HEP Phenomenology·hep-ph
39 papers—26 primary·13 cross-listed·reconstructed*
I present a new scheme for tagging boosted heavy flavor jets called " tagging" and its application to TeV-scale physics beyond the Standard Model. Using muons from B hadron decay to define a particular combination "x" of angular information, and jet substructure variables, we identify a clean () good efficiency () tag. I demonstrate the usefulness of this new scheme by showing the reach for discovery of leptophobic and .
Liam Keegan🇨🇭 · Aleksi Kurkela🇨🇭 · Aleksas Mazeliauskas🇺🇸 · Derek Teaney🇺🇸
We use effective kinetic theory, accurate at weak coupling, to simulate the pre-equilibrium evolution of transverse energy and flow perturbations in heavy-ion collisions. We provide a Green function which propagates the initial perturbations to the energy-momentum tensor at a time when hydrodynamics becomes applicable. With this map, the complete pre-thermal evolution from saturated nuclei to hydrodynamics can be modelled in a perturbatively controlled way.
A. Gehrmann-De Ridder🇨🇭 · T. Gehrmann🇨🇭 · E.W.N. Glover🇬🇧 · A. Huss🇨🇭 · T.A. Morgan🇬🇧
The transverse momentum distribution of massive neutral vector bosons can be measured to high accuracy at hadron colliders. The transverse momentum is caused by a partonic recoil, and is determined by QCD dynamics. We compute the single and double-differential transverse momentum distributions for fully inclusive production including leptonic decay to next-to-next-to-leading order (NNLO) in perturbative QCD. We also compute the same distributions normalised to the cross sections for inclusive production, i.e. integrated over the transverse momentum of the lepton pair. We compare our predictions for the fiducial cross sections to the 8 TeV data set from the ATLAS and CMS collaborations, which both observed a tension between data and NLO theory predictions, using the experimental cuts and binning. We find that the inclusion of the NNLO QCD effects does not fully resolve the tension with the data for the unnormalised distribution. However, we observe that normalising the NNLO -boson transverse momentum distribution by the NNLO Drell-Yan cross section substantially improves the agreement between experimental data and theory, and opens the way for precision QCD studies of this observable.
Sanjib Kumar Agarwalla🇮🇳 · Sabya Sachi Chatterjee🇮🇳 · Antonio Palazzo🇮🇹
Present global fits of world neutrino data hint towards non-maximal with two nearly degenerate solutions, one in the lower octant (), and the other in the higher octant (). This octant ambiguity of is one of the fundamental issues in the neutrino sector, and its resolution is a crucial goal of next-generation long-baseline (LBL) experiments. In this letter, we address for the first time, the impact of a light eV-scale sterile neutrino towards such a measurement, taking the Deep Underground Neutrino Experiment (DUNE) as a case study. In the so-called 3+1 scheme involving three active and one sterile neutrino, the transition probability probed in the LBL experiments acquires a new interference term via active-sterile oscillations. We find that this novel interference term can mimic a swap of the octant, even if one uses the information from both neutrino and antineutrino channels. As a consequence, the sensitivity to the octant of can be completely lost and this may have serious implications in our understanding of neutrinos from both the experimental and theoretical perspectives.
Timothy Cohen🇺🇸 · Graham D. Kribs🇺🇸 · Ann E. Nelson🇺🇸 · Bryan Ostdiek🇺🇸
Motivated by the recent excess in the diphoton invariant mass near 750 GeV, we explore a supersymmetric extension of the Standard Model that includes the minimal set of superpartners as well as additional Dirac partner chiral superfields in the adjoint representation for each gauge group. The bino partner pseudoscalar is identified as the 750 GeV resonance, while superpotential interactions between it and the gluino (wino) partners yield production via gluon fusion (decay to photon pairs) at one-loop. The gauginos and these additional adjoint superpartners are married by a Dirac mass and must also have Majorana masses. While a large wino partner Majorana mass is necessary to explain the excess, the gluino can be approximately Dirac-like, providing benefits consistent with being both "supersoft" (loop corrections to the scalar masses from Dirac gauginos are free of logarithmic enhancements) and "supersafe" (the experimental limits on the squark/gluino masses can be relaxed due to the reduced production rate). Consistency with the measured Standard Model-like Higgs boson mass is imposed, and a numerical exploration of the parameter space is provided. Models that can account for the diphoton excess are additionally characterized by having couplings that can remain perturbative up to very high scales, while remaining consistent with experimental constraints, the Higgs boson mass, and an electroweak scale which is not excessively fine tuned.
