In the context of future electron-ion collision experiments,particularly the Electron-Ion Collider(EIC)and the Electron-Ion Collider in China(EicC),investigating exclusive photoproduction processes is of paramount imp...In the context of future electron-ion collision experiments,particularly the Electron-Ion Collider(EIC)and the Electron-Ion Collider in China(EicC),investigating exclusive photoproduction processes is of paramount importance.These processes offer a distinctive opportunity to probe the gluon structure of nuclei across a broad range of Bjorken x,thereby enabling measurements of nuclear shadowing and facilitating the search for gluon saturation and color glass condensates.This study explores the potential of utilizing neutron tagging via the Coulomb excitation of nuclei to precisely determine the impact parameter for exclusive photoproduction in electron-ion collisions.By developing the equivalent photon approximation for fast electrons,this study incorporates a coordinate-space-dependent photon flux distribution to elucidate the relationship between the photon transverse momentum distribution and the collision impact parameter.Furthermore,the differential cross section for Coulomb excitation of nuclei is derived by leveraging the spatial information from the photon flux.Our calculations demonstrate that neutron tagging can significantly alter the impact parameter distributions,thereby providing a robust method for impact parameter manipulation in electron-ion collisions.This study provides valuable insights and strategies for exploring the impact parameter dependence of exclusive photoproduction,offering novel insights for experimental design and data analysis.Ultimately,it enhances our understanding of the gluon distribution within the nucleus.展开更多
Carbon monoxide(CO) plays a significant role in global warming and atmospheric chemistry. Global oceans are net natural sources of atmospheric CO. CO at surface ocean is primarily produced from the photochemical degra...Carbon monoxide(CO) plays a significant role in global warming and atmospheric chemistry. Global oceans are net natural sources of atmospheric CO. CO at surface ocean is primarily produced from the photochemical degradation of chromophoric dissolved organic matter(CDOM). In this study, the effects of photobleaching, temperature and the origin(terrestrial or marine) of CDOM on the apparent quantum yields(AQY) of CO were studied for seawater samples collected from Jiaozhou Bay. Our results demonstrat that photobleaching, temperature and the origin of CDOM strongly affected the efficiency of CO photoproduction. The concentration, absorbance and fluorescence of CDOM exponentially decreased with increasing light dose. Terrestrial riverine organic matter could be more prone to photodegradation than the marine algae-derived one. The relationships between CO AQY and the dissolved organic carbon-specific absorption coefficient at 254 nm for the photobleaching study were nonlinear, whereas those of the original samples were strongly linear. This suggests that: 1) terrestrial riverine CDOM was more efficient than marine algae-derived CDOM for CO photoproduction; 2) aromatic and olefinic moieties of the CDOM pool were affected more strongly by degradation processes than by aliphatic ones. Water temperature and the origin of CDOM strongly affected the efficiency of CO photoproduction. The photoproduction rate of CO in autumn was estimated to be 31.98 μmol m-2 d-1 and the total DOC photomineralization was equivalent to 3.25%- 6.35% of primary production in Jiaozhou Bay. Our results indicate that CO photochemistry in coastal areas is important for oceanic carbon cycle.展开更多
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 ...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).展开更多
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...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.展开更多
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...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.展开更多
With a photon spectrum of high energy charged partons, both differential and total cross sections of J/ψ√andΥ(1s) inclusive photoproduction in ultra-peripheral p-Pb Collisions (UPCs) at s=5.5 Te V are given. A dire...With a photon spectrum of high energy charged partons, both differential and total cross sections of J/ψ√andΥ(1s) inclusive photoproduction in ultra-peripheral p-Pb Collisions (UPCs) at s=5.5 Te V are given. A direct photon process and a resolved photon process including fragment and non-fragment contributions are considered. The total cross section is compared to the inelastic production results in coherent p-Pb collisions at the same center-of-mass energy. Our results seem non-negligible.展开更多
