De Production Research Articles

Measurement of prompt [formula omitted]-meson production and azimuthal anisotropy in Pb–Pb collisions at [formula omitted

The production yield and angular anisotropy of prompt Ds+ mesons were measured as a function of transverse momentum (pT) in Pb–Pb collisions at a centre-of-mass energy per nucleon pair sNN=5.02TeV collected with the ALICE detector at the LHC. Ds+ mesons and their charge conjugates were reconstructed at midrapidity (|y|<0.5) from their hadronic decay channel Ds+→ϕπ+, with ϕ→K−K+, in the pT intervals 2<pT<50GeV/c and 2<pT<36GeV/c for the 0–10% and 30–50% centrality intervals. For pT>10GeV/c, the measured Ds+-meson nuclear modification factor RAA is consistent with the one of non-strange D mesons within uncertainties, while at lower pT a hint for a Ds+-meson RAA larger than that of non-strange D mesons is seen. The enhanced production of Ds+ relative to non-strange D mesons is also studied by comparing the pT-dependent Ds+/D0 production yield ratios in Pb–Pb and in pp collisions. The ratio measured in Pb–Pb collisions is found to be on average higher than that in pp collisions in the interval 2<pT<8GeV/c with a significance of 2.3σ and 2.4σ for the 0–10% and 30–50% centrality intervals. The azimuthal anisotropy coefficient v2 of prompt Ds+ mesons was measured in Pb–Pb collisions in the 30–50% centrality interval and is found to be compatible with that of non-strange D mesons. The main features of the measured RAA, Ds+/D0 ratio, and v2 as a function of pT are described by theoretical calculations of charm-quark transport in a hydrodynamically expanding quark–gluon plasma including hadronisation via charm-quark recombination with light quarks from the medium. The pT-integrated production yield of Ds+ mesons is compatible with the prediction of the statistical hadronisation model.

Spectroscopy of the excited Ds mesons

The discoveries of the Ds0*(2317)+ and Ds1(2460)+ mesons challenge our understanding of quantum chromodynamics. After almost 20 years, the nature of these hadrons is still subject of debate and many models have been proposed to explain their unexpected masses: standard charmed-strange mesons, DK molecules and tetraquarks. The LHCb experiment has studied the production of excited Ds+ meson in prompt proton-proton collisions and from b-hadron decays. Precise measurement of their properties and observation of new Ds+ states have been reported. The latest results on the spectroscopy of the charmed-strange mesons and the prospect to investigate their nature will be presented.

Study of tau neutrino production with nuclear emulsion at CERN-SPS

The tau neutrino interaction cross-section was directly measured in the DONuT experiment but it suffers from a large systematic (∼50%) and statistical (∼30%) errors. The main source of the systematic error was due to poor knowledge of the tau neutrino flux. The DsTau experiment at CERN-SPS has been proposed to measure an inclusive differential cross-section of the Ds production with a consecutive decay to tau lepton in p-A interactions, which is a main source of tau neutrinos in neutrino beams at accelerators. The search for Ds → τ → X decay is challenging due to milimetric range of Ds and τ decay lengths and a small angle between them of the order of few mrad. Nevertheless a precise measurement is possible with the use of nuclear emulsion providing a sub-micron spatial resolution. The experiment is aiming to collect 2.3 × 108 proton interactions in the tungsten target, and to detect ∼ 1000 Ds → τ → X decays. DsTau successfully performed a pilot run in 2018 collecting ∼10% of the full data and was approved as NA65 in 2019. The results from the pilot run are presented in this paper and the prospect for physics runs in 2021–2022 are given.