V. Cirigliano🇺🇸 · W. Dekens🇺🇸 · J. de Vries🇳🇱 · E. Mereghetti🇺🇸
Working in the framework of the Standard Model Effective Field Theory, we study chirality-flipping couplings of the top quark to Higgs and gauge bosons. We discuss in detail the renormalization group evolution to lower energies and investigate direct and indirect contributions to high- and low-energy CP-conserving and CP-violating observables. Our analysis includes constraints from collider observables, precision electroweak tests, flavor physics, and electric dipole moments. We find that indirect probes are competitive or dominant for both CP-even and CP-odd observables, even after accounting for uncertainties associated with hadronic and nuclear matrix elements, illustrating the importance of including operator mixing in constraining the Standard Model Effective Field Theory. We also study scenarios where multiple anomalous top couplings are generated at the high scale, showing that while the bounds on individual couplings relax, strong correlations among couplings survive. Finally, we find that enforcing minimal flavor violation does not significantly affect the bounds on the top couplings.
Clayton Santos Mello (Instituto Tecnológico de Aeronáutica, DCTA, 12.228-900 São José dos Campos, SP, Brazil)🇧🇷 · J. P. B. C. de Melo (Laboratório de Física Teórica e Computacional - LFTC, Universidade Cruzeiro do Sul, 01506-000, São Paulo, SP, Brazil)🇧🇷 · T. Frederico (Instituto Tecnológico de Aeronáutica, DCTA, 12.228-900 São José dos Campos, SP, Brazil)🇧🇷
We study the electromagnetic structure of the pion in terms of the quantum cromodynamic~(QCD) model on the Breit-frame. We calculated the observables, such as the electromagnetic form factor. The priori to have a calculation covariant need to get the valence term of the eletromagnetic form factor. We use the usual formalism in quantum field theory (QFT) and light-front quantum field theory (LFQFT) in order to test the properties of form factor in nonperturbative QCD. In this particular case, the form factor can be obtained using the pion Light-Front (LF) wave function including self-energy from Lattice-QCD. Specifically, these calculations was performed in LF formalism. We consider a quark-antiquark vertex model having a quark self-energy. Also we can use other models to compare the pion electromagnetic form factor with different wave function and to observe the degree of agreement between them.
Stefano Carrazza🇨🇭 · José I. Latorre🇪🇸
One of the most fascinating challenges in the context of parton density function (PDF) is the determination of the best combined PDF uncertainty from individual PDF sets. Since 2014 multiple methodologies have been developed to achieve this goal. In this proceedings we first summarize the strategy adopted by the PDF4LHC15 recommendation and then, we discuss about a new approach to Monte Carlo PDF compression based on clustering through machine learning algorithms.
Teruyuki Kitabayashi🇯🇵 · Masaki Yasuè🇯🇵
In the minimal seesaw model, we derive required constraints on Dirac neutrino masses inducing maximal CP violation in neutrino oscillations. If the maximal atmospheric neutrino mixing is further assumed, Dirac neutrino masses are uniquely determined to respect - flavored CP symmetry for neutrinos.
T.F. Caramés🇪🇸 · A. Valcarce🇪🇸
We present a neat example of a meson--baryon system where the vicinity of two different thresholds enhances the binding of a hadronic resonance, a pentaquark. As a consequence the pattern of states may change when moving among different flavor sectors, what poses a warning on naive extrapolations to heavy flavor sectors based on systematic expansions. For this purpose we simultaneously analyze the and two-hadron systems looking for possible bound states or resonances. When a resonance is controlled by a coupled-channel effect, going to a different flavor sector may enhance or diminish the binding. This effect may, for example, generate significant differences between the charmonium and bottomonium spectra above open-flavor thresholds or pentaquark states in the open-charm and open-bottom sectors.
