HEP Phenomenology·hep-ph
30 papers—22 primary·8 cross-listed·reconstructed*
V.G. Ksenzov🇷🇺 · A.I. Romanov🇷🇺
We study two-dimensional model with a fermion field and a self-interaction scalar field with the Yukawa interaction beyond the framework of the one-loop approximation. We show that in the model besides a phase transitions appear decays of the excited scalar states.
The XYZ mesons are mesons that contain a heavy quark and antiquark but have properties that seem to require additional constituents. Some of them are electrically charged, so they must be tetraquark mesons whose additional constituents are a light quark and antiquark. The list of XYZ mesons has grown to about two dozen over the last decade. A promising approach to understanding these mesons within QCD is the Born-Oppenheimer approximation, which reduces the problem to the solution of the Schrodinger equation in potentials that can be calculated using lattice QCD. The Born-Oppenheimer approximation has not yet revealed the pattern of the XYZ mesons, but it provides a compelling framework for understanding them from the fundamental theory.
Haiying Cai🇫🇷 · Thomas Flacke🇰🇷 · Mickael Lespinasse🇫🇷
We study the light scalar resonance sector of a composite Higgs model UV embedding based on the coset . Beyond the Higgs multiplet, the pseudo Nambu-Goldstone sector of this model contains Standard Model singlets which couple to the Standard Model gauge bosons through Wess-Zumino-Witten anomaly terms. They can thus be produced in gluon fusion and decay into either gluons or pairs of electroweak gauge bosons , , , or . In this letter we show that one of the pseudo Nambu-Goldstone boson states has appropriate couplings in order to explain a di-boson excess in the channel whilst not being excluded by LHC run I bounds on the di-jet, and decay channels. A di-boson resonance production cross section of 10 fb at LHC run I is not a prediction of the model, but can be obtained if the confining gauge group is of high rank.
Yonit Hochberg🇺🇸 · Matt Pyle🇺🇸 · Yue Zhao🇺🇸 · Kathryn M. Zurek🇺🇸
We examine in greater detail the recent proposal of using superconductors for detecting dark matter as light as the warm dark matter limit of O(keV). Detection of such light dark matter is possible if the entire kinetic energy of the dark matter is extracted in the scattering, and if the experiment is sensitive to O(meV) energy depositions. This is the case for Fermi-degenerate materials in which the Fermi velocity exceeds the dark matter velocity dispersion in the Milky Way of ~10^-3. We focus on a concrete experimental proposal using a superconducting target with a transition edge sensor in order to detect the small energy deposits from the dark matter scatterings. Considering a wide variety of constraints, from dark matter self-interactions to the cosmic microwave background, we show that models consistent with cosmological/astrophysical and terrestrial constraints are observable with such detectors. A wider range of viable models with dark matter mass below an MeV is available if dark matter or mediator properties (such as couplings or masses) differ at BBN epoch or in stellar interiors from those in superconductors. We also show that metal targets pay a strong in-medium suppression for kinetically mixed mediators; this suppression is alleviated with insulating targets.
Eric Kuflik🇺🇸 · Maxim Perelstein🇺🇸 · Nicolas Rey-Le Lorier🇺🇸 · Yu-Dai Tsai🇺🇸
We present a novel dark matter candidate, an Elastically Decoupling Relic (ELDER), which is a cold thermal relic whose present abundance is determined by the cross-section of its elastic scattering on Standard Model particles. The dark matter candidate is predicted to have a mass ranging from a few to a few hundred MeV, and an elastic scattering cross-section with electrons, photons and/or neutrinos in the fb range.
Benjamín Grinstein🇺🇸 · Christopher W. Murphy🇮🇹 · Patipan Uttayarat🇹🇭
We compute all of the one-loop corrections that are enhanced, , in the limit , to all the longitudinal vector boson and Higgs boson scattering amplitudes in the -conserving two-Higgs doublet model with a softly broken symmetry. In the two simplified scenarios we study, the typical bound we find is .
The observation of many unexpected states decaying into heavy quarkonia has challenged the usual QQbar interpretation. One of the most studied exotic states, the X(3872), happens to be copiously produced in high-energy hadron collisions. We discuss how this large prompt production cross-section disfavors a loosely-bound molecule interpretation for this particle. This is supported by Monte Carlo simulations, and by a comparison with extrapolated light nuclei data by ALICE.
Edgar V. Bugaev🇷🇺 · Boris V. Mangazeev🇷🇺
Nuclear shadowing corrections to the structure functions of deep inelastic scattering of intermediate-mass nuclei are calculated at very low values of Bjorken x and small values of Q^2 (Q^2<5 GeV^2). The two-component approach (generalized VMD plus hard pomeron) is used for a description of the underlying virtual photon - nucleon interaction. The hard component of the nucleon structure function is calculated in a framework of the colour dipole model with dipole cross section having Regge-type energy dependence. Numerical results for nuclear shadowing corrections are compared with available data of E665 and NMC collaborations.
