HYDROGEN PHOTOPRODUCTION OF A.VARIABILIS INCORPORATED IN A PHOTOBIOREACTOR

H2 photoproduction and nitrogenase activities in two strains of Anabaena variabilismarked wild type ATCC 29413 and mutant PK84 exposed to thermal stress (temperature higher than thenormal incubation temperature of 30℃) were studied. Cultures of both strains collected from any intervalof logarithmic growth phase exhibited high H2 photoproduction and nitrogenase activities when exposed tolimited time heat shock during the assay process. In contrast, the algal H2 photoproduction rate of bothstrains fluctuated with long term thermal stress caused hy increasing the growth temperature from 30℃ to36℃.The changes of nitrogenase (the key H2 photobiosynhetic enzyme) activities in the mutant PK84showed variation tendency similar to that of H2 photoproduction during exposure to thermal stress, indicat-ing that fluctuation of H2 photopnduction in the mutant was mainly due to the variation of nitrogenase ac-tivities. A temporary maximal H2 photoproduction in the mutant PK84 (wild type ATCC29413 ) was ob-served when cells po at 36℃ for 14 (6) days. However, the responses of nitrogenase activities in thewild type to thermal stress were not completely similar to those in the mutant in spite of similar variationsof H2 photoproduction in both strains. The data obtained in these studies suggested tha the activities ofother enzymes (in the wild strain) involved in H2 photoproduction were affected by thermal stress since H2photoporduction maximized or dropped to 0 without variation tendency similar to that of nitrogenase activi-ties.Furthermore, an enhancement of H2 photoproduction speed of the mutant strain cultured in a 4.4 Llaboratory photobioreactor was also observed when it was subjected to short time continuous charge of ar-gon, and temperature rise.All these results indicated that high temperature plays an important role in the photo-autotrophic H2photoproduction, and that long term thermal stress is unfavourable for net H2 phooproduction in bothstrains of A. variabilis though short-time heat shock is conducive to H2 photoproduction.

Production of High-p_T Kaon and Pion in PP and Au-Au Collisions by Resolved Photoproduction Processes

Taking into account the effects of shadowing and jet quenching, the large transverse momentum distribution of K＋, π＋ and K＋/π＋ ratios at s = 200 GeV originating from resolved photoproduction processes is calculated based on perturbative quantum chromodynamics. It is found that the contribution of K＋ and π＋ produced by photoproduction processes is evident. The K＋ /π＋ ratios in Au-Au collisions show an obvious enhancement compared with p p collisions. The numerical results indicate that the photoproduetion processes are good modification for kaon and pion production.

J/ψ and T Photoproduction at LHC

Hard photoproduction of J/ψ and T at large hadron collider(LHC)Pb-Pb collisionswith CMS energy 6300 GeV/u is discussed in the process Pb+Pb→Pb+J/ψ+X with threetypes of equivalent photon spectrum functions.It turns out that the hard photoproductionprocesses can be used to probe several important problems such as the gluon distribution in thenucleus,gluon and heavy q.uark fragmentation of J/ψ,et al.In addition,the process alsoprovides a new way of testing the EMC effects.

Analysis of data for γp → f1(1285)p photoproduction

The photoproduction of the f1(1285)meson off the proton target is investigated within an effective Lagrangian approach.The t-channelρ-andω-exchange diagrams,u-channel nucleon-exchange diagram,generalized contact term,and s-channel pole diagrams of the nucleon and a minimal number of nucleon resonances are taken into account in constructing the reaction amplitudes to describe the experimental data.Three different models,that is,the Feynman,Regge,and interpolated Regge models,are employed,where the t-channel reaction amplitudes are constructed in Feynman,Regge,and interpolated Regge types,respectively.The results show that neither the Feynman model with two nucleon resonances nor the interpolated Regge model with one nucleon resonance can satisfactorily reproduce the available data forγp→f1(1285)p.Nevertheless,in the Regge model,when any one of the N(1990)7/2^(+),N(2000)5/2^(+),N(2040)3/2^(+),N(2060)5/2^(-),N(2100)1/2^(+),N(2120)3/2^(-),N(2190)7/2^(-),N(2300)1/2^(+),and N(2570)5/2^(-)resonances is considered,the data can be well described.The resulting resonance parameters are consistent with those advocated in the Particle Data Group(PDG)review.Further analysis shows that,in the high-energy region,the peaks of γp→f1(1285)p differential cross sections at forward angles are dominated by the contributions from t-channelρ-andω-exchange diagrams,while in low-energy region,the s-channel pole diagrams of resonances also provide significant contributions to theγp→f1(1285)p cross sections.