E. Megias🇩🇪 · E. Ruiz Arriola🇪🇸 · L.L. Salcedo🇪🇸
A heavy quark placed in the medium modifies its specific heat. Using a renormalization group argument we show a low energy theorem in terms of the defect in the trace of the energy-momentum tensor which allows the unambiguous determination of the corresponding entropy shift after imposing the third principle of thermodynamics for degenerate states. We show how recent lattice QCD data can be understood in the confined phase in terms of a single-heavy hadronic spectrum and above the phase transition through power corrections which are analyzed by means of a dimension 2 gluon condensate of the dimensionally reduced theory.
M. Benayoun🇫🇷 · P. David🇫🇷 · L. DelBuono🇫🇷 · F. Jegerlehner🇩🇪
We present an up-to-date analysis of muon evaluations in terms of Mellin-Barnes moments as they might be useful for lattice QCD calculations of . The moments up to 4th order are evaluated directly in terms of --annihilation data and improved within the Hidden Local Symmetry (HLS) Model, supplied with appropriate symmetry breaking mechanisms. The model provides a reliable Effective Lagrangian (BHLS) estimate of the two-body channels plus the channel up to 1.05~GeV, just including the resonance. The HLS piece accounts for 80\% of the contribution to . The missing pieces are evaluated in the standard way directly in terms of the data. We find that the moment expansion converges well in terms of a few moments. The two types of moments which show up in the Mellin-Barnes representation are calculated in terms of hadronic cross--section data in the timelike region and in terms of the hadronic vacuum polarization (HVP) function in the spacelike region which is accessible to lattice QCD (LQCD). In the Euclidean the first type of moments are the usual Taylor coefficients of the HVP and we show that the second type of moments may be obtained as integrals over the appropriately Taylor truncated HVP function. Specific results for the isovector part of are determined by means of HLS model predictions in close relation to --decay spectra.
In light of the observation of a relatively large , one has to consider breaking the - symmetry properly which would otherwise result in a vanishing (as well as ). Therefore, we investigate various symmetry-breaking patterns and accordingly identify those that are phenomenologically viable. Furthermore, the symmetry-breaking effects arising from some specific physics (e.g., the renormalization group equation running effect) are discussed as well.
Subhadeep Mondal🇮🇳 · Santosh Kumar Rai🇮🇳
We consider the production of a heavy neutrino and its possible signals at the Large Hadron-electron Collider (LHeC) in the context of an inverse-seesaw model for neutrino mass generation. The inverse seesaw model extends the Standard Model (SM) particle content by adding two neutral singlet fermions for each lepton generation. It is a well motivated model in the context of generating non-zero neutrino masses and mixings. The proposed future LHeC machine presents us with a particularly interesting possibility to probe such extensions of the SM with new leptons due to the presence of an electron beam in the initial state. We show that the LHeC will be able to probe an inverse scenario with much better efficacy compared to the LHC with very nominal integrated luminosities as well as exploit the advantage of having the electron beam polarized to enhance the heavy neutrino production rates.
Alexandra Dobrynina🇷🇺 · Alexander Kartavtsev🇩🇪 · Georg Raffelt🇩🇪
The helicity of a Dirac neutrino with mass evolves under the influence of a -field because it has a magnetic dipole moment proportional to . Moreover, it was recently shown that a polarized or anisotropic medium engenders the same effect for both Dirac and Majorana neutrinos. Because a -field polarizes a background medium, it instigates helicity oscillations even for Majorana neutrinos unless the medium is symmetric between matter and antimatter. Motivated by these observations, we review the impact of a -field and of an anisotropic or polarized medium on helicity oscillations for Dirac and Majorana neutrinos from the common perspective of in-medium dispersion.
Fabrizio Caola🇨🇭 · Matthew Dowling🇩🇪 · Kirill Melnikov🇩🇪 · Raoul Röntsch🇩🇪 · Lorenzo Tancredi🇩🇪
We compute next-to-leading order (NLO) QCD corrections to the production of two massive electroweak bosons in gluon fusion. We consider both the prompt production process and the production mediated by an exchange of an s-channel Higgs boson, . We include final states with both on- and off-shell vector bosons with leptonic decays. The gluonic production of vector bosons is a loop-induced process, including both massless and massive quarks in the loop. For production, we obtain the NLO QCD corrections to the massive loops through an expansion around the heavy top limit. This approximation is valid below the top production threshold, giving a broad range of invariant masses between the Higgs production and the top production thresholds in which our results are valid. We explore the NLO QCD effects in focusing, in particular, on the interference between prompt and Higgs-mediated processes. We find that the QCD corrections to the interference are large and similar in size to the corrections to both the signal and the background processes. At the same time, we observe that corrections to the interference change rapidly with the four-lepton invariant mass in the region around the ZZ production threshold. We also study the interference effects in production where, due to technical limitations, we only consider contributions of massless loops. We find that the QCD corrections to the interference in this case are somewhat larger than those for either the signal or the background.
