Mon·Aug 26, 2019Monday·August 26, 2019

1. 01*

   Two-real-scalar-singlet extension of the SM: LHC phenomenology and benchmark scenarios

   Tania Robens🇭🇷 · Tim Stefaniak🇩🇪 · Jonas Wittbrodt🇩🇪

   We investigate the LHC phenomenology of a model where the Standard Model (SM) scalar sector is extended by two real scalar singlets. A ${\mathbb{Z}}_2\otimes {\mathbb{Z}}_2^{\prime }$ discrete symmetry is imposed to reduce the number of scalar potential parameters, which is spontaneously broken by the vacuum expectation values of the singlet fields. As a result, all three neutral scalar fields mix, leading to three neutral CP-even scalar bosons, out of which one is identified with the observed Higgs boson at 125 GeV. We explore all relevant collider signatures of the three scalars in this model. Besides the single production of a scalar boson decaying directly to SM particle final states, we extensively discuss the possibility of resonant multi-scalar production. The latter includes decays of the produced scalar boson to two identical scalars ("symmetric decays"), as well as to two different scalars ("asymmetric decays"). Furthermore, we discuss the possibility of successive decays to the lightest scalar states ("cascade decays"), which lead to experimentally spectacular three- and four-Higgs final states. We provide six benchmark scenarios for detailed experimental studies of these Higgs-to-Higgs decay signatures.

   hep-phhep-exEPJC(2020)·167 citations
2. 02*

   Neutral Current Neutrino-Nucleus Scattering. Theory

   Carlotta Giusti🇮🇹 · Martin V. Ivanov🇧🇬

   The treatment of nuclear effects in neutrino-nucleus interactions is one of the main sources of systematic uncertainty for the analysis and interpretation of data of neutrino oscillation experiments. Neutrinos interact with nuclei via charged or neutral currents and both cases must be studied to obtain a complete information. We give an overview of the theoretical work that has been done to describe nuclear effects in neutral-current neutrin onucleus scattering in the kinematic region ranging between beam energies of a few hundreds MeV to a few GeV, which is typical of most ongoing and future accelerator-based neutrino experiments, and where quasielastic scattering is the main interaction mechanism. We review the current status and challenges of the theoretical models, the role and relevance of the contributions of different nuclear effects, and the present status of the comparison between the numerical predictions of the models as well as the available experimental data. We discuss also the sensitivity to the strange form factors of the nucleon and the methods and observables that can allow one to obtain evidence for a possible strange quark contribution from measurements of neutrino and antineutrino-nucleus scattering.

   hep-phnucl-exnucl-thJ.Phys.G(2020)·18 citations
3. 03*

   Resolving the $(g-2{)}_{\mu }$ and $B$ anomalies with leptoquarks and a dark Higgs boson

   Alakabha Datta🇺🇸 · Jonathan L. Feng🇺🇸 · Saeed Kamali🇺🇸 · Jacky Kumar🇨🇦

   At present, there are outstanding discrepancies between standard model predictions and measurements of the muon's $g-2$ and several $B$-meson properties. We resolve these anomalies by considering a two-Higgs-doublet model extended to include leptoquarks and a dark Higgs boson $S$. The leptoquarks modify $B$-meson decays and also induce an $S\gamma \gamma$ coupling, which contributes to the muon's $g-2$ through a Barr-Zee diagram. We show that, for TeV-scale leptoquarks and dark Higgs boson masses $m_S\sim 10-200\text{MeV}$, a consistent resolution to all of the anomalies exists. The model predicts interesting new decays, such as $B\to K^{(\ast )}{e}^{+}{e}^{-}$, $B\to K^{(\ast )}\gamma \gamma$, $K\to \pi \gamma \gamma$, and $h\to \gamma \gamma \gamma \gamma$, with branching fractions not far below current bounds.

   hep-phhep-exPRD(2020)·36 citations
4. 04*

   Transverse momentum dependent parton distributions of pion in the light-front holographic model

