HEP Phenomenology·hep-ph
23 papers—18 primary·5 cross-listed·reconstructed*
Estia J. Eichten🇺🇸 · Chris Quigg🇺🇸
Using a newly developed interquark potential, we tabulate values of the radial Schrödinger wave function or its first nonvanishing derivative at zero quark--antiquark separation, for , , and levels that lie below, or just above, the flavor threshold. These quantities are required inputs for evaluating quarkonium production cross sections.
Michael I. Eides🇺🇸 · Victor Yu. Petrov🇷🇺 · Maxim V. Polyakov🇷🇺
New LHCb Collaboration results on pentaquarks with hidden charm [1] are discussed. These results fit nicely in the hadrocharmonium pentaquark scenario [2,3]. In the new data the old LHCb pentaquark splits into two states and . We interpret these two almost degenerate hadrocharmonium states with and as a result of hyperfine splitting between hadrocharmonium states predicted in [2]. It arises due to QCD multipole interaction between color-singlet hadrocharmonium constituents. We improve the theoretical estimate of hyperfine splitting [2,3] that is compatible with the experimental data. The new state finds a natural explanation as a bound state of and a nucleon, with , and binding energy 42 MeV. As a bound state of a spin-zero meson and a nucleon, hadrocharmonium pentaquark does not experience hyperfine splitting. We find a series of hadrocharmonium states in the vicinity of the wide pentaquark that can explain its apparently large decay width. We compare the hadrocharmonium and molecular pentaquark scenarios and discuss their relative advantages and drawbacks.
Naoyuki Haba🇯🇵 · Yukihiro Mimura🇯🇵 · Toshifumi Yamada🇯🇵
In the minimal SUSY SU(5) GUT with TeV SUSY particles and or below self-coupling for the GUT-breaking Higgs field, the width of the dimension-6 proton decay is suppressed below the reach of Hyper-Kamiokande. In this paper, we point out that a SUSY SO(10) GUT which adopts only GUT-breaking Higgs fields leads to an enhanced dimension-6 proton decay width detectable at Hyper-Kamiokande. The enhancement is because the SU(5)-breaking VEV of arises due to Planck-suppressed terms, , and is therefore substantially larger than the other VEVs that conserve SU(5). As a result, the GUT gauge boson mass is about smaller than the GUT gauge boson mass and can induce a fast dimension-6 proton decay. Through a numerical analysis on threshold corrections of the GUT gauge bosons and the physical components of the GUT-breaking Higgs fields, we confirm that the dimension-6 proton decay can be within the reach of Hyper-Kamiokande.
Xiao-Yun Wang🇨🇳 · Xu-Rong Chen🇨🇳 · Jun He🇨🇳
Inspired by the observation of the pentaquark states and at LHCb, photoproduction of these three states via the interaction is investigated in an effective Lagrangian approach. The -channel Pomeron exchange diffractive process is considered as the main background for the photoproduction. The numerical results show that the theoretical cross section, which is calculated by assuming a branching ratio , is consistent with the existing experimental data of the process. With such a branching ratio, if experimental precision reaches 0.1 nb within a bin of 100 MeV for photon energy, two peaks are expected to be obviously observed in the photoproduction. To observe the two-peak structure from and , higher precision, about 0.1nb/10 MeV, is required to distinguish two close pentaquarks. If the physical branching ratio is larger, the requirement of experimental precision will be reduced. The differential cross sections for reaction are also present. It is found that the -channel Pomeron exchange provides a sharp increase at extreme forward angles and gives a sizable contribution at most energy points, while the contributions from the -channel exchanges play important roles at threshold energies. The experimental measurement of the process in the near-threshold energy region around GeV is suggested, and is accessible at CEBAF@JLab and COMPASS.
