New physics at 1 TeV?

If decays of a heavy particle S are responsible for the diphoton excess with invariant mass 750 GeV observed at the 13 TeV LHC run, it can be easily accommodated in the Standard Model. Two scenarios are considered: production in gluon fusion through a loop of heavy isosinglet quark(s) and production in photon fusion through a loop of heavy isosinglet leptons. In the second case, many heavy leptons are needed or/and they should have large electric charges in order to reproduce experimental data on σ_{pp → SX} · Br(S → γγ).     

Measurement of 10–100 TeV cosmic ray anisotropy at upgraded Carpet-2 installation

The first results obtained during one year of measurements at the upgraded shower Carpet-2 installation at the Baksan Neutrino Observatory of the Institute for Nuclear Research, Russian Academy of Sciences, are presented. The results of calculation of the energy response of the installation are given. The results of data analysis using the standard method and the East-West method are compared. The constraints on amplitudes of harmonics of solar anisotropy for three values of primary energy: E > 12 TeV, E > 40 TeV, and E > 70 TeV, are obtained.     

Constituent quark number scaling from strange hadron spectra in pp collisions at ■=13 TeV

We show that the p_T spectra of Ω~- and φ at midrapidity in the inelastic events in pp collisions at ■=13 TeV exhibit a constituent quark number scaling property,which is a clear signal of quark combination mechanism at hadronization.We use a quark combination model with equal velocity combination approximation to systematically study the production of identified hadrons in pp collisions at ■=13 TeV.The midrapidity spectra for protons,∧,Ξ~-,Ω~-,φ and K~* in the inelastic events are simultaneously fitted by the model.The multiplicity dependence of the yields of these hadrons are also well understood.The strong p_T dependence of the p/φ ratio is well explained by the model,which further suggests that the production of two hadrons with similar masses is determined by their quark content at hadronization.The p_T spectra of strange hadrons at midrapidity in different multiplicity classes in pp collisions at ■=13 TeV are predicted for further tests of the model.The midrapidity p_T spectra of soft (p_T 2 GeV/c)strange quarks and up/down quarks at hadronization in pp collisions at ■=13 TeV are extracted.     

Ψ and Υ Production in p-p Collisions at E = 5, 14 TeV; and Comparison with Experiment at E = 7 TeV

This brief report is an extension of our recent studies of Ψ and Υ production cross sections in proton-proton collisions with E \(=\sqrt {s}=13\) TeV to E = 5 and E =14 TeV, using the mixed heavy quark hybrid theory in which the Ψ(2S) and Υ(3S) are 50 % hybrid states. Also, comparison with recent experiments at E = 7 TeV are used to test the mixed heavy hybrid theory.     

Cross sections of the interactions of4He nuclei with protons at 8·6 and 13·6 GeV/c

⁴He-p collisions at two values of⁴He momenta-8·6 GeV/c and 13·6 GeV/c — have been studied using the one-metre JINR hydrogen bubble chamber. Total, elastic and topological cross sections have been measured. The results are in agreement with other published data. The elastic differential cross section was compared with the predictions of the Glauber model formalism.Dedicated to Academician Václav Votruba on ths occasion of his eightieth birthday.We would like to thank Mrs. M. Stehlíková for drawing the figures.     

Study of Pseudorapidity and Transverse-Momentum Distributions of Charged Particles in pp Interactions at √s = 13 TeV Using Hadron Production Models

Pseudorapidity (η) and Transverse momentum (p_T) distributions of charged particles produced in proton-proton (pp) collisions at √s = 13 TeV are studied. Transverse momentum distributions of charged particles are considered in the Pseudorapidity region of |η| < 0.8 and in the transverse momentum range of 0 < p_T < 20 GeV/c. EPOS1.99, EPOS-LHC and QGSJETII-04 models are used to perform simulations. In order to check the validity of simulations performed using these Monte-Carlo event generators, the results are compared to the measurements of ALICE experiment at the LHC CERN. For the p_T distribution, the EPOS1.99 and QGSJET underpredict the experimental data while the EPOS-LHC model reproduced the distribution very well. EPOS-LHC model describes the experimental data very well as compared to the other two models for the ratio of p_T spectra of charged particles at √s = 13 TeV to 7 TeV. EPOS-LHC also describes the pseudorapidity distribution very well while the EPOS 1.99 and QGSJETII-04 underpredict and overpredict the distribution respectively.

     

NNLO QCD predictions of electron charge asymmetry for inclusive pp→W+X production in forward region at 13 and 14 TeV

This paper presents perturbative QCD predictions of the electron charge asymmetry for inclusive W~±X→e~±v+X production in proton-proton(pp) collisions.Perturbative QCD calculations are performed at nextto-next-to-leading order(NNLO) accuracy using different parton distribution function(PDF) models at 8,13,and 14 TeV center-of-mass energies of CERN LHC pp collisions.NNLO calculations are performed for electrons with transverse momenta above 20 GeV in the forward electron pseudorapidity region 2.0 ≤η_e≤4.25.NNLO predictions are first compared at 8 TeV with the measurements of the LHCb experiment at the LHC for the W~+/W~-cross section ratio and charge asymmetry distributions.The 8 TeV predictions using NNPDF3.1,CT14,and MMHT2014 PDF sets are reported to be in good agreement with the LHCb data for the entire η_e region,justifying the extension of the calculations to 13 and 14 TeV energies.The charge asymmetry predictions at NNLO accuracy are reported in the forward η_e bins at 13 and 14 TeV and compared among NNPDF3.1,CT14,and MMHT2014 PDF sets.Overall,the predicted W~± differential cross-section and charge asymmetry distributions based on different PDF sets are found to be consistent with each other for the entire η_e region.The charge asymmetry distributions are shown to be more sensitive to discriminate among different PDF models in terms of the 14 TeV predictions.     

