-phhep-exhep-phhep-thRevista Espa\~nola de F\'isica, Vol. 34, …·0 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.