Fluctuations of dilepton production from two photon interactionsγγ→l^+l^-are studied in semicentral and peripheral nuclear collisions.Based on the Weizsacker-Williams approach,electromagnetic(EM)fields generated by...Fluctuations of dilepton production from two photon interactionsγγ→l^+l^-are studied in semicentral and peripheral nuclear collisions.Based on the Weizsacker-Williams approach,electromagnetic(EM)fields generated by moving nuclear charges are approximated as quasi-real photons.As fluctuating EM fields in each collision event are hard to be measured directly in experiments due to its short lifetime,we study the dilepton photoproduction with fluctuating EM fields,which are crucial for the EM fields induced chiral and charged particle evolutions,and calculate the relative standard deviation of the dilepton mass spectrum with the event-by-event fluctuating nuclear charge distributions.This fluctuation effect becomes smaller in more peripheral collisions where the shift of proton positions is implicit for EM fields outside the nucleus.The uncertainty of effective impact parameter△b on the standard deviation is also studied,and its effect is around one-third of the effect of nuclear charge fluctuations when△b is taken as^1 fm.展开更多
Based on the quark-gluon contents of nucleon and strongly believing that the force mediators,Pomeronand its counterpart in the conventional approach of Regge theory,for high energy diffractive process would be the ten...Based on the quark-gluon contents of nucleon and strongly believing that the force mediators,Pomeronand its counterpart in the conventional approach of Regge theory,for high energy diffractive process would be the tensorglueball and Odderon respectively,we discuss photo-production of vector meson φ off the deuteron at energy less than 3GeV in the QCD inspired model in which the quark gluon degrees of freedom and glueball,Odderon exchange are takeninto account.A calculation is performed for γ + D →φ + D,and the theoretical predictions of the differential crosssection dσ^(γD)) /dt,are presented and compared with available experimental data.Our QCD inspired model reproducesdata quite well in the whole range of the experimental measurements up to |t| ■0.4 GeV.Our results can be used toextract γn→φn data,which cannot be measured in experiment.展开更多
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 calcula...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.展开更多
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 ...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.展开更多
We study the inelastic charmonium(J/ψ,ψ(2S))and bottomonium(Υ(nS))photoproduction and fragmentation processes in p-p and Pb-Pb collisions at LHC energies,where the ultra-incoherent photon emission is included.Using...We study the inelastic charmonium(J/ψ,ψ(2S))and bottomonium(Υ(nS))photoproduction and fragmentation processes in p-p and Pb-Pb collisions at LHC energies,where the ultra-incoherent photon emission is included.Using the NRQCD factorization approach,an exact treatment is developed.This approach recovers the Weizs?cker-Williams approximation(WWA)near the Q^(2)~0region,where the Martin-Ryskin and BCCKL methods are used to avoid double counting.We calculated the Q^(2),y,z,√s and p_(T)dependent and total cross sections.Inelastic photoproduction and fragmentation were observed to contribute to heavy quarkonium production,particularly at large p_(T).In addition,the contribution of the ultra-incoherent photon channel,which increases rapidly with quarkonium mass,is significant and begins to dominate the photoproduction processes for large p_(T).We also obtained the complete WWA validity scopes of inelastic heavy quarkonium photoproduction in heavy-ion collisions.The WWA had high accuracy at high energies and for Pb-Pb collisions.However,current photon spectra are derived beyond the WWA scope,and double counting can occur when considering different channels simultaneously.展开更多