First extraction of the proton mass radius and scattering length |αρ0p|from ρ^(0) photoproduction

As it involves the lightest physical states excited from the vacuum by the vector quark current,near-threshold ρ^(0)photoproduction is considered a possible way to research the proton radius and the absolute value of the scattering lengths of the ρ^(0)-proton interaction.In this study,under the assumption of a scalar form factor of dipole form,the value of the proton mass radius is calculated as(0.85±0.06) fm by fitting the differential cross section of the γp→ρ^(0)p reaction at near-threshold energy.For light vector meson photoproduction,because the exchange of a scalar quark-antiquark pair is not suppressed and should dominate the scalar gluon exchange,the radius we extract from ρ^(0)photoproduction is likely to represent the quark radius of the proton.This fact may explain why the value obtained in this study is very near the proton charge radius.Moreover,the absolute value of the ρ^(0)-proton scattering length |αρ^(0)p|=(0.31±0.06) fm is obtained for the first time within the vector meson dominance model.This result disobeys the rule that the absolute value of the vector meson and proton scattering length |αVp| increases with the meson’s mass,which can be attributed to treating the ρ^(0)meson as a point in the analysis.These results provide useful theoretical information for an in-depth understanding of proton structure and the proton-vector meson interaction.

Gluon gravitational form factors of protons from charmonium photoproduction

Inspired by the recent near-threshold J/ψphotoproduction measurements,we discuss gluon gravitational form factors(GFFs)and internal properties of the proton.This work presents a complete analysis of the proton gluon GFFs connecting the gluon part of the energy-momentum tensor and the heavy quarkonium photoproduction.In particular,a global fitting of the J/ψdifferential and total cross section experimental data is used to determine the gluon GFFs as functions of the squared momentum transfer t.Combined with the quark contributions to the D-term form factor extracted from the deeply virtual Compton scattering experiment,the total D-term is obtained to investigate their applications in describing the proton mechanical properties.These studies provide a unique perspective on investigating the proton gluon GFFs and important information for enhancing QCD constraints on the gluon GFFs.

Photoproduction of mesons off the deuteron:quasifree and coherent processes

Photoproduction of mesons off the deuteron has been investigated at a tagged photon beam of the Bonn ELSA accelerator with the combined Crystal Barrel - TAPS electromagnetic calorimeter for incident photon energies up to 2.5 GeV. The mesons have been detected in coincidence with recoil protons, neutrons and deuterons. This allow the measurement of meson production reactions off the quasifree nucleons bound in the deutron, as well as the coherent production off the deuteron. The comparison of quasifree proton reactions to free proton reactions can confirm or invalidate possible nuclear effects on the extracted cross section reactions. Furthermore the isospin composition of a resonance can be estimated from the comparison of quasifree proton and neutron reactions. The quasifree photoproduction of the η＇ and π°η mesons off nucleons and the coherent photoproduction of π°η--pairs off the deuteron are discussed.

Centrality Dependence of Charmed-Meson Photoproduction in Ultrarelativistic Heavy Ion Collisions

We calculate the centrality dependence of inclusive cross section of large-p _(T )charmed-meson(D^0,D~*,D^(*+),and D_s^+)from heavy quark fragmentation by the hard photoproduction processes in ultrarelativistic heavy ion collisions.The numerical results indicate that the contribution of the hard photoproduction processes cannot be negligible for the inclusive charmed-meson production in Au-Au collisions at Relativistic Heavy Ion Collider(RHIC)and Pb-Pb collisions at Large Hadron Collider(LHC).

A new beam asymmetry measurement from pion photoproduction on the neutron using CLAS

We present a preliminary analysis of the photon beam asymmetry observable （Z） from the pho- toproduction reaction channel γn → pπ in the invariant mass range 1.6--2.3 GeV. The measurement was obtained using the near-4π CEBAF Large Acceptance Spectrometer （CLAS） at Jefferson Laboratory, USA, employing a linearly polarised photon beam with an energy range 1.1 2.3 GeV, incident on a liquid deuterium target. The measurement will provide new data to address the poorly established neutron excitation spectrum and will greatly expand the sparse world data-set both in energy and angle.