Suchismita Sahoo🇮🇳 · Rukmani Mohanta🇮🇳
We study the effect of scalar leptoquarks in the lepton flavour violating meson decays induced by the flavour changing transitions with . In the standard model these transitions are extremely rare as they are either two-loop suppressed or proceed via box diagrams with tiny neutrino masses in the loop. However, in the leptoquark model they can occur at tree level and are expected to have significantly large branching ratios. The leptoquark parameter space is constrained using the experimental limits on the branching ratios of processes. Using such constrained parameter space, we predict the branching ratios of LFV semileptonic meson decays, such as , and , which are found to be within the experimental reach of LHCb and the upcoming Belle II experiments. We also investigate the rare leptonic and decays in the leptoquark model.
Vein S Kong🇺🇸 · Jiakun Li · Yujia Zhang🇨🇳
In the Large Hardron Collider (LHC), multiple proton-proton collisions cause pileup in reconstructing energy information for a single primary collision (jet). This project aims to select the most important features and create a model to accurately estimate jet energy. Different machine learning methods were explored, including linear regression, support vector regression and decision tree. The best result is obtained by linear regression with predictive features and the performance is improved significantly from the baseline method.
The current status of the Lambda(1405) resonance in the Kbar N scattering is summarized. It is shown that the precise experimental data and the theoretical developments in chiral SU(3) dynamics enable us to quantitatively understand the physics around the Kbar N threshold. We present the recent theoretical predictions of the pi Sigma spectrum and the investigations of the internal structure of the Lambda(1405).
A lepto-baryonic left-right symmetric theory is considered along with pointing out stable dark matter candidates whose stability is ensured automatically where leptons and baryons are defined as local gauge symmetries. These theories are generally anomalous and the possible gauge anomaly free solutions for these theories are presented. It is found that the neutral component of fermion triplets can be a viable dark matter candidate originally introduced for gauge anomaly cancellation. The other dark matter possibilities within this lepto-baryonic left-right symmetric theory are also presented.
Juan Pedro Araque🇵🇹 · Nuno Filipe Castro🇵🇹 · Jose Santiago🇪🇸
Pair production of new vector-like quarks in collisions is considered model independent as it is usually dominated by QCD production. Nonetheless, the presence of a new massive color octet (heavy gluon) in some composite Higgs models may modify the pair production rate of vector-like quarks. This scenario is considered and the possible differences between the usual QCD production and the production mediated via heavy gluons is studied. The sensitivity to these differences in the LHC (run-1 and run-2) are studied. No sizeable differences have been found, which suggests that the published experimental results can be easily reinterpreted by a simple cross-section scaling. This reinterpretation has been also done for the run-1 results published by the collaborations.
The indications in favor of the existence of light sterile neutrinos at the eV scale found in short-baseline neutrino oscillation experiments is reviewed. The future perspectives of short-baseline neutrino oscillation experiments and the connections with beta-decay measurements of the neutrino masses and with neutrinoless double-beta decay experiments are discussed.
In this article, we construct the axialvector-diquark-scalar-diquark-antiquark type and the axialvector-diquark-axialvector-diquark-antiquark type interpolating currents, and study the hidden-charm pentaquark states with the strangeness systematically using the QCD sum rules. The predicted masses of the pentaquark states , and are compatible with the experimental value from the LHCb collaboration, more experimental data are still needed to identify the unambiguously.
Carsten van de Bruck🇬🇧 · Chris Longden🇬🇧
We consider an extension of Higgs inflation in which the Higgs field is coupled to the Gauss-Bonnet term. Working solely in the Jordan frame, we firstly recover the standard predictions of Higgs inflation without a Gauss-Bonnet term. We then calculate the power spectra for scalar and tensor perturbations in the presence of a coupling to a Gauss-Bonnet term. We show that generically the predictions of Higgs inflation are robust and the contributions to the power spectra coming from the Gauss-Bonnet term are negligible. We find, however, that the end of inflation can be strongly modified and that we hence expect the details of (p)reheating to be significantly altered, leading to some concerns over the feasibility of the model which require further investigations.
The High-Luminosity LHC is expected to provide of integrated luminosity. As a result billions of events containing top quarks will be detected at the CMS and ATLAS experiments, allowing for precise measurements of the top quark properties. The experimental challenges that will be faced in a high luminosity environment, with a special focus on top quark related observables are examined. We discuss prospects for measuring top quark anomalous couplings at the HL-LHC. Projections for detecting flavor changing neutral currents involving top quarks are also reviewed.