We present a comprehensive analysis of near-threshold photoproduction ofρ^(0),ω,andΦmesons on a deuterium target,utilizing published datasets from DESY and SLAC forρ^(0)andωproduction,as well as data from the LEP...We present a comprehensive analysis of near-threshold photoproduction ofρ^(0),ω,andΦmesons on a deuterium target,utilizing published datasets from DESY and SLAC forρ^(0)andωproduction,as well as data from the LEPS and CLAS Collaborations forΦproduction.In extracting the deuteron mass radius,we adopt a dipole parameterization for the scalar gravitational form factor,which effectively captures the|t|-dependence of the differential cross sections associated with vector meson photoproduction.In addition,results from alternative commonly used form factor parameterizations are considered and compared.By employing the vector meson dominance(VMD)framework and invoking low-energy Quantum Chromodynamics(QCD)theorems,we extract the deuteron mass radius from near-threshold photoproduction data ofρ^(0),ω,andΦmesons.The mass radii obtained from the various datasets are found to be consistent within statistical uncertainties,yielding an average value of 2.03±0.13 fm under the dipole form assumption.We also provide a detailed discussion of the sensitivity of the extracted radius to the choice of gravitational form factor models.Our result represents a significant improvement in precision compared to earlier estimates based solely onΦmeson photoproduction,offering new constraints for theoretical models of nuclear structure and deepening our understanding of the mass distribution within the deuteron.展开更多
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 ter...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.展开更多
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...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.展开更多
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 n...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.展开更多
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 expe...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.展开更多
Based on low energy QCD Lagrangian, and using wave function of baryon in [SuSF(6)? 0(3)]sym.? Suc(3) quark model, strange meson photoproduction off the proton is studied. Calculations of cross sections and p-polarizat...Based on low energy QCD Lagrangian, and using wave function of baryon in [SuSF(6)? 0(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 + + Λ 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.展开更多
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 a...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.展开更多
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...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.展开更多
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 ...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.展开更多
基金supported in part by the National Key Research and Development Program of China under Contract No.2022YFA1604900the National Natural Science Foundation of China(NSFC)under Contract No.12175223 and 12005220+1 种基金W.Zha is supported by Anhui Provincial Natural Science Foundation No.2208085J23Youth Innovation Promotion Association of Chinese Academy of Science.
文摘In the context of future electron-ion collision experiments,particularly the Electron-Ion Collider(EIC)and the Electron-Ion Collider in China(EicC),investigating exclusive photoproduction processes is of paramount importance.These processes offer a distinctive opportunity to probe the gluon structure of nuclei across a broad range of Bjorken x,thereby enabling measurements of nuclear shadowing and facilitating the search for gluon saturation and color glass condensates.This study explores the potential of utilizing neutron tagging via the Coulomb excitation of nuclei to precisely determine the impact parameter for exclusive photoproduction in electron-ion collisions.By developing the equivalent photon approximation for fast electrons,this study incorporates a coordinate-space-dependent photon flux distribution to elucidate the relationship between the photon transverse momentum distribution and the collision impact parameter.Furthermore,the differential cross section for Coulomb excitation of nuclei is derived by leveraging the spatial information from the photon flux.Our calculations demonstrate that neutron tagging can significantly alter the impact parameter distributions,thereby providing a robust method for impact parameter manipulation in electron-ion collisions.This study provides valuable insights and strategies for exploring the impact parameter dependence of exclusive photoproduction,offering novel insights for experimental design and data analysis.Ultimately,it enhances our understanding of the gluon distribution within the nucleus.