   Navdeep Kaur🇮🇳 · Harleen Dahiya🇮🇳

   Using the light-front holographic model, we study the transverse momentum dependent parton distributions (TMDs) for the case of pion. At leading twist, the unpolarized parton distribution function $f_{1\pi }(x,{\text{bfk}}^2)$ and the Boer-Mulders function $h_{1\pi }^{\perp }(x,{\text{bfk}}^2)$ are obtained for pion. We calculate both the functions using the light-front holographic model with spin improved wave function and compare the predicted results with available results of other models. In order to provide inputs in predicting future experimental data, a LO evolution is performed from model scale to experimental scale for the case of unpolarized parton distribution function $f_{1\pi }(x,{\text{bfk}}^2)$.

   hep-phInt.J.Mod.Phys.A(2021)·11 citations
5. 05*

   Nambu-Jona-Lasinio model in a sphere

   Zheng Zhang🇨🇳 · Chao Shi🇨🇳 · Hongshi Zong🇨🇳

   We study the chiral phase transition of the two flavor Nambu-Jona-Lasinio (NJL) model in a sphere with the MIT boundary condition. We find that the MIT boundary condition results in much stronger finite size effects than the antiperiodic boundary condition. Our work may be helpful to study the finite size effects in heavy-ion collision in a more realistic way.

   hep-phnucl-thPRD(2020)·14 citations
6. 06*

   Stochastic inflation with an extremely large number of $e$-folds

   Naoya Kitajima🇯🇵 · Yuichiro Tada🇯🇵 · Fuminobu Takahashi🇯🇵

   We propose a class of single-field, slow-roll inflation models in which a typical number of $e$-folds can be extremely large. The key point is to introduce a very shallow local minimum near the top of the potential in a hilltop inflation model. In particular, a typical number of $e$-folds is enhanced if classical behavior dominates around the local minimum such that the inflaton probability distribution is drifted to the local minimum as a whole. After the inflaton escapes from the local minimum due to the stochastic dynamics, the ordinary slow-roll inflation follows and it can generate the primordial density perturbation consistent with observation. Interestingly, our scenario inherits the advantages of the old and new inflation: the typical $e$-folds can be extremely large as in the old inflation, and slow-roll inflation naturally follows after the stochastic regime as in the new inflation. In our numerical example, the typical number of $e$-folds can be as large as $10^{10^{10}}$, which is large enough for various light scalars such the QCD axion to reach the Bunch-Davies distribution.

   hep-phastro-ph.COPLB(2020)·23 citations
7. 07*

   Perturbative static quark potential in Maximal Abelian gauge

   Matthias Berwein🇯🇵 · Yukinari Sumino🇯🇵

   We calculate the static quark potential for an SU(N) gauge theory in the Maximal Abelian gauge as well as its Abelian projection up to two loops in perturbation theory. We discuss its renormalization properties. The result is compared with a recent lattice result at $r\lesssim 0.5$ fm.

   hep-phhep-lathep-thPLB(2019)·0 citations
8. 08*

   Heavy hadronic molecules with pion exchange and quark core couplings: a guide for practitioners

   Yasuhiro Yamaguchi🇯🇵 · Atsushi Hosaka🇯🇵 · Sachiko Takeuchi🇯🇵 · Makoto Takizawa🇯🇵

   We discuss selected and important features of hadronic molecules as one of promising forms of exotic hadrons near thresholds. Using examples of $D{\bar{D}}^{\ast }$ systems such as $X(3872)$ and $Z_c$, emphasis is put on the roles of the one pion exchange interaction between them and their coupling to intrinsic quark states. Thus hadronic molecules emerge as admixtures of the dominant long-range hadron structure and short-range quark structure. For the pion exchange interaction, properties of the tensor force are analyzed in detail. More coupled channels supply more attractions, and heavier constituents suppress kinetic energies, providing more chances to form hadronic molecules of heavy hadrons. Throughout this article, we show details of basic ideas and methods.

