The Decrease of the ESEEM Frequency of $${\text{P}}_{700}^{ + } {\text{A}}_{1}^{ - }$$ Ion-Radical Pair in Photosystem I Embedded in Trehalose Glassy Matrix at Room Temperature can be Explained by Acceleration of Spin–Lattice Relaxation

The main observation in this work is a decrease in the modulation frequency of the primary electron spin-echo decay (ESEEM) of the \({\text{P}}_{ 7 0 0}^{ + }\) cofactor in the reaction center of Photosystem I (PS I) from cyanobacteria Synechocystis sp. PCC 6803 embedded in dry trehalose matrix as the temperature rises from 150 K to room temperature. From the previous studies of the EPR spectrum shape of this system, it is known that, in dry trehalose matrix at room temperature, the distance between \({\text{P}}_{ 7 0 0}^{ + }\) and \({\text{A}}_{ 1}^{ - }\) spins does not increase compared to the distance measured in glycerol–water solution at cryogenic temperature. From the present ESEEM study, we conclude that the decrease of modulation frequency with rising temperature in trehalose matrix can be fully attributed to the influence of accelerated spin–lattice relaxation of \({\text{A}}_{ 1}^{ - }\). Our calculations show that this requires a decrease in the spin–lattice relaxation time from 3 to 1 μs. To the best of our knowledge, this is the first time that a shift in the ESEEM frequency due to the dipole–dipole interaction between the spins is observed that is caused by spin–lattice relaxation. Based on the above-mentioned results, we formulate a model of the protective effect of trehalose matrix on the electron transfer in the reaction center of PS I that is based on different hydrogen-bond networks between trehalose, local water, and protein.     

Kinetic freeze-out s pectra of identified particles produced in p–Pb collisions at $$\sqrt {s_{NN} }$$ = 5.02 TeV

We study the transverse momentum spectra of identified pions (π^– + π⁺), kaons ((K ^– + K ⁺), K ₀ ^s ), protons (p + p?) and lambda hyperons (Λ + Λ?) produced at mid-rapidity (0 < y _cm < 0.5) in most central (0?5)% p–Pb collisions at \(\sqrt {s_{NN} }\) = 5.02 TeV in comparison with a Unified Statistical Thermal Freeze-out Model (USTFM). The measurements for pions are reported upto p _T = 3 GeV, the kaons (K ^– + K ⁺) are reported upto p _T = 2.5 GeV, K ₀ ^s is reported upto p _T = 7 GeV, and the baryons (protons and lambda hyperons) are reported upto p _T = 3.5 GeV. A good agreement is seen between the calculated results and the experimental data points taken from the ALICE experiment. The transverse momentum spectra are found to be flatter for heavy particles than for light particles. Bulk freeze-out properties in terms of kinetic freeze-out temperature and the transverse collective flow velocity are extracted from the fits of the transverse momentum spectra of these hadrons. The effect of resonance decay contributions has also been taken care of.     

Circular Polarization of γ-Quantum in Radiative Decay H ⇒ f ¯ fγ $$ Hboldsymbol{Rightarrow}overline{f} fgamma $$ (II)

Russian Physics Journal - Within the framework of the Standard Model, the channel of the Higgs boson radiative decay into a fermion-antifermion pair $$...     

Study of fermion pair production in \mathrm{e^+ e^-} collisions at 130–183 GeV

The cross sections and forward-backward asymmetries of hadronic and leptonic events produced in collisions at centre-of-mass energies from 130 to 183 GeV are presented. Results for , , , , and production show no significant deviation from the Standard Model predictions. This enables constraints to be set upon physics beyond the Standard Model such as four-fermion contact interactions, leptoquarks, bosons and R-parity violating squarks and sneutrinos. Limits on the energy scale of contact interactions are typically in the range from 2 to 10 TeV. Limits on R-parity violating sneutrinos reach masses of a few hundred GeV/ for large values of their Yukawa couplings. Received: 8 March 1999 / Published online: 8 December 1999     

Review of single vector boson production in pp collisions at \sqrt{s} = 7 TeV

This review summarises the main results on the production of single vector bosons in the Standard Model, both inclusively and in association with light- and heavy-flavour jets, at the Large Hadron Collider in proton–proton collisions at a centre-of-mass energy of \(7\,{\mathrm {\ TeV}}\) . The general purpose detectors at this collider, ATLAS and CMS, each recorded an integrated luminosity of \({\approx } 40\,\mathrm{pb^{-1}}\) and \(5\,\mathrm{fb^{-1}}\) in the years 2010 and 2011, respectively. The corresponding data offer the unique possibility to precisely study the properties of the production of heavy vector bosons in a new energy regime. The accurate understanding of the Standard Model is not only crucial for searches of unknown particles and phenomena but also to test predictions of perturbative Quantum-Chromodynamics calculations and for precision measurements of observables in the electroweak sector. Results from a variety of measurements in which single \(W\)  or \(Z\)  bosons are identified are reviewed. Special emphasis in this review is given to interpretations of the experimental results in the context of state-of-the-art predictions.     