基金financially supported by the National Natural Science Foundation of China (No. 40976043)the Science and Technology Key Project of Shandong Province (2006GG2205024)+2 种基金the Changjiang Scholars Program, Ministry of Education of Chinathe Taishan Scholars Program of Shandong Provincethe Scholar Foundation of Qingdao Agricultural University (631102)
文摘Carbon monoxide(CO) plays a significant role in global warming and atmospheric chemistry. Global oceans are net natural sources of atmospheric CO. CO at surface ocean is primarily produced from the photochemical degradation of chromophoric dissolved organic matter(CDOM). In this study, the effects of photobleaching, temperature and the origin(terrestrial or marine) of CDOM on the apparent quantum yields(AQY) of CO were studied for seawater samples collected from Jiaozhou Bay. Our results demonstrat that photobleaching, temperature and the origin of CDOM strongly affected the efficiency of CO photoproduction. The concentration, absorbance and fluorescence of CDOM exponentially decreased with increasing light dose. Terrestrial riverine organic matter could be more prone to photodegradation than the marine algae-derived one. The relationships between CO AQY and the dissolved organic carbon-specific absorption coefficient at 254 nm for the photobleaching study were nonlinear, whereas those of the original samples were strongly linear. This suggests that: 1) terrestrial riverine CDOM was more efficient than marine algae-derived CDOM for CO photoproduction; 2) aromatic and olefinic moieties of the CDOM pool were affected more strongly by degradation processes than by aliphatic ones. Water temperature and the origin of CDOM strongly affected the efficiency of CO photoproduction. The photoproduction rate of CO in autumn was estimated to be 31.98 μmol m-2 d-1 and the total DOC photomineralization was equivalent to 3.25%- 6.35% of primary production in Jiaozhou Bay. Our results indicate that CO photochemistry in coastal areas is important for oceanic carbon cycle.
基金Supported by the National Natural Science Foundation of China under Grant No.11847207the International Postdoctoral Exchange Fellowship Program of China under Grant No.20180010the China Postdoctoral Science Foundation funded project No.2017M610663
文摘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).
文摘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.
文摘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.
基金Supported by the National Natural Science Foundation of China under Grant Nos.11465021,11065010
文摘With a photon spectrum of high energy charged partons, both differential and total cross sections of J/ψ√andΥ(1s) inclusive photoproduction in ultra-peripheral p-Pb Collisions (UPCs) at s=5.5 Te V are given. A direct photon process and a resolved photon process including fragment and non-fragment contributions are considered. The total cross section is compared to the inelastic production results in coherent p-Pb collisions at the same center-of-mass energy. Our results seem non-negligible.
基金supported by NSFC Grant No.11705125,11547043the Sino-Germany(CSC-DAAD)Postdoc Scholarshipsupport by the AI grant of SAMSON AG,Frankfurt.
文摘Fluctuations of dilepton production from two photon interactionsγγ→l^+l^-are studied in semicentral and peripheral nuclear collisions.Based on the Weizsacker-Williams approach,electromagnetic(EM)fields generated by moving nuclear charges are approximated as quasi-real photons.As fluctuating EM fields in each collision event are hard to be measured directly in experiments due to its short lifetime,we study the dilepton photoproduction with fluctuating EM fields,which are crucial for the EM fields induced chiral and charged particle evolutions,and calculate the relative standard deviation of the dilepton mass spectrum with the event-by-event fluctuating nuclear charge distributions.This fluctuation effect becomes smaller in more peripheral collisions where the shift of proton positions is implicit for EM fields outside the nucleus.The uncertainty of effective impact parameter△b on the standard deviation is also studied,and its effect is around one-third of the effect of nuclear charge fluctuations when△b is taken as^1 fm.
基金Supported by National Natural Science Foundation of China under Grant Nos.10647002 and 10565001
文摘Based on the quark-gluon contents of nucleon and strongly believing that the force mediators,Pomeronand its counterpart in the conventional approach of Regge theory,for high energy diffractive process would be the tensorglueball and Odderon respectively,we discuss photo-production of vector meson φ off the deuteron at energy less than 3GeV in the QCD inspired model in which the quark gluon degrees of freedom and glueball,Odderon exchange are takeninto account.A calculation is performed for γ + D →φ + D,and the theoretical predictions of the differential crosssection dσ^(γD)) /dt,are presented and compared with available experimental data.Our QCD inspired model reproducesdata quite well in the whole range of the experimental measurements up to |t| ■0.4 GeV.Our results can be used toextract γn→φn data,which cannot be measured in experiment.
基金Supported by the National Natural Science Foundation of China under Grant Nos 11065010 and 11465021
文摘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.
文摘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.