The complexity of collider data analyses has dramatically increased from early colliders to the CERN LHC. Reconstruction of the collision products in the particle detectors has reached a point that requires dedicated publications documenting the techniques, and periodic retuning of the algorithms themselves. Analysis methods evolved to account for the increased complexity of the combination of particles required in each collision event (final states) and for the need of squeezing every last bit of sensitivity from the data; physicists often seek to fully reconstruct the final state, a process that is mostly relatively easy at lepton colliders but sometimes exceedingly difficult at hadron colliders to the point of requiring sometimes using advanced statistical techniques such as machine learning. The need for keeping the publications documenting results to a reasonable size implies a greater level of compression or even omission of information with respect to publications from twenty years ago. The need for compression should however not prevent sharing a reasonable amount of information that is essential to understanding a given analysis. Infrastructures like Rivet or HepData have been developed to host additional material, but physicists in the experimental Collaborations often still send an insufficient amount of material to these databases. In this manuscript I advocate for an increase in the information shared by the Collaborations, and try to define a minimum standard for acceptable level of information when reporting the results of statistical procedures in High Energy Physics publications.
Sheng-Tao Li🇨🇳 · Gang Lü🇨🇳
In perturbative QCD approach, we study the direct violation in the decay of via isospin symmetry breaking. An interesting mechanism involving the charge symmetry violating between and is applied to enlarge the violating asymmetry. We find that the violation can be enhanced by the mixing mechanism when the invariant masses of the pairs are in the vicinity of the resonance. For the decay process of , the maximum violation can reach . The possibility of detecting the violation is also presented.
Gavin Bewick🇬🇧 · Silvia Ferrario Ravasio🇬🇧 · Peter Richardson🇨🇭 · Michael H. Seymour🇬🇧
We study the logarithmic accuracy of angular-ordered parton showers by considering the singular limits of multiple emission matrix elements. This allows us to consider different choices for the evolution variable and propose a new choice which has both the correct logarithmic behaviour and improved performance away from the singular regions. In particular the description of event shapes in the non-logarithmic region is significantly improved.
Matthew Lawson🇸🇪 · Alexander J. Millar🇸🇪 · Matteo Pancaldi🇸🇪 · Edoardo Vitagliano🇩🇪 · Frank Wilczek🇸🇪
We propose a new strategy to search for dark matter axions using tunable cryogenic plasmas. Unlike current experiments, which repair the mismatch between axion and photon masses by breaking translational invariance (cavity and dielectric haloscopes), a plasma haloscope enables resonant conversion by matching the axion mass to a plasma frequency. A key advantage is that the plasma frequency is unrelated to the physical size of the device, allowing large conversion volumes. We identify wire metamaterials as a promising candidate plasma, wherein the plasma frequency can be tuned by varying the interwire spacing. For realistic experimental sizes we estimate competitive sensitivity for axion masses eV, at least.
M. Mikhasenko🇩🇪 · Y. Wunderlich🇩🇪 · A. Jackura🇺🇸 · V. Mathieu🇺🇸 · A. Pilloni🇮🇹 · B. Ketzer🇩🇪 · A. P. Szczepaniak🇺🇸
We discuss unitarity constraints on the dynamics of a system of three interacting particles. We show how the short-range interaction that describes three-body resonances can be separated from the long-range exchange processes, in particular the one-pion-exchange process. It is demonstrated that unitarity demands a specific functional form of the amplitude with a clear interpretation: the bare three-particle resonances are dressed by the initial- and final-state interaction, in a way that is consistent with the considered long-range forces. We postulate that the resonance kernel admits a factorization in the energy variables of the initial- and the final-state particles. The factorization assumption leads to an algebraic form for the unitarity equations, which is reminiscent of the well-known two-body-unitarity condition and approaches it in the limit of the narrow-resonance approximation.
Alejandro Ayala🇲🇽 · Luis A. Hernandez🇲🇽 · Marcelo Loewe🇨🇱 · J. C. Rojas🇨🇱 · Renato Zamora🇨🇱
We use the linear sigma model coupled to quarks to explore the location of the phase transition lines in the QCD phase diagram from the point of view of chiral symmetry restoration at high temperature and baryon chemical potential. We compute analytically the effective potential in the high- and low-temperature approximations up to sixth order, including the contribution of the ring diagrams to account for the plasma screening properties. We determine the model parameters, namely, the couplings and mass-parameter, from conditions valid at the first order phase transition at vanishing temperature and, using the Hagedorn limiting temperature concept applied to finite baryon density, for a critical baryochemical potential of order of the nucleon mass. We show that when using the set of parameters thus determined, the second order phase transition line (our proxy for the crossover transition) that starts at finite temperature and zero baryon chemical potential converges to the line of first order phase transitions that starts at zero temperature and finite baryon chemical potential to determine the critical end point to lie in the region , , where is the critical transition temperature at zero baryon chemical potential.