   hep-phnucl-thJ.Phys.G(2020)·110 citations
9. 09*

   Semirelativistic Bound States: (Pseudo-) Spinless-Salpeter Approaches Reassessed

   Wolfgang Lucha🇦🇹

   Relativistic quantum field theory offers, in form of the homogeneous Bethe-Salpeter framework, a (Poincaré-covariant) description of bound states in terms of their underlying theory's fundamental degrees of freedom. In view of the intrinsic complexity of this approach, simplifications have been sought and abundantly found. The significance of these latter approximations may be estimated by comparing their predictions with (easily inferable) rigorous constraints on the bound-state spectra, such as existence, number and location of discrete eigenstates. The application of these techniques to selected proposed bound-state equations is exemplified for a large class of generalizations of the Hellmann potential frequently employed in several areas of science such as physics and chemistry.

   hep-phnucl-thPoS(2020)·1 citation
10. 10*

    Flavour-Exotic Tetraquarks in Large-$N_{\mathrm{c}}$ QCD: Do They Exist?

    Wolfgang Lucha🇦🇹 · Dmitri Melikhov🇦🇹 · Hagop Sazdjian🇫🇷

    Flavour-exotic tetraquark mesons, by definition bound states of two quarks and two antiquarks of four mutually different quark flavours, are, for given Lorentz features, subject to two incompatible constraints: On the one hand, within quantum chromodynamics a formation of compact tetraquark states is most easily envisaged by merging two colour-antisymmetric two-quark clusters, a diquark and an antidiquark. This path, however, leads to merely a single tetraquark state of chosen Lorentz characteristics. On the other hand, in the limit of the number of colour degrees of freedom growing beyond bounds, internal consistency at leading order calls for the presence of (at least) two of such tetraquark states of identical quark-flavour composition. The failure of attempts to reconcile these two contradictory insights suggests the nonexistence of compact flavour-exotic tetraquark mesons.

    hep-phPoS(2020)·0 citations
11. 11*

    Tetraquark-Adequate QCD Sum Rules

    Wolfgang Lucha🇦🇹 · Dmitri Melikhov🇦🇹 · Hagop Sazdjian🇫🇷

    With the experimental observation of several credible candidates for multiquark hadrons, the latter states re-entered the focus of interest of theoretical strong-interaction physics. Proper treatment of hadronic bound states by quantum chromodynamics, QCD, the quantum field theory governing all strong interactions, necessitates a nonperturbative approach. A well-established framework of this kind is provided by QCD sum rules relating hadron features to the parameters of QCD. Conceptual reconsideration, however, reveals that, in order to really match the peculiarities of multiquarks, the long-standing conventional QCD sum-rule techniques evidently must be subjected to considerable modification. The so far overlooked necessity for such adaptations is most easily demonstrated for the case of least complexity, that is, for tetraquarks, bound states of two quarks and two antiquarks.

    hep-phPoS(2020)·2 citations
12. 12*

    Exploring anomalous couplings in Higgs boson pair production through shape analysis

    Matteo Capozi🇩🇪 · Gudrun Heinrich🇩🇪

    We classify shapes of Higgs boson pair invariant mass distributions $m_{hh}$, calculated at NLO with full top quark mass dependence, and visualise how distinct classes of shapes relate to the underlying coupling parameter space. Our study is based on a five-dimensional parameter space relevant for Higgs boson pair production in a non-linear Effective Field Theory framework. We use two approaches: an analysis based on predefined shape types and a classification into shape clusters based on unsupervised learning. We find that our method based on unsupervised learning is able to capture shape features very well and therefore allows a more detailed study of the impact of anomalous couplings on the $m_{hh}$ shape compared to more conventional approaches to a shape analysis.