One-loop gg\to b\bar{b} effects in the main irreducible background to exclusive H\to b\bar{b} production at the LHC

We calculate the amplitude of $gg\to b\bar{b}$ production for the colour singlet, J _z =0, di-gluon state at $\mathcal{O}(\alpha_{\mathrm{S}}^{2})$ order. We consider the cancellation and a realistic cut-off, of the infrared divergent terms. We show that the one-loop radiative QCD contributions effectively reduce the Born level result for the central exclusive $b\bar{b}$ cross section at the LHC. This process is essentially the only irreducible QCD background to the exclusive $H\to b\bar{b}$ signal.     

Analysis of Transverse-Momentum Distributions of Charged Particles in Proton–Proton Collisions at Energies in the Range of $$\boldsymbol{(s_{nn})^{1/2}=2.76}$$ –7 TeV at the LHC

Physics of Atomic Nuclei - Experimental transverse-momentum distributions measured by the ALICE Collaboration for charged pions and kaons, protons, and antiprotons at midrapidities in inelastic...     

Phenomenology of spin observables in the reactions of meson production with the 1 S 0 Diproton pN → {pp} s X

Formalism for spin observables for production of pseudoscalar, scalar, and vectormesons in pN collision with formation of the ¹ S ₀ diproton {pp} _s in the final state is considered in model-independent way assuming parity and angular momentum conservation. Production of the pseudoscalar mesons (J ^π = 0^?) is described by two spin amplitudes and both of them can be completely determined by measurement of unpolarized cross section dσ ₀, vector analyzing power A _y , and spin-correlation coefficients C _x,x = ?C _z,z > and C _x,z . Similar result is obtained for production of scalar mesons (J ^π = 0⁺). It is shown that measurement of the tensor polarization t ₂₀ of the vector meson V (J ^π = 1^?) in the reaction pN → {pp} _s V in collinear kinematics gives the same information as measurement of the spin-correlation coefficients C _z,z or C _y,y .     

Study of direct photon plus jet production in CMS experiment at $\sqrt{s}$ = 14 TeV

We present simulation results of γ+jet analysis using CMS (compact muon solenoid) object-oriented software at the large hadron collider (LHC) center of mass energy = 14 TeV. The study of direct photon production helps in validating the perturbative quantum chromodynamics (pQCD) and providing information on the gluon distribution in the nucleons. Direct photon processes also constitute a major background to several other standard model (SM) processes and signals of new physics. Thus these processes need to be understood precisely in the new energy regime. In this work, we have done a detailed study of the GEANT4 simulated γ+jet events generated with Pythia, and the related background processes. Isolation cuts have been optimized for direct photon which improves the signal over background ratio by ∼25% as compared to previous studies done in CMS. The inclusion of a large Δφ cut between the photon and the leading jet at 40° in the analysis leads to a further increase of ∼15% in S/B, thus giving an overall gain of ∼42% in S/B ratio.     

Centrality, Rapidity, and Transverse-Momentum Dependence of Gluon Shadowing and Antishadowing on J/ψ Production in dAu Collisions at {\sqrt{s} = 200} GeV

We have carried out a wide study of shadowing and antishadowing effects on J/ψ production in dAu collisions at ${\sqrt{s_{N N}} = 200}$ GeV. We have studied the effects of three different gluon nPDF sets, using the exact kinematics for a 2 → 2 process, namely g +?g → J/ψ?+?g as expected from LO pQCD. We have computed the rapidity dependence of R _CP and R _dAu for the different centrality classes of the PHENIX data. For mid rapidities, we have also computed the transverse-momentum dependence of the nuclear modification factor, which cannot be predicted with the usual 2 → 1 simplified kinematics. All these observables have been compared to the PHENIX data in dAu collisions.     