Nodoka Yamanaka🇫🇷 · Jean-Philippe Lansberg🇫🇷 · Hua-Sheng Shao🇫🇷 · Yu-Jie Zhang🇨🇳
Quarkonium production in proton-proton collision is interesting in profiling the partons inside the nucleon. Recently, the impact of double parton scatterings (DPSs) was suggested by experimental data of associated quarkonium production (J/psi+Z, J/psi+W, and J/psi+J/psi) at the LHC and Tevatron, in addition to single parton scatterings (SPSs). In this proceedings contribution, we review the extraction of the effective parameter of the DPS through the evaluation of the SPS contributions under quark-hadron duality.
David d'Enterria🇨🇭 · Daniel E. Martins🇧🇷 · Patricia Rebello Teles🇧🇷
The production of the Higgs boson in photon-photon interactions with proton and nucleus beams at three planned or proposed future CERN colliders --- the high-luminosity Large Hadron Collider (HL-LHC), the high-energy LHC (HE-LHC), and the Future Circular Collider (FCC) --- is studied. The cross sections for the process AA(A)H(A), with the ions A surviving the interaction and the Higgs scalar exclusively produced, are computed with MadGraph 5 modified to include the corresponding elastic fluxes, for Pb-Pb, Xe-Xe, Kr-Kr, Ar-Ar, O-O, p-Pb, and p-p over the nucleon-nucleon collision energy range --100 TeV. Simulations of the decay mode --- including realistic (mis)tagging and reconstruction efficiencies for the final-state b-jets, as well as appropriate kinematical selection criteria to reduce the similarly computed continuum backgrounds --- have been carried out. Taking into account the expected luminosities for all systems, the yields and significances for observing the Higgs boson in ultraperipheral collisions (UPCs) are estimated. At the HL-LHC and HE-LHC, the colliding systems with larger Higgs significance are Ar-Ar(6.3 TeV) and Kr-Kr(12.5 TeV) respectively, but evidence for two-photon Higgs production would require 200 and 30 times larger integrated luminosities than those planned today at both machines. Factors of ten can be gained by running for a year, rather than the typical 1-month heavy-ion LHC operation, but the process will likely remain unobserved until a higher energy hadron collider, such as the FCC, is built. In the latter machine, the observation of Higgs production in UPCs is feasible in just the first nominal run of Pb-Pb and p-Pb collisions at and 63 TeV respectively.
We revisit the constraints on the properties of right handed neutrinos from the requirement to explain the observed light neutrino oscillation data in the type-I seesaw model. We use well-known relations to show that there is in general no lower bound on the mixing of a given heavy neutrino with any individual Standard Model generation. Lower bounds quoted in the literature only apply if the masses of the heavy neutrinos are so degenerate that they cannot be distinguished experimentally. A lower bound on the total mixing (summed over Standard Model generations) can be derived for each heavy neutrino individually, but it strongly depends on the mass of the lightest Standard Model neutrino and on the number of heavy neutrinos that contribute to the seesaw mechanism. Our results have implications for the perspectives of future colliders or fixed target experiments to rule out certain mass ranges for heavy neutrinos.
Despite the lack of evidence of new physics at colliders, neutrino masses, dark matter and matter-antimatter asymmetry of the universe require an extension of the Standard Model. After discussing some new concepts and tools in the description of seesaw neutrino models, such as motion in flavour lepton space and the introduction of the bridging matrix that nicely complements the orthogonal matrix, I discuss recent developments in the connections between neutrino data and scenarios of leptogenesis within some well motivated extensions of the Standard Model. Finally, I briefly review a simple unified picture of neutrino masses, leptogenesis and dark matter based on an extension of the seesaw Lagrangian where a non-renormalizable effective operator coupling right-handed neutrinos to the Higgs is introduced. This operator enhances the right-handed neutrino mixing between a coupled heavy right-handed neutrino and a decoupled one playing the role of dark matter. Interference between the two coupled RH neutrinos generate usual violation so that one can also achieve successful leptogenesis. Although the dark matter right-handed neutrino escapes direct and collider searches, its decays produce a detectable contribution to the very high energy neutrino flux now discovered by IceCube, so that the model is predictive and can be tested at neutrino telescopes.