    hep-phJHEP(2020)·75 citations
13. 13*

    Quantum Algorithms for Jet Clustering

    Annie Y. Wei🇺🇸 · Preksha Naik🇺🇸 · Aram W. Harrow🇺🇸 · Jesse Thaler🇺🇸

    Identifying jets formed in high-energy particle collisions requires solving optimization problems over potentially large numbers of final-state particles. In this work, we consider the possibility of using quantum computers to speed up jet clustering algorithms. Focusing on the case of electron-positron collisions, we consider a well-known event shape called thrust whose optimum corresponds to the most jet-like separating plane among a set of particles, thereby defining two hemisphere jets. We show how to formulate thrust both as a quantum annealing problem and as a Grover search problem. A key component of our analysis is the consideration of realistic models for interfacing classical data with a quantum algorithm. With a sequential computing model, we show how to speed up the well-known O(N^3) classical algorithm to an O(N^2) quantum algorithm, including the O(N) overhead of loading classical data from N final-state particles. Along the way, we also identify a way to speed up the classical algorithm to O(N^2 log N) using a sorting strategy inspired by the SISCone jet algorithm, which has no natural quantum counterpart. With a parallel computing model, we achieve O(N log N) scaling in both the classical and quantum cases. Finally, we consider the generalization of these quantum methods to other jet algorithms more closely related to those used for proton-proton collisions at the Large Hadron Collider.

    hep-phquant-phPRD(2020)·81 citations
14. 14*

    Mass Agnostic Jet Taggers

    Layne Bradshaw🇺🇸 · Rashmish K. Mishra🇮🇹 · Andrea Mitridate🇮🇹 · Bryan Ostdiek🇺🇸

    Searching for new physics in large data sets needs a balance between two competing effects---signal identification vs background distortion. In this work, we perform a systematic study of both single variable and multivariate jet tagging methods that aim for this balance. The methods preserve the shape of the background distribution by either augmenting the training procedure or the data itself. Multiple quantitative metrics to compare the methods are considered, for tagging 2-, 3-, or 4-prong jets from the QCD background. This is the first study to show that the data augmentation techniques of Planing and PCA based scaling deliver similar performance as the augmented training techniques of Adversarial NN and uBoost, but are both easier to implement and computationally cheaper.

    hep-phhep-exSciPost Phys.(2020)·57 citations
15. 15*

    Positivity in the effective field theory of cosmological perturbations

    Gen Ye🇨🇳 · Yun-Song Piao🇨🇳

    Requiring the existence of a unitary, causal and local UV-completion places a set of positivity bounds on the corresponding effective field theories (EFTs). We discuss the obstructions and possibility in applying the positivity bound to cosmology, in particular the EFT of cosmological perturbations. Taking a $c_T=1$ beyond-Horndeski EFT as an illustrative example, we derive such bounds, which incorporate the cosmological correction of order $H^2/{\Lambda }^2$, $\Lambda$ being the cutoff scale. The derived bounds are applied to slow-roll inflation with beyond Horndeski operators. It is found that the cosmological positivity bounds may be either stronger or weaker than their flat space counterpart.

    ↳ hep-thastro-ph.COgr-qchep-phEPJC(2020)·32 citations
16. 16*

    A mechanism for formation of Bose-Einstein condensation in cosmology

    Recai Erdem🇹🇷 · Kemal Gültekin🇹🇷

    We introduce a toy model of scalar particles with a trilinear scalar coupling in cosmology. The trilinear coupling ${\varphi }^2\chi$ causes production of non-relativistic $\varphi$ particles through the process $\chi \chi \to \varphi \varphi$ where, initially, only relativistic $\chi$ particles are present. We consider the initial times of $\chi \chi \to \varphi \varphi$ and observe that the curved space effects promote formation of Bose-Einstein condensate of $\varphi$ particles.

    ↳ gr-qcastro-ph.COhep-phhep-thJCAP(2019)·8 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.