Search

LHC provides a chance to study the physical processes of γγ collision and γ p collision mode by adding a forward detector. In this paper, we investigate J/ψ-pair photoproduction in NRQCD framework at the LHC with γγ collision mode. We calculate the contributions from 3 S 1 1 , 3 S 1 (8) , 1 S 0 (8) , 3 P J (8) Fock states, and find that contribution from the colour octet 1 S 0 8 3 P J (8) and 3 P J (8) 3 P J (8) channels dominates this process with forward detector acceptance 0.0015 < ξ < 0.5. We present the differential cross section distributions of transverse momentum p t J / ψ and rapidity yJ/ψ with forward detector acceptances 0.0015 < ξ < 0.5, analyse the signal for J/ψ decaying to a opposite-sign (OS) muon pair. The results show that this process has the potential to be detected at the 13 TeV LHC with forward detector acceptance 0.0015 < ξ < 0.5. [ABSTRACT FROM AUTHOR]

Formaldehyde (HCHO) is an important component in tropospheric chemistry, but the study of HCHO in rainwater is limited. This is the first report of continuous measurement of HCHO in rainwater. HCHO in rainwater was continuously measured using a modified chemiluminescence method at Sakai City, Osaka, Japan. The continuous measurement was conducted in the 2018 rainy season (Baiu) of Japan. A total of 20 rain events have been observed, and the averaged HCHO concentration of each rain event was 0.13–2.75 μM. The maximum concentration was 9.91 μM. Diurnal variation of HCHO in rainwater showed the distinctively high concentration in nighttime and no correlation with local ambient gaseous HCHO, implying another source such as aqueous photoproduction and transportation rather than scavenging. The photo-irradiation experiment revealed that photoproduction of HCHO is one of the important sources of HCHO in rainwater with the maximum production rate of 2.43 μM h−1. Besides, the backward trajectory indicated that there could have a link with the air mass original location. Furthermore, microorganism activity can play a role as a sink of HCHO in rainwater that could consume HCHO with digestion rate up to 3.2 μM h−1. [ABSTRACT FROM AUTHOR]

In spite of a large amount of the existing experimental data in the region of low-energy proton- and photon-nuclear interactions, new experimental measurements are still needed to gain insight into a number of problems in nuclear physics. Particularly, the stellar nucleo-synthesis, the study of the resonance states of light nuclei, the underlying mechanisms of the (p,n), (p,α) and (γ,p), (γ,n) reactions are of great interest. For this purpose, the possibility of exploitation of existing electron linear accelerator and cyclotron C18/18, which was launch out recently at AANL (Yerevan Physics Institute), are discussed. The upgrade of the existing electron machine and the purchase of a new modern one for the study of the aforementioned nuclear physics problems are presented as well. [ABSTRACT FROM AUTHOR]

Experimental results on quasielastic photoproduction of the ρ meson in association with a neutron, obtained at the HERA collider, are presented. The total and differential cross sections of the γ p → ρ nπ reaction at the positron-proton center-of-mass energy of √s =319 GeV are measured. The data collected with the H1 detector in 2006 and 2007 correspond to an integrated luminosity of 1.16 pb. The kinematic region of the photon-proton cms energy of 20 < W <100 GeV, photon virtuality of Q < 2 GeV, and the ρ transverse momentum below 1 GeV/ c is analyzed. Secondary neutrons with energies x > 0.35 (in proton-energy units) and emission angles below 0.75 mrad are selected. The model of double peripheral exchange, in which the ρ is elastically produced via the photon interaction with the virtual pion from the proton-neutron vertex, is employed for interpreting the results. The cross section for the ρ elastic photoproduction on the pion, γπ→ ρπ, is extracted in the one-pion-exchange approximation. The magnitude of the cross section suggests that the γ p → ρ nπ reaction is significantly affected by absorption. [ABSTRACT FROM AUTHOR]

Sediments exposed to simulated solar radiation can serve as an important source of dissolved organic carbon (DOC) to surrounding waters. However, it is still unclear if dissolved nutrients can be photoproduced from lake sedimentary organic matter. In this study, a series of laboratory-based experiments was conducted to address the photoproduction of dissolved inorganic nutrients and DOC from resuspended Taihu Lake sediments. Dissolved inorganic nutrients and DOC were photoproduced after 8-h irradiation. The released NH , NO , and DOC levels ranged from 3.57 to 12.14, 1.43 to 6.43, and 24.17 to 69.17 μmol L, respectively. The variation in the amount released indicated that sediment source had an effect on DOC and nutrient photorelease. More DOC and nutrients were released from higher concentration suspensions. However, due to the light absorption by suspended sediment, less DOC and nutrients were released from per gram of suspended sediment in high concentration suspensions. The decrease in DOC and increase in dissolved inorganic nitrogen during the last 2-h irradiation indicated that the photoproduction of inorganic nutrients proceeded via direct photodissolution of suspended sediments and subsequent photodegradation of the produced dissolved organic matter. Our results demonstrated that the photoproduction flux of NH and NO accounts for 12.3 and 6.5 % of wet deposition, respectively, which suggest that the photodissolution of suspended sediment could be a potential source of DOC and dissolved nutrients in shallow water ecosystems. [ABSTRACT FROM AUTHOR]