基金Supported in part by the National Natural Science Foundation of China(12305092,12233006,12150013)the Xingdian Talent Support Program for Youth Project+1 种基金by the Yunnan Fundamental Research Projects(202401AU070206)supported by the Scientific Research and Innovation Project of Postgraduate Students in the Academic Degree of Yun Nan University(KC-242410212)。
文摘We study the inelastic charmonium(J/ψ,ψ(2S))and bottomonium(Υ(nS))photoproduction and fragmentation processes in p-p and Pb-Pb collisions at LHC energies,where the ultra-incoherent photon emission is included.Using the NRQCD factorization approach,an exact treatment is developed.This approach recovers the Weizs?cker-Williams approximation(WWA)near the Q^(2)~0region,where the Martin-Ryskin and BCCKL methods are used to avoid double counting.We calculated the Q^(2),y,z,√s and p_(T)dependent and total cross sections.Inelastic photoproduction and fragmentation were observed to contribute to heavy quarkonium production,particularly at large p_(T).In addition,the contribution of the ultra-incoherent photon channel,which increases rapidly with quarkonium mass,is significant and begins to dominate the photoproduction processes for large p_(T).We also obtained the complete WWA validity scopes of inelastic heavy quarkonium photoproduction in heavy-ion collisions.The WWA had high accuracy at high energies and for Pb-Pb collisions.However,current photon spectra are derived beyond the WWA scope,and double counting can occur when considering different channels simultaneously.
基金Supported by the National Natural Science Foundation of China(12305127)the International Partnership Program of the Chinese Academy of Sciences(016GJHZ2022054FN)National Key R&D Program of China(2024YFE0109800,2024YFE0109802)。
文摘We present a comprehensive analysis of near-threshold photoproduction ofρ^(0),ω,andΦmesons on a deuterium target,utilizing published datasets from DESY and SLAC forρ^(0)andωproduction,as well as data from the LEPS and CLAS Collaborations forΦproduction.In extracting the deuteron mass radius,we adopt a dipole parameterization for the scalar gravitational form factor,which effectively captures the|t|-dependence of the differential cross sections associated with vector meson photoproduction.In addition,results from alternative commonly used form factor parameterizations are considered and compared.By employing the vector meson dominance(VMD)framework and invoking low-energy Quantum Chromodynamics(QCD)theorems,we extract the deuteron mass radius from near-threshold photoproduction data ofρ^(0),ω,andΦmesons.The mass radii obtained from the various datasets are found to be consistent within statistical uncertainties,yielding an average value of 2.03±0.13 fm under the dipole form assumption.We also provide a detailed discussion of the sensitivity of the extracted radius to the choice of gravitational form factor models.Our result represents a significant improvement in precision compared to earlier estimates based solely onΦmeson photoproduction,offering new constraints for theoretical models of nuclear structure and deepening our understanding of the mass distribution within the deuteron.
基金Partially supported by the National Natural Science Foundation of China(12175240,12147153,11635009,12305097,12305137)the Fundamental Research Funds for the Central Universitiesthe China Postdoctoral Science Foundation(2021M693141,2021M693142)。
文摘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.
基金Supported by Schweizerischer Nationalfonds and Deutsche Forschungsgemeinschaft (SFB/TR-16)
文摘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.
文摘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.
基金Supported by the National Natural Science Foundation of China (12005220, 12175223)MOST (2018YFE0104900)
文摘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.
基金The work was supported in part by the National Natural Science Foundation of China ( Grant Nos. 19975053, 19835010, 10075081 and 19905011).
文摘Based on low energy QCD Lagrangian, and using wave function of baryon in [SuSF(6)? 0(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 + + Λ 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.
基金Supported by German Science Foundation (DFG) in the frame ot the SFB/TR-16
文摘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.
基金Supported by German Science Foundation (DFG) in the frame of the SFB/TR16
文摘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.
文摘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.