Atomic—Scale Kinetic Monte Carlo Simulation of {100}—Oriented Diamond Film Growth in C—H and C—H—CI Systems by Chemical Vapour Deposition

We simulate the {100}-oriented diamond film growth of chemical vapour deposition (CVD) under different models in C-H and C-H-Cl systems in an atomic scale by using the revised kinetic Monte Carlo method.The simulation results show that:(1) the CVD diamond film growth in the C-H system is suitable for high substrate temperature,and the film surface roughness is very coarse;(2) the CVD diamond film can grow in the C-H-Cl system either at high temperature or at low temperature,and the film quality is outstanding;(3) atomic Cl takes an active role for the growth of diamond film,especially at low temperatures.The concentration of atomic Cl should be controlled in a proper range.     

Measurement of the spin-correlation coefficients A x,x and A y,y in the quasi-free np → {pp} s π− reaction near threshold at ANKE-COSY

A kinematically complete double-polarization measurement of the quasi-free np → {pp} _s π^? reaction near threshold has been performed using the ANKE spectrometer at COSY-Jülich. Here {pp} _s represents a two-proton system with an excitation energy less than 3 MeV. The transversely vector polarized deuteron beam and the internal polarized ANKE hydrogen target were used to determine the spin-correlation coefficients A _x,x and A _y,y . Events from the quasi-free np → dπ⁰ reaction were recorded simultaneously and used for both beam and target polarimetry. In addition, the product of the beam and target polarizations could be estimated from the A _y,y coefficient. The storage cell within the polarized target was the main source of background events. Dedicated runs, with no gas in the cell and with the cell filled with N ₂ gas, were taken to study the backgrounds. The data analysis procedure and the initial results of the experiment are presented.     

An Analysis of Vibrations and Rotations in the First Hydrogen Sulfide Hexade: the 4ν2 H $$_{2}^{{32}}$$ S Band

Optics and Spectroscopy - The infrared spectrum of the H2S molecule is recorded using a Bruker IFS 125HR Fourier transform spectrometer and studied in the range of 4500–5000 cm–1, in...     

PHENIX study of dihadron Δη correlation in Au + Au collision at ?{sNN }sqrt {s_{NN} } = 200 GeV: the ridge

We show the recent study of the ridge phenomena by PHENIX Collaboration over a broad transverse momentum (p _T ) range. Properties of the ridge are extracted in terms of its shape in Δϕ and Δη, and its yield. These properties are found to be similar to the away-side modification in the same p _T range, suggesting a related modification mechanisms in both the near- and away-side.     

PHENIX study of dihadron correlation in Au+Au collision at ?{sNN } \sqrt {s_{NN} } = 200 GeV: jet quenching and medium response

We provide a detailed survey study of dihadron azimuthal angle (Δϕ) correlations in a broad range of transverse momentum (0.4 < p _T < 10 GeV/c) and centrality (0–92%) in Au+Au collisions at 149-2 = 200 GeV. The evolution of the jet shape and yield with p _T seems to suggest two distinct components at the away-side pairs: a suppressed jet fragmentation component around Δϕ ∼ π, and a medium-induced components around |Δϕ − π| ∼ 1.1. The former dominates p _T > 5 GeV/c and the later dominates at p _T < 4 GeV/c.     

Measurement of π0 and η mesons with PHENIX in ?[`(sNN )]\surd \overline {s_{NN} } 200 GeV Au+Au collisions at RHIC

The π ^o meson has been a crucial probe for observing jet quenching in ultrarelativistic heavy-ion collisions at RHIC. Measurements of the η meson in the same collisions have also shed light on a possible dependence of the observed suppression on the particle species. The preliminary π ⁰ nuclear modification factor R _AA from the 2004 RHIC run allowed a first systematic comparison between a precise measurement with high statistics and theoretical calculations, constraining model parameters such as the initial gluon density dN^g/dy, and the transport coefficient [^(q)]\hat q. The final π ⁰ spectra and R _AA are shown as well as the first η results obtained with both PHENIX electromagnetic calorimeters.     

Measurement of the mass and width of the W boson in e+e- collisions at ?s\sqrt{s} = 161–209 GeV

A measurement of the W boson mass and width has been performed by the DELPHI collaboration using the data collected during the full LEP2 programme (1996–2000). The data sample has an integrated luminosity of 660 pb^-1 and was collected over a range of centre-of-mass energies from 161 to 209 GeV. Results are obtained by applying the method of direct reconstruction of the mass of the W from its decay products in both the W⁺W^-→ℓν̄_ℓqq̄’ and W⁺W^-→qq̄’q̄q’ channels. The W mass result for the combined data set is where FSI represents the uncertainty due to final state interaction effects in the qq̄’q̄q’ channel, and LEP represents that arising from the knowledge of the collision energy of the accelerator. The combined value for the W width is These results supersede all values previously published by the DELPHI collaboration. This paper is dedicated to the memory of Carlo Caso.