Yu-Sheng Liu🇺🇸 · David McKeen🇺🇸 · Gerald A. Miller🇺🇸
A new scalar boson which couples to the muon and proton can simultaneously solve the proton radius puzzle and the muon anomalous magnetic moment discrepancy. Using a variety of measurements, we constrain the mass of this scalar and its couplings to the electron, muon, neutron, and proton. Making no assumptions about the underlying model, these constraints and the requirement that it solve both problems limit the mass of the scalar to between about 100 keV and 100 MeV. We identify two unexplored regions in the coupling constant-mass plane. Potential future experiments and their implications for theories with mass-weighted lepton couplings are discussed.
Shinya Matsuzaki🇯🇵 · Koichi Yamawaki🇯🇵
If the 750 GeV diphoton excess is identified with the color-singlet isosinglet-technipion, (750), in the one-family walking technicolor, as in our previous paper, then there should exist another color-singlet technipion, isotriplet one, , definitely predicted at around 950 GeV independently of the dynamical details. The are produced at the LHC via vector boson and photon fusion processes, predominantly decaying to , and , respectively. Those walking technicolor signals can be explored at the Run 2, or 3, which would further open a way to a plethora of yet other (colored) technipions.
V.P. Pagura🇪🇸 · D. Gómez Dumm🇦🇷 · S. Noguera🇪🇸 · N.N. Scoccola🇦🇷
The magnetic susceptibility of the QCD vacuum is analyzed in the framework of a nonlocal SU(3) Polyakov-Nambu-Jona-Lasinio model. Considering two different model parametrizations, we estimate the values of the and -quark tensor coefficients and magnetic susceptibilities and then we extend the analysis to finite temperature systems. Our numerical results are compared to those obtained in other theoretical approaches and in lattice QCD calculations.
S. Badger🇬🇧 · J. Bendavid🇺🇸 · V. Ciulli🇮🇹 · A. Denner🇩🇪 · R. Frederix🇩🇪 · M. Grazzini🇨🇭 · J. Huston🇺🇸 · M. Schönherr🇨🇭 · K. Tackmann · J. Thaler🇺🇸 · C. Williams (conveners)🇺🇸 · J. R. Andersen🇬🇧 and 83 other authors
This Report summarizes the proceedings of the 2015 Les Houches workshop on Physics at TeV Colliders. Session 1 dealt with (I) new developments relevant for high precision Standard Model calculations, (II) the new PDF4LHC parton distributions, (III) issues in the theoretical description of the production of Standard Model Higgs bosons and how to relate experimental measurements, (IV) a host of phenomenological studies essential for comparing LHC data from Run I with theoretical predictions and projections for future measurements in Run II, and (V) new developments in Monte Carlo event generators.
Heavy quark parton distribution functions (PDFs) play an important role in several Standard Model and New Physics processes. Most PDF analyses rely on the assumption that the charm and bottom PDFs are generated perturbatively by gluon splitting and do not include any non-perturbative degrees of freedom. However, a non-perturbative, intrinsic heavy quark PDFs have been predicted in the literature. We demonstrate that to a very good approximation the scale-evolution of the intrinsic heavy quark content of the nucleon is governed by non-singlet evolution equations, and use this approximation to model the intrinsic bottom distribution and its impact on parton-parton luminosities at the LHC.
Rohini M. Godbole🇮🇳 · Gaurav Mendiratta🇮🇳 · Ambresh Shivaji🇮🇹 · Tim M.P. Tait🇺🇸
A gluphilic scalar dark matter (GSDM) model has recently been proposed as an interesting vision for WIMP dark matter communicating dominantly with the Standard Model via gluons. We discuss the collider signature of a hard jet recoiling against missing momentum ("mono-jet") in such a construction, whose leading contribution is at one-loop. We compare the full one-loop computation with an effective field theory (EFT) treatment, and find (as expected) that EFT does not accurately describe regions of parameter space where mass of the colored mediator particles are comparable to the experimental cuts on the missing energy. We determine bounds (for several choices of SU(3) representation of the mediator) from the 8 TeV data, and show the expected reach of the 13 TeV LHC and a future 100 TeV collider to constrain or discover GSDM models.