Calculations of differential momentum transfer spectra for J/ψphotoproduction in heavy-ion collisions

Understanding the gluonic structure in nuclei is one of the most important goals in modern nuclear physics,for which J/ψphotoproduction is suggested as a powerful tool to probe the gluon density distribution.The experimental investigation of the photoproduction process is conventionally studied in ultra-peripheral heavy-ion collisions,and has recently been extended to hadronic collisions.However,theoretical efforts in hadronic heavy-ion collisions are still lacking in the literature.In this paper,we build up a phenomenological framework to calculate the differential momentum transfer spectra for J/ψphotoproduction in hadronic heavy-ion collisions based on a vector meson dominance model.For the first time,we include the effect of internal photon radiation in the calculations,and we find that the results with internal photon radiation could describe the experimental measurements from STAR very well.

Low energy QCD Lagrangian description of strange meson photoproduction off the proton

Based on low energy QCD Lagrangian, and using wave function of baryon in [SuSF=(6) O(3)]sym.() Suc(3) quark model, strange meson photoproduction off the proton is studied. Calculations of cross sections and p-polarization for γ + p→ K+ + ∧ reaction are performed. The theoretical results show that, compared to traditional phenomenological models, the low energy QCD Lagrangian provides a successful description of the reaction process with only one free parameter, strongly coupling constant αm.

Photoproduction of ω-Mesons at ELSA and the role of azimuthal asymmetries

Measurements of ω photoproduction of the Crystal-Barrel/TAPS experiment at the ELSA accelerator of Bonn University are presented which used linearly polarized tagged photon beam from threshold to Eγ = 1700MeV. The azimuthal asymmetries ∑and ∑πindicate s-channel resonance contributions on top of the established t-channel exchange processes. These findings are further enhanced by a very first measurement of the G-asymmetry which, in addition to the polarized photon beam, also requires a longitudinally polarized proton target. An intuitive interpretation of the specific sensitivity of the azimuthal asymmetries to the reaction mechanisms involved is given.

Photoproduction of multi-meson final states–recent results from the Crystal-Barrel/TAPS experiment at ELSA-

Multi-meson final states such as γp →pπ0π0 and γp →pπ0η have been investigated with the Crystal-Barrel/TAPS experiment at ELSA. Baryon cascades via △π and △η and also via higher mass baryon resonances are clearly observed. Based on this data and on data from other reactions a partial wave analysis has been performed from which partial decay widths of various N＊ and △＊ states into the different pπ0π0 and pπ0η decay channels have been determined, leading partly to unexpected results. In addition, polarisation observables have been investigated. The beam asymmetry X has been determined for both reactions and double polarisation data using a longitudinally polarised target and a circularly or linearly polarised photon beam has been taken. Given the angular coverage of the Crystal-Baxrel/TAPS experiment this data covers almost the full angular range and phase space. This data will provide new and important information for the partial wave analyses and bring us one step closer towards a complete experiment.

Recoil polarimetry in meson photoproduction at MAMI

The nucleon excitation spectrum remains poorly known, with the masses, widths, EM couplings and even existence of many states not well established. A program of experiments using meson photoproduction off the nucleon is being carried out to improve this situation. A new large acceptance recoil polarimeter has been developed by the Edinburgh group for use in such reactions with the Crystal Ball at MAMI. This work summarizes the procedure used to measure recoil polarization with the new device and presents some preliminary results for the double polarization observable Cx in the reaction γp→pπ, compared to the current partial wave analysis.