Keisuke Harigaya🇺🇸 · Yasunori Nomura🇺🇸
We present composite models explaining the diphoton excess of mass around 750 GeV recently reported by the LHC experiments.
Various ideas associated with exotic hadrons, and hadronic structure in general, are briefly reviewed.
Chengcheng Han🇯🇵 · Mihoko M. Nojiri🇯🇵 · Myeonghun Park🇰🇷
Perturbative unitarity conditions have been playing an important role by estimating the energy scale of new physics, including the Higgs mass as one of the most important examples. In this letter, we show that there is a possibility to see the hint of a new physics (top quark partner) indirectly by observing an "apparent" unitarity violation in distribution well above top quark mass in a process of a heavy resonance decaying into a pair of top quarks.
A review of the underlying ideas of the Interacting Quark Diquark Model (IQDM) that asses the baryon spectroscopy in terms of quark diquark degrees of freedom is given, together with a discussion of the missing resonances problem. Some ideas about its generalization the heavy baryon spectroscopy is given.s of freedom is given, together with a discussion of the missing resonances problem. Some ideas about its generalization the heavy baryon spectroscopy is given.The results are compared to the existing experimental data.
Grojean · C (ed.) (CERN) Mulders · M (ed.) (CERN)
The European School of High-Energy Physics is intended to give young physicists an introduction to the theoretical aspects of recent advances in elementary particle physics. These proceedings contain lecture notes on quantum field theory and the Standard Model, quantum chromodynamics, flavour physics, neutrino physics, physics beyond the Standard Model, cosmology, heavy ion physics, statistical data analysis, as well as an account for the physics results with the data accumulated during the first run of the LHC.
Arthur Hebecker🇩🇪 · Jakob Moritz🇩🇪 · Alexander Westphal🇩🇪 · Lukas T. Witkowski🇩🇪
We present a particularly simple model of axion monodromy: Our axion is the lowest-lying KK-mode of the RR-2-form-potential in the standard Klebanov-Strassler throat. One can think of this inflaton candidate as being defined by the integral of over the cycle of the throat. It obtains an exponentially small mass from the IR-region in which the shrinks to zero size both with respect to the Planck scale and the mass scale of local modes of the throat. Crucially, the cycle has to be shared between two throats, such that the second locus where the shrinks is also in a warped region. Well-known problems like the potentially dangerous back-reaction of brane/antibrane pairs and explicit supersymmetry breaking are not present in our scenario. However, the inflaton back-reaction starts to deform the geometry strongly once the field excursion approaches the Planck scale. We derive the system of differential equations required to treat this effect quantitatively. Numerical work is required to decide whether back-reaction makes the model suitable for realistic inflation. While we have to leave this crucial issue to future studies, we find it interesting that such a simple and explicit stringy monodromy model allows an originally sub-Planckian axion to go through many periods with full quantitative control before back-reaction becomes strong. Also, the mere existence of our ultra-light throat mode (with double exponentially suppressed mass) is noteworthy.
Chitrasen Jena (for the ALICE Collaboration)🇮🇹
Hadrons containing heavy quarks, i.e. charm and beauty, are effective probes to investigate the properties of the hot, dense and strongly-interacting medium formed in high-energy nuclear collisions. The relatively large masses of heavy quarks ensure that they are predominantly produced in the early stages of the collision and probe the complete space-time evolution of the expanding medium. The measurements of D-meson production in pp collisions provide an important test of pQCD calculations and serve as an essential baseline for the comprehensive studies in heavy-ion collisions. The study of D-meson production in p-Pb collisions is necessary to disentangle the cold nuclear matter effects from hot nuclear matter effects. The measurement of heavy-flavour production as a function of charged-particle multiplicity in pp and p-Pb collisions could provide insight into the role of multi-parton interactions at LHC energies. We present ALICE results on D-meson production in pp collisions at 7 TeV and p-Pb collisions at 5.02 TeV. The D-meson yields per event, measured in different multiplicity intervals and normalized to their multiplicity-integrated values, are presented for pp and p-Pb collisions. The -differential production cross section and nuclear modification factor of prompt D mesons are measured in p-Pb collisions. The nuclear modification factor, , is compatible with unity within uncertainties, indicating that cold nuclear matter effects are small for GeV/. The D-meson transverse momentum distributions in p-Pb collisions relative to pp collisions, measured in several multiplicity classes, are also discussed.