Hao Xu🇨🇳 · Xiang Liu🇨🇳 · Takayuki Matsuki🇯🇵
We study the observed decay via rescattering mechanism and show that this branching ratio is well reproduced by this mechanism. We further extend this theoretical framework to investigate the decays of , where the and the are -wave charmonium partners of the . Our results show that the branching ratios, and , are of the order of , which can be accessible at LHCb, Belle and forthcoming BelleII.
Soo-Min Choi🇰🇷 · Yoo-Jin Kang🇰🇷 · Hyun Min Lee🇰🇷
As an interpretation of the 750 GeV diphoton excesses recently reported by both ATLAS and CMS collaborations, we consider a simple extension of the Standard Model with a Dirac fermion dark matter where a singlet complex scalar field mediates between dark matter and SM particles via effective couplings to SM gauge bosons and/or Higgs-portal. In this model, we can accommodate the diphoton events through the direct and/or cascade decays of pseudo-scalar and real scalar partners of the complex scalar field. We show that mono-jet searches and gamma-ray observations are complementary in constraining the region where the width of the diphoton resonance can be enhanced due to the couplings of the resonance to dark matter and the correct relic density is obtained. In the case of cascade decay of the resonance, the effective couplings of singlet scalars can be smaller, but the model is still testable by the future discrimination between single photon and photon-jet at the LHC as well as the gamma-ray searches for the cascade annihilation of dark matter.
L. Maiani🇮🇹 · A.D. Polosa🇮🇹 · V. Riquer🇮🇹
Diquarks are found to have the right degrees of freedom to describe the tetraquark poles in hidden-charm to open-charm meson-meson amplitudes. Compact tetraquarks result as intermediate states in non-planar diagrams of the 1/N expansion and the corresponding resonances are narrower than what estimated before. The proximity of tetraquarks to meson-thresholds has an apparent role in this analysis and, in the language of meson molecules, an halving rule in the counting of states is obtained.
Marcel Krause🇩🇪 · Robin Lorenz🇩🇪 · Margarete Muhlleitner🇩🇪 · Rui Santos🇵🇹 · Hanna Ziesche🇩🇪
The 2-Higgs-Doublet Model (2HDM) belongs to the simplest extensions of the Standard Model (SM) Higgs sector that are in accordance with theoretical and experimental constraints. In order to be able to properly investigate the experimental Higgs data and, in the long term to distinguish between possible models beyond the SM, precise predictions for the Higgs boson observables have to be made available on the theory side. This requires the inclusion of the higher order corrections. In this work, we investigate in detail the renormalization of the 2HDM, a pre-requisite for the computation of higher order corrections. We pay particular attention to the renormalization of the mixing angles and , which diagonalize the Higgs mass matrices and which enter all Higgs observables. The implications of various renormalization schemes in next-to-leading order corrections to the sample processes and are investigated. Based on our findings, we will present a renormalization scheme that is at the same time process independent, gauge independent and numerically stable.
Francesco Knechtli🇩🇪 · Enrico Rinaldi🇺🇸
In this review we summarize the ongoing effort to study extra-dimensional gauge theories with lattice simulations. In these models the Higgs field is identified with extra-dimensional components of the gauge field. The Higgs potential is generated by quantum corrections and is protected from divergencies by the higher dimensional gauge symmetry. Dimensional reduction to four dimensions can occur through compactification or localization. Gauge-Higgs unification models are often studied using perturbation theory. Numerical lattice simulations are used to go beyond these perturbative expectations and to include non-perturbative effects. We describe the known perturbative predictions and their fate in the strongly-coupled regime for various extra-dimensional models.