Photoproduction of J/ψ in non-single-diffractive p+p collisions

Significant enhancements of J/ψ production at very low transverse momenta were recently observed by the ALICE and STAR collaborations in peripheral hadronic A+A collisions. The anomalous excess points to coherent photon-nucleus interactions in violent hadronic heavy-ion collisions, which were conventionally studied only in ultra-peripheral collisions. Assuming that the coherent photoproduction is the underlying mechanism responsible for the excess observed in peripheral A+A collisions, its contribution in p+p collisions with nuclear overlap, i.e. nonsingle-diffractive collisions, is of particular interest. In this paper, we perform a calculation of exclusive J/ψ photoproduction in non-single-diffractive p+p collisions at the RHIC and LHC energies based on the pQCD motivated parametrization using the world-wide experimental data, which could be further employed to improve the precision of the phenomenological calculations for photoproduction in A+A collisions. The differential rapidity and transverse momentum distributions of J/ψ from photoproduction are presented. In comparison with the J/ψ production from hadronic interactions, we find that the contribution of photoproduction is negligible.

Inclusive γ(1S,2S,3S) photoproduction at the CEPC

Inclusive γ(1S,2S,3S) photoproduction at the future Circular-Electron-Positron-Collider(CEPC)is studied,using the non-relativistic quantum chromodynamics(NRQCD)factorization formalism.Including the contributions from both direct and resolved photons,we present different distributions for the γ(1S,2S,3S) production.Our results suggest that there will be considerable events,implying that well measurements of the T photoproduction can be performed to further study heavy quarkonium physics at electron-positron colliders,in addition to hadron colliders.This supplemental study is very important for clarifying the current situation regarding the heavy quarkonium production mechanism.

Coherent photoproduction of J/ψ and γ mesons in pp and PbPb ultraperipheral collisions from dynamical gluon distributions

We present calculations of coherent photoproduction of vector mesons（J/ψ and Υ） with leading-order parton distribution functions to check new kinds of corrections of the DGLAP equations and nuclear modifications.The input gluon distribution of the proton is the dynamical parton model from the DGLAP equations with GLR-MQZRS（Gribov-Levin-Ryskin,Mueller-Qiu,Zhu-Ruan-Shen） modifications.From comparison between several other gluon distribution models,we find that the dynamical gluon distribution fits with the results of meson photoproduction experiments in the high energy region.The calculation of the differential cross sections using dynamical and other gluon distributions is compared with the experimental data from the HERA,ZEUS and LHCb Collaborations.Although there is little data for the rapidity distribution of vector meson photoproduction near zero rapidity,the dynamical gluon distribution works well with the data in the large rapidity region.

Flavor-dependent photoproduction in heavyion collisions

Strong electromagnetic fields produced in the non-central heavy-ion collisions can induce vector meson photoproduction.In this paper,we study the photoproduction J/ψandφmesons in the relativistic heavy-ion collision from ultra-peripheral nuclear collisions to peripheral hadronic heavy ion collisions.And then include both initial hadronic production and thermal production in quark-gluon plasma(QGP).We find,for the charm anti-charm bound state J/ψ,the photoproduced J/ψs are mainly in the very low momentum region and clearly exceed the hadronic production.However,considering the thermal production of strange quark anti-quark pairs in QGP produced in relativistic heavy-ion collisions,the photoproducedφis usually smaller than the thermal production and only evident at very peripheral collisions as even their photoproduction is much larger than J/ψ.

Study of Charged Pion Photoproduction on Deuteron with Tagged Photons

The reactions γd→π-pp and γd→npπ+π-have been studied in an energy range from 0.8 to 1.1 GeV at the tagged photon facility of Laboratory of Nuclear Science,Tohoku University. Charged pions and protons in the final state were measured by using the Neutral Kaon Spectrometer (NKS2). The analysis of the γd→π-pp was mainly used to check the acceptance of the NKS2 and to calibrate the tagged photon energy. The photoproduction of the Δ++Δ-was identified in the γd→npπ+π-reaction. Since the data analyses are still in progress,we issue an interim report and preliminary results.

Reaction dynamics for photoproductions of baryon resonances

The study of exotic structure of hadrons is fully achieved when reaction dynamics of the associated hadron productions is well understood. We employ as the standard mechanism the effective Lagrangian method and investigate several physical observables within the framework. The parameters are constrained by microscopic description of hadrons. We discuss photoproductions of kaon associated with the ground state A（1116） and its resonances A（1405） and A（1520）. In the former example we emphasize the meson cloud effect which significantly renormalizes the phenomenological parameters, while in the latter we discuss the features of the standard method. Finally we discuss briefly the N（1535） for the study of chiral symmetry of baryons. production of ηπ associated with the nucleon resonance