Methodological part of analysis of the coherent photoproduction of a proton-antiproton pair based on experimental data obtained at CLAS facility of the Jefferson Linear Accelerator Laboratory (USA) is represented. The beam of tagged photons with energies up to 5.75 GeV used in the experiment was incident on 40 cm long liquid deuterium target. The description of methods for identification of multiparticle final states in completely exclusive reactions is given. It is shown how the kinematics of coherent photoproduction of $$\gamma \bar p$$, ππ, k k pairs was used for identification of final state particles and reactions. [ABSTRACT FROM AUTHOR]

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 d 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. [ABSTRACT FROM AUTHOR]

Neutron-proton pair knocking-out by photons from iron (Fe) nuclei is studied by measuring induced gamma activity of Mn isotope. Experiments are performed in a synchrotron beam at two maximum photon energies, 150 and 650 MeV. It was found that the yield of the reaction under study at the maximum energy of 150 MeV is almost zero, whereas a significant yield of gamma active Mn nuclei is measured at the energy of 650 MeV. The cross section of the neutron-proton pair production reaction on Fe at an energy of 650 MeV is estimated as 4 · 10 cm. [ABSTRACT FROM AUTHOR]

The results of phenomenological partial-wave analysis of angular distributions for the process γ p → ν p measured at the Tohoku University (Japan) and model-independent estimates of Breit-Wigner parameters of S11(1535) and S11(1650) nucleon resonances obtained based on these data are presented. [ABSTRACT FROM AUTHOR]

The article reports on the quantitation of hydroxyl radicals from photolysis of Fe(III)-citrate complexes in aerobic water. Fe(III)-citrate complexes are important sources of OH radicals for some atmospheric and surface waters. Photolysis of Fe(III)-citrate complexes in the presence of oxygen play an important role in producing OH in atmospheric waters and surface waters where high concentrations of citrate ions and ferric ions exist. Photoproduction of OH has a high oxidizing potential for the degradation of a wide variety of natural and anthropogenic inorganic and organic substances.

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. [ABSTRACT FROM AUTHOR]

The photon remnant was studied within Monte Carlo models PYTHIA, HERWIG and RAPGAP in resolved photo- and low-Q2 production. The Monte Carlo models differ significantly in the modelling of the photon remnant. [ABSTRACT FROM AUTHOR]

Rhodobacter sphaeroides photoproduced indole 3-acetic acid (IAA) when the precursor L-tryptophan was added to the basal medium. Of the other organic carbon sources that influenced IAA formation from L-tryptophan, α-ketoglutaric acid gave the maximum formation of 530 mg 1−1 in less than 24 h of illuminated anaerobic incubation. IAA was also produced from indole, glycine and glucose together by Rb. sphaeroides under photoanaerobic conditions yielding 61 mg l−1 within 30 fh. [ABSTRACT FROM AUTHOR]

Axenic culture of photosynthetic purple sulphur bacterium, isolated from a paper mill effluent, grew best with ammonium chloride as nitrogen source. Cells grown with N or ammonium chloride produced hydrogen with initial lag periods of 24 and 48 h, respectively. The maximum amount of hydrogen was evolved by cells grown with N and with malate as electron donor. [ABSTRACT FROM AUTHOR]

The exclusive photoproduction of Υ (nS) meson states from protons, γ p → Υ (nS) p (with n = 1 , 2 , 3 ), is studied in ultraperipheral p Pb collisions at a centre-of-mass energy per nucleon pair of s NN = 5.02 TeV . The measurement is performed using the Υ (nS) → μ + μ - decay mode, with data collected by the CMS experiment corresponding to an integrated luminosity of 32.6 nb - 1 . Differential cross sections as functions of the Υ (nS) transverse momentum squared p T 2 , and rapidity y, are presented. The Υ (1 S) photoproduction cross section is extracted in the rapidity range | y | < 2.2 , which corresponds to photon–proton centre-of-mass energies in the range 91 < W γ p < 826 GeV . The data are compared to theoretical predictions based on perturbative quantum chromodynamics and to previous measurements. [ABSTRACT FROM AUTHOR]