Norman H. Christ🇺🇸 · Xu Feng🇺🇸 · Antonin Portelli🇬🇧 · Christopher T. Sachrajda🇬🇧
The rare kaon decays are strongly suppressed in the standard model and widely regarded as processes in which new phenomena, not predicted by the standard model, may be observed. Recognizing such new phenomena requires precise standard model prediction for the braching ratio of with controlled uncertainty for both short-distance and long-distance contributions. In this work we demonstrate the feasibility of lattice QCD calculation of the long-distance contribution to rare kaon decays with the emphasis on . Our methodology covers the calculation of both - and -exchange diagrams. We discuss the estimation of the power-law, finite-volume corrections and two methods to consistently combine the long distance contribution determined by the lattice methods outlined here with the short distance parts that can be reliably determined using perturbation theory. It is a subsequent work of our first methodology paper on , where the focus was made on the -exchange diagrams.
We study magnetic field effect on chiral phase transition in a Nambu--Jona-Lasinio model. In comparison with mean field approximation containing quarks only, including mesons as quantum fluctuations in the model leads to a transition from inverse to delayed magnetic catalysis at finite temperature and delays the transition at finite baryon chemical potential. The location of the critical end point depends on the the magnetic field non-monotonously.
Hao Wei🇨🇳 · Xiao-Bo Zou🇨🇳 · Hong-Yu Li🇨🇳 · Dong-Ze Xue🇨🇳
In the present work, we consider the cosmological constant model , which is well motivated from three independent approaches. As is well known, the hint of varying fine structure constant was found in 1998. If is right, it means that the cosmological constant should also be varying. Here, we try to develop a suitable framework to model this varying cosmological constant , in which we view it from an interacting vacuum energy perspective. Then, we consider the observational constraints on these models by using the 293 data from the absorption systems in the spectra of distant quasars. We find that the model parameters can be tightly constrained to the very narrow ranges of typically. On the other hand, we can also view the varying cosmological constant model from another perspective, namely it can be equivalent to a model containing "dark energy" and "warm dark matter", but there is no interaction between them. We find that this is also fully consistent with the observational constraints on warm dark matter.
Keisuke Inomata🇯🇵 · Masahiro Kawasaki🇯🇵 · Yuichiro Tada🇯🇵
We revisit the constraints on the small scale density perturbations () from the modification of the freeze-out value of the neutron-proton ratio at big-bang nucleosynthesis era. Around the freeze-out temperature , the universe can be divided into several local patches which have different temperatures since any perturbation which enters the horizon after the neutrino decoupling has not diffused yet. Taking account of this situation, we calculate the freeze-out value in detail. We find that the small scale perturbations decrease the n-p ratio in contrast to previous works. With use of the latest observed He abundance, we obtain the constraint on the power spectrum of the curvature perturbations as on .
Marco Dias🇧🇷 · Julio M. Hoff da Silva🇧🇷 · Eslley Scatena🇧🇷
We show that the introduction of a minimal length in the context of non-commutative spacetime gives rise (after some considerations) to higher-order theories. We then explicitly demonstrate how these higher-derivative theories appear as a generalization of the standard electromagnetism and general relativity by applying a consistent procedure that modifies the original Maxwell and Einstein-Hilbert actions. In order to set a bound on the minimal length, we compare the deviations from the inverse-square law with the potentials obtained in the higher-order theories and discuss the validity of the results. The introduction of a quantum bound for the minimal length parameter in the higher-order QED allows us to lower the actual limits on the parameters of higher-derivative gravity by almost half of their order of magnitude.
W. S. Hipolito-Ricaldi🇨🇦 · Robert Brandenberger🇨🇦 · Elisa G.M. Ferreira🇨🇦 · L. L. Graef🇨🇦
We consider Parker particle production in the Ekpyrotic scenario (in particular in the New Ekpyrotic model) and show that the density of particles produced by the end of the phase of Ekpyrotic contraction is sufficient to lead to a hot state of matter after the bounce. Hence, no separate reheating mechanism is necessary.
Ujjaini Alam🇮🇳 · Satadru Bag🇮🇳 · Varun Sahni🇮🇳
The phantom brane has several important distinctive features: (i) Its equation of state is phantom-like, but there is no future `big rip' singularity, (ii) the effective cosmological constant on the brane is dynamically screened, because of which the expansion rate is {\em smaller} than that in CDM at high redshifts. In this paper, we constrain the Phantom braneworld using distance measures such as Type Ia supernovae (SNeIa), Baryon Acoustic Oscillations (BAO), and the compressed Cosmic Microwave Background (CMB) data. We find that the simplest braneworld models provide a good fit to the data. For instance, BAO +SNeIa data can be accommodated by the braneworld for a large region in parameter space at . The Hubble parameter can be as high as km/s/Mpc, and the effective equation of state at present can show phantom-like behaviour with at . We note a correlation between and , with higher values of leading to a lower, and more phantom-like, value of . Inclusion of CMB data provides tighter constraints . (Here encodes the ratio of the five and four dimensional Planck mass.) The Hubble parameter in this case is more tightly constrained to km/s/Mpc, and the effective equation of state to . Interestingly, we find that the universe is allowed be closed or open, with , even on including the compressed CMB data. There appears to be some tension in the low and high BAO data which may either be resolved by future data, or act as a pointer to interesting new cosmology.