Grigor Aslanyan🇺🇸 · Layne C. Price🇺🇸 · Jenni Adams🇳🇿 · Torsten Bringmann🇳🇴 · Hamish A. Clark🇦🇺 · Richard Easther🇳🇿 · Geraint F. Lewis🇦🇺 · Pat Scott🇬🇧
Cosmological inflation generates primordial density perturbations on all scales, including those far too small to contribute to the cosmic microwave background. At these scales, isolated ultracompact minihalos of dark matter can form well before standard structure formation, if the perturbations have sufficient amplitude. Minihalos affect pulsar timing data and are potentially bright sources of gamma rays. The resulting constraints significantly extend the observable window of inflation in the presence of cold dark matter, coupling two of the key problems in modern cosmology.
Dmitry Gal'tsov🇷🇺 · Elena Melkumova🇷🇺 · Pavel Spirin🇷🇺
We calculate the radiation accompanying gravitational collision of the domain wall and the point particle in five-dimensional spacetime. This process, which can be regarded as brane-particle bremsstrahlung, here called {\it branestrahlung}, has unusual features. Since the brane has intrinsic dynamics, it gets excited in the course of collision, and, in particular, at the moment of perforation the shock branon wave is generated, which then expands with the velocity of light. Therefore, apart from the time-like source, whose radiation can be computed in a standard way, the total radiation source contains a light-like part whose retarded field is quite non-trivial, exhibiting interesting retardation and memory effects. We analyze this field in detail, showing that, contrary to the claims that the light-like sources should not radiate at all, the radiation is non-zero and has classically divergent spectrum. We estimate the total radiation power introducing appropriate cutoffs. In passing, we explain how the sum of the non-local (with the support inside the light cone) and the local (supported on the cone) singular parts of the Green's function of the five-dimensional d'Alembert equation together define a regular functional.
In this article we study Kaluza-Klein (KK) dimensional reduction of massive Abelian gauge theories with charged matter fields on a circle. Since local gauge transformations change position dependence of the charged fields, the decomposition of the charged matter fields into KK modes is gauge dependent. While whole KK mass spectrum is independent of the gauge choice, the mode number depends on the gauge. The masses of the KK modes also depend on the field value of the zero-mode of the extra dimensional component of the gauge field. In particular, one of the KK modes in the KK tower of each massless 5D charged field becomes massless at particular values of the extra-dimensional component of the gauge field. When the extra-dimensional component of the gauge field is identified with the inflaton, this structure leads to recursive cosmological particle productions.
The invariant mass of tau lepton pairs turns out to be smaller than the resonant mass of their mother particle and the invariant mass distribution is stretched wider than the width of the resonant mass as significant fraction of tau lepton momenta are carried away by neutrinos escaping undetected at collider experiments. This paper describes a new approach to reconstruct resonant masses of heavy particles decaying to tau leptons at such experiments. A typical example is a Z or Higgs boson decaying to a tau pair. Although the new technique can be used for each tau lepton separately, I combine two tau leptons to improve mass resolution by requiring the two tau leptons are lined up in a transverse plane. The method is simple to implement and complementary to the collinear approximation technique that works well when tau leptons are not lined up in a transverse plane. The reconstructed mass can be used as another variable in analyses that already use a visible tau pair mass and missing transverse momentum as these variables are not explicitly used in the stochastic mass-reconstruction to select signal-like events.
Federico Carta🇪🇸 · Fernando Marchesano🇪🇸 · Gianluca Zoccarato🇪🇸
We analyse the structure of Yukawa couplings in local SU(5) F-theory models with enhancement. These models are the minimal setting in which the whole flavour structure for the MSSM charged fermions is encoded in a small region of the entire compactification space. In this setup the symmetry is broken down to SU(5) by means of a 7-brane T-brane background, and further to the MSSM gauge group by means of a hypercharge flux that also implements doublet-triplet splitting. At tree-level only one family of quarks and charged leptons is massive, while the other two obtain hierarchically smaller masses when stringy non-perturbative effects are taken into account. We find that there is a unique model with such hierarchical flavour structure. The relative simplicity of the model allows to perform the computation of Yukawa couplings for a region of its parameter space wider than previous attempts, obtaining realistic fermion masses and mixings for large parameter regions. Our results are also valid for local models with enhancement, pointing towards a universal structure to describe realistic fermion masses within this framework.
Saumen Datta🇮🇳 · Sourendu Gupta🇮🇳 · Andrew Lytle🇬🇧
We explore the use of Wilson flow to study the deconfinement transition in SU(3) gauge theory. We use the flowed Polyakov loop as a renormalized order parameter for the transition, and use it to renormalize the Polyakov loop. We also study the flow properties of the electric and magnetic gluon condensates, and demonstrate that the difference of the flowed operators shows rapid change across the transition point.
* 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.