Zhoudunming Tu🇺🇸 · Dmitri Kharzeev🇺🇸 · Thomas Ullrich🇺🇸
In 1935, in a paper entitled "Can quantum-mechanical description of reality be considered complete?", Einstein, Podolsky, and Rosen (EPR) formulated an apparent paradox of quantum theory. They considered two quantum systems that were initially allowed to interact, and were then later separated. A measurement of a physical observable performed on one system then had to have an immediate effect on the conjugate observable in the other system - even if the systems were causally disconnected! The authors viewed this as a clear indication of the inconsistency of quantum mechanics. In the parton model of the nucleon formulated by Bjorken, Feynman, and Gribov, the partons (quarks and gluons) are viewed by an external hard probe as independent. The standard argument is that, inside the nucleon boosted to an infinite-momentum frame, the parton probed by a virtual photon with virtuality Q is causally disconnected from the rest of the nucleon during the hard interaction. Yet, the parton and the rest of the nucleon have to form a colour-singlet state due to colour confinement, and so have to be in strongly correlated quantum states - we thus encounter the EPR paradox at the sub-nucleonic scale. In this paper, we propose a resolution of this paradox based on the quantum entanglement of partons. We devise an experimental test of entanglement, and carry it out using data on proton-proton collisions from the Large Hadron Collider (LHC). Our results provide a strong direct indication of quantum entanglement at sub-nucleonic scales.
Zackaria Chacko🇺🇸 · Can Kilic🇺🇸 · Saereh Najjari🇧🇪 · Christopher B. Verhaaren🇺🇸
We consider the collider signals arising from kinetic mixing between the hypercharge gauge boson of the Standard Model and its twin counterpart in the Mirror Twin Higgs model, in the framework in which the twin photon is massive. Through the mixing, the Standard Model fermions acquire charges under the mirror photon and the mirror Z boson. We determine the current experimental bounds on this scenario, and show that the mixing can be large enough to discover both the twin photon and the twin Z at the LHC, or at a future 100 TeV hadron collider, with dilepton resonances being a particularly conspicuous signal. We show that, in simple models, measuring the masses of both the mirror photon and mirror Z, along with the corresponding event rates in the dilepton channel, overdetermines the system, and can be used to test these theories.
Javier F. Acevedo🇨🇦 · Joseph Bramante🇨🇦
It was recently demonstrated that asymmetric dark matter can ignite supernovae by collecting and collapsing inside lone sub-Chandrasekhar mass white dwarfs, and that this may be the cause of Type Ia supernovae. A ball of asymmetric dark matter accumulated inside a white dwarf and collapsing under its own weight, sheds enough gravitational potential energy through scattering with nuclei, to spark the fusion reactions that precede a Type Ia supernova explosion. In this article we elaborate on this mechanism and use it to place new bounds on interactions between nucleons and asymmetric dark matter for masses GeV. Interestingly, we find that for dark matter more massive than GeV, Type Ia supernova ignition can proceed through the Hawking evaporation of a small black hole formed by the collapsed dark matter. We also identify how a cold white dwarf's Coulomb crystal structure substantially suppresses dark matter-nuclear scattering at low momentum transfers, which is crucial for calculating the time it takes dark matter to form a black hole. Higgs and vector portal dark matter models that ignite Type Ia supernovae are explored.
Joshua Davies🇩🇪 · Florian Herren🇩🇪 · Go Mishima🇩🇪 · Matthias Steinhauser🇩🇪
We compute the real-radiation corrections to Higgs boson pair production at next-to-next-to-leading order in QCD, in an expansion for large top quark mass. We concentrate on the radiative corrections to the interference contribution from the next-to-leading order one-particle reducible and the leading order amplitudes. This is a well defined and gauge invariant subset of the full real-virtual corrections to the inclusive cross section. We obtain analytic results for all phase-space master integrals both as an expansion around the threshold and in an exact manner in terms of Goncharov polylogarithms.
Erich Poppitz🇨🇦 · Thomas A. Ryttov🇩🇰
We discuss an exotic phase that adjoint QCD possibly exhibits in the deep infrared (IR). It is a confining phase, with a light spectrum consisting of massless composite fermions. The discrete chiral symmetry is broken, with unbroken continuous chiral symmetry. We argue that it may give a description of the IR of adjoint QCD with three massless Weyl flavors and that it passes all consistency checks known to us.