Discovery potential of Higgs boson pair production through 4■+■ final states at a 100 TeV collider

We explore the discovery potential of Higgs pair production at a 100 Te V collider via full leptonic mode.The same mode can be explored at the LHC when Higgs pair production is enhanced by new physics. We examine two types of fully leptonic final states and propose a partial reconstruction method, which can reconstruct some useful kinematic observables. It is found that the m T2 variable determined by this reconstruction method and the reconstructed visible Higgs mass are crucial to discriminate the signal and background events. It is also noticed that a new variable, denoted as ?m, which is defined as the mass difference of two possible combinations, is very useful as a discriminant. To examine the detector effects, we consider seven detector setups for a 100 Te V collider and investigate the changes in the sensitivity, and we find that lepton isolation and the minimal lepton P t cut are crucial in order to reduce the integrated luminosity.     

Density functional study of the decomposition pathways of SiH? and GeH? at the Si(100) and Ge(100) surfaces

By means of first-principles calculations we studied the decomposition pathways of SiH? on Ge(100) and of GeH? on Si(100), of interest for the growth of crystalline SiGe alloys and Si/Ge heterostructures by plasma-enhanced chemical vapor deposition. We also investigated H desorption via reaction of two adsorbed SiH?/GeH? species (β? reaction) or via Eley-Rideal abstraction of surface H atoms from the impinging SiH? and GeH? species. The calculated activation energies for the different processes suggest that the rate-limiting step for the growth of Si/Ge systems is still the β? reaction of two SiH? as in the growth of crystalline Si.     

Multiplicity fluctuations of pions and protons at SPS energy — An in-depth analysis with factorial correlator

We compute the factorial correlators to study the dynamical fluctuations of pions and a combination of pions and protons (compound multiplicity) in ³²S-AgBr interactions at 200 A GeV. The study reveals that for both pion and compound multiplicity the correlated moments increase with the decrease in bin-bin separation D, following a power-law, which suggests the self-similarity of multiplicity fluctuation in each case. The results of the analysis also show a consistency with the prediction of α-model for the existence of intermittency in both cases.     

Search for Resonant WW and WZ Production in pp collisions at √s=1.96 TeV

We search for resonant WW or WZ production by using up to 5.4 fb(-1) of integrated luminosity collected by the D0 experiment in run II of the Fermilab Tevatron Collider. The data are consistent with the standard model background expectation, and we set limits on a resonance mass by using the sequential standard model W' boson and the Randall-Sundrum model graviton G as benchmarks. We exclude a sequential standard model W' boson in the mass range 180-690 GeV and a Randall-Sundrum graviton in the range 300-754 GeV at 95% C.L.     

Measurement of the cross-section of Zγ and limits on ADD models at the CMS with 7?TeV Large Hadron Collider data

The measurement of the inclusive cross-section for Z?? production at LHC with 7?TeV proton?Cproton collision is presented. The electron and muon decay modes are used to reconstruct the Z boson. The total cross-section is measured for photon transverse energy greater than 10?GeV and with photon and charged lepton separation in the pseudorapidity-azimuthal angle plane greater than 0.7. This study is extended by a measurement of $Z(\nu\bar{\nu})\gamma $ cross-section. A search is performed for extra dimensions in the Arkani-Hamed, Dimopoulos, Dvali framework using the final state of a graviton and photon. The limits are extended with MD?>?1.25?C1.31?TeV for n?=?2?C6. The measurement is found to be in agreement with the Standard Model prediction.     

Prospects for constrained supersymmetry at $$\sqrt{s}={33}\,\text {TeV} $$ and $$\sqrt{s}={100}\,\text {TeV} $$ proton–proton super-colliders

Successful models of pure gravity mediation (PGM) with radiative electroweak symmetry breaking can be expressed with as few as two free parameters, which can be taken as the gravitino mass and \(\tan \beta \) . These models easily support a 125–126 GeV Higgs mass at the expense of a scalar spectrum in the multi-TeV range and a much lighter wino as the lightest supersymmetric particle. In these models, it is also quite generic that the Higgs mixing mass parameter, \(\mu \) , which is determined by the minimization of the Higgs potential is also in the multi-TeV range. For \(\mu >0\) , the thermal relic density of winos is too small to account for the dark matter. The same is true for \(\mu <0\) unless the gravitino mass is of order 500 TeV. Here, we consider the origin of a multi-TeV \(\mu \) parameter arising from the breakdown of a Peccei–Quinn (PQ) symmetry. A coupling of the PQ-symmetry breaking field, \(P\) , to the MSSM Higgs doublets, naturally leads to a value of \(\mu \sim \langle P \rangle ^2 /M_P \sim {\mathcal O}(100)\) TeV and of the order that is required in PGM models. In this case, axions make up the dark matter or some fraction of the dark matter with the remainder made up from thermal or non-thermal winos. We also provide solutions to the problem of isocurvature fluctuations with axion dark matter in this context.     

Carpet—2 Search for Gamma Rays above 100 TeV in Coincidence with HAWC and IceCube Alerts

JETP Letters - We report on the search of astrophysical gamma rays with energies in the 100 TeV to several PeV range arriving in directional and temporal coincidence with public alerts from HAWC...