Claudio Pica🇩🇰 · Thomas A. Ryttov🇩🇰 · Francesco Sannino🇩🇰
We investigate the ultraviolet and infrared fixed point structure of gauge-Yukawa theories featuring a single gauge coupling, Yukawa coupling and scalar self coupling. Our investigations are performed using the two loop gauge beta function, one loop Yukawa beta function and one loop scalar beta function. We provide the general conditions that the beta function coefficients must abide for the theory to be completely asymptotically free while simultaneously possessing an infrared stable fixed point. We also uncover special trajectories in coupling space along which some couplings are both asymptotically safe and infrared conformal.
Amjad Ashoorioon🇮🇹 · Roberto Casadio🇮🇹 · Tomi Koivisto🇸🇪
If the initial quantum state of the primordial perturbations broke rotational invariance, that would be seen as a statistical anisotropy in the angular correlations of the cosmic microwave background radiation (CMBR) temperature fluctuations. This can be described by a general parameterisation of the initial conditions that takes into account the possible direction-dependence of both the amplitude and the phase of particle creation during inflation. The leading effect in the CMBR two-point function is typically a quadrupole modulation, whose coefficient is analytically constrained here to be . The CMBR three-point function then acquires enhanced non-gaussianity, especially for the local configurations. In the large occupation number limit, a distinctive prediction is a modulation of the non-gaussianity around a mean value depending on the angle that short and long wavelength modes make with the preferred direction. The maximal variations with respect to the mean value occur for the configurations which are coplanar with the preferred direction and the amplitude of the non-gaussianity increases (decreases) for the short wavelength modes aligned with (perpendicular to) the preferred direction. For a high scale model of inflation with maximally pumped up isotropic occupation and the difference between these two configurations is about , which could be detectable in the future. For purely anisotropic particle creation, the non-Gaussianity can be larger and its anisotropic feature very sharp. The non-gaussianity can then reach in the preferred direction while disappearing from the correlations in the orthogonal plane.
S. Ferrara🇨🇭 · A. Kehagias🇬🇷 · A. Sagnotti🇮🇹
Abdus Salam was a true master of 20th Century Theoretical Physics. Not only was he a pioneer of the Standard Model (for which he shared the Nobel Prize with S. Glashow and S.Weinberg), but he also (co)authored many other outstanding contributions to the field of Fundamental Interactions and their unification. In particular, he was a major contributor to the development of supersymmetric theories, where he also coined the word "Supersymmetry" (replacing the earlier "Supergauges" drawn from String Theory). He also introduced the basic concept of "Superspace" and the notion of "Goldstone Fermion"(Goldstino). These concepts proved instrumental for the exploration of the ultraviolet properties and for the study of spontaneously broken phases of super Yang-Mills theories and Supergravity. They continue to play a key role in current developments in Early-Universe Cosmology. In this contribution we review models of inflation based on Supergravity with spontaneously broken local supersymmetry, with emphasis on the role of nilpotent superfields to describe a de Sitter phase of our Universe.
A geometrical approach to the calculation of N-point Feynman diagrams is reviewed. It is shown that the geometrical splitting yields useful connections between Feynman integrals with different momenta and masses. It is demonstrated how these results can be used to reduce the number of variables in the occurring functions.
We study the influence of the meson cloud of the nucleon on predictions of the Monte Carlo Glauber model for the charged particle multiplicity density at mid-rapidity in collisions. We find that for central collisions the meson cloud can increase the multiplicity density by \%. The meson-baryon Fock component reduces the required fraction of the binary collisions by a factor of for Au+Au collisions at TeV and for Pb+Pb collisions at TeV.
* 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.