H.C. Chandola🇮🇳 · Deependra Singh Rawat🇮🇳 · H.C. Pandey🇮🇳 · Dinesh Yadav🇮🇳 · H. Dehnen🇩🇪
In order to study the detailed dynamics and associated non-perturbative features of QCD, a dual version of the color gauge theory based on the topologically viable homogeneous fiber bundle approach has been analysed taking into account its magnetic symmetry structure. In the dynamically broken phase of magnetic symmetry, the associated flux tube structure on a S 2 -sphere in the magnetically condensed state of the dual QCD vacuum has been analyzed for the profiles of the color electric field using flux quantization and stability conditions. The color electric field has its intimate association with the vector mode of the magnetically condensed QCD vacuum and such field configurations have been analyzed to show that the color electric flux gets localized towards the poles for a large sphere case while it gets uniformly distributed for the small sphere case in the infrared sector of QCD. The critical flux tube densities have been computed for various couplings and are shown to be in agreement with that for lead-ion central collisions in the near infrared sector of QCD. The possible annihilation/unification of flux tubes under some typical flux tube density and temperature conditions in the magnetic symmetry broken phase of QCD has also been analyzed and shown to play an important role in the process of QGP formation. The thermal variation of the profiles of the color electic field is further investigated which indicates the survival of flux tubes even in the thermal domain that leads the possibility of the formation of some exotic states like QGP in the intermedate regime during the quark-hadron phase transition.
Jeppe Dakin🇩🇰 · Steen Hannestad🇩🇰 · Thomas Tram🇩🇰
We present -body simulations in which either all, or a fraction of, the cold dark matter decays non-relativistically to a relativistic, non-interacting dark radiation component. All effects from radiation and general relativity are self-consistently included at the level of linear perturbation theory, and our simulation results therefore match those from linear Einstein-Boltzmann codes such as CLASS in the appropriate large-scale limit. We also find that standard, Newtonian -body simulations adequately describe the non-linear evolution at smaller scales () in this type of model, provided that the mass of the decaying component is modified correctly, and that the background evolution is correctly treated. That is, for studies of small scales, effects from general relativity and radiation can be safely neglected.
Daniel G. Figueroa🇨🇭 · Adrien Florio🇨🇭 · Mikhail Shaposhnikov🇨🇭
We study fermion number non-conservation (or chirality breaking) in Abelian gauge theories at finite temperature. We consider the presence of a chemical potential for the fermionic charge, and monitor its evolution with real-time classical lattice simulations. This method accounts for short-scale fluctuations not included in the usual effective magneto-hydrodynamics (MHD) treatment. We observe a self-similar decay of the chemical potential, accompanied by an inverse cascade process in the gauge field that leads to a production of long-range helical magnetic fields. We also study the chiral charge dynamics in the presence of an external magnetic field , and extract its decay rate . We provide in this way a new determination of the gauge coupling and magnetic field dependence of the chiral rate, which exhibits a best fit scaling as . We confirm numerically the fluctuation-dissipation relation between and , the Chern-Simons diffusion rate, which was obtained in a previous study. Remarkably, even though we are outside the MHD range of validity, the dynamics observed are in qualitative agreement with MHD predictions. The magnitude of the chiral/diffusion rate is however a factor times larger than expected in MHD, signaling that we are in reality exploring a different regime accounting for short scale fluctuations. This discrepancy calls for a revision of the implications of fermion number and chirality non-conservation in finite temperature Abelian gauge theories, though not definite conclusion can be made at this point until hard-thermal-loops (HTL) are included in the lattice simulations.
The quark matter created in relativistic nuclear collisions is interpreted as a nearly-perfect fluid. The recent efforts to explore its finite-density properties in the beam energy scan programs motivate one to revisit the issue of the local rest frame fixing in off-equilibrium hydrodynamics. I first investigate full second-order relativistic hydrodynamics in the Landau and the Eckart frames. Then numerical hydrodynamic simulations are performed to elucidate the effect of frame choice on flow observables in relativistic nuclear collisions. The results indicate that the flow can differ in the Landau and the Eckart frames but charged particle and net baryon rapidity distributions are mostly frame independent when off-equilibrium kinetic freeze-out is considered.
* 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.