Study of tau neutrino production in proton-nucleus interactions

Tau neutrino properties are not so well known in comparison to those of muon or electron neutrinos. The tau neutrino interaction cross-section was directly measured by the DONUT experiment in 2008 on a basis of 9 registered tau neutrinos, and with a large systematical error of 50% due to a poor knowledge of the tau neutrino flux in this beam dump experiment. However, more accurate measurement of the cross section is needed for future neutrino experiments. It would also allow testing the Lepton Universality (LU) of Standard Model in neutrino interactions. Recently several results for B-meson decays (LHCb, Babar) demonstrated hints of possible LU violation. The tau neutrinos are produced in the Ds meson decays to tau, Ds → τ vT, and the cascade decay of the tau τ → vT X. DsTau experiment has been proposed to study the tau neutrino production at CERN SPS. It will measure the Ds production differential cross-section in the proton-tungsten interactions. This will allow reducing of the uncertainty due to the tau neutrino flux in the DONUT result from 50% to 10%. The peculiar Ds cascade decay topology ("double kink") in a few mm range will be detected by nuclear emulsion tracker thanks to its excellent spatial resolution (∼50nm).In 2016 and 2017, we made test beam exposures of nuclear emulsion modules at CERN SPS 400GeV/c proton beam followed by the pilot run in August 2018. A physics run in 2021 is scheduled. The status and prospects of the DsTau project as well as a review of the modern nuclear emulsion technique and the methods of its data analysis are presented.

Study of radially excited Ds(21S0) and Ds(3P)**Supported by National Natural Science Foundation of China (11475111)

The unobserved JP = 0− radial excitation Ds(21S0) is anticipated to have mass 2650 MeV (denoted as Ds(2650)). Study of hadronic production is an important way to identify highly excited states. We study hadronic production of Ds(2650) from higher excited resonances in a 3P0 model. Relevant hadronic partial decay widths are found to be very small, which implies it is difficult to observe Ds(2650) in hadronic decays of higher excited resonances. Hadronic decay widths of radially excited Ds(3P) have also been estimated. The total decay widths of four Ds(3P) are large, but the branching ratios in the Ds(2650)η channel are very small, which implies that it seems impossible to observe Ds(2650) in hadronic decays of Ds(3P). The dominant decay channels of the four Ds(3P) have been pointed out, and D1(2420), D1(2430), , D(2550), D(2600), (11D2)D(2750) and are possible to observe in hadronic production from Ds(3P).

Measurements of [formula omitted]-meson production in Au + Au collisions at [formula omitted] in STAR

We present the first measurement of the nuclear modification factor RAA and elliptic flow v2 of Ds in Au+Au collisions at sNN=200 GeV with the STAR detector. These results have been compared with those of other open charm mesons and strange mesons to determine how the (possibly) strangeness equilibrated partonic matter affects the Ds meson production. We find that the nuclear modification factor of DS are systematically higher than unity and that of D0. The ratio Ds/D0 is shown as a function of transverse momentum for the 10–40% most central Au+Au collisions and compared with that in p+p collisions obtained from PYTHIA. It is also compared with that in Pb+Pb collisions at 2.76 TeV by the ALICE experiment. Our measurement indicates a hint of enhancement of DS production in Au+Au collisions with respect to p+p collisions as compared to non-strange D mesons.

Evaluation of solar sludge drying alternatives by costs and area requirements

Thermal drying is a common method to reach above 90% dry solids content (DS) in sludge. However, thermal drying requires high amount of energy and can be expensive. A greenhouse solar dryer (GSD) can be a cost-effective substitute if the drying performance, which is typically 70% DS, can be increased by additional heat. In this study feasibility of GSD supported with solar panels is evaluated as an alternative to thermal dryers to reach 90% DS. Evaluations are based on capital and O&M costs as well as area requirements for 37 wastewater treatment plants (WWTPs) with various sludge production rates. Costs for the supported GSD system are compared to that of conventional and co-generation thermal dryers. To calculate the optimal costs associated with the drying system, an optimization model was developed in which area limitation was a constraint. Results showed that total cost was minimum when the DS in the GSD (DSm,i) was equal to the maximum attainable value (70% DS). On average, 58% of the total cost and 38% of total required area were associated with the GSD. Variations in costs for 37 WWTPs were due to differences in initial DS (DSi,i) and sludge production rates, indicating the importance of dewatering to lower drying costs. For large plants, GSD supported with solar panels provided savings in total costs especially in long term when compared to conventional and co-generation thermal dryers.

First Observation of the DecayDs+→pn¯

Using e+e--->Ds*-Ds+ data collected near the peak Ds production energy, Ecm=4170 MeV, with the CLEO-c detector, we present the first observation of the decay Ds+-->pn. We measure a branching fraction B(Ds+-->pn)=(1.30+/-0.36(-0.16)+0.12)x10(-3). This is the first observation of a charmed meson decaying into a baryon-antibaryon final state.

Production asymmetry of Ds from 600 GeV/c Σ− and π− beam

The production of Ds− relative to Ds+ as a function of xF with 600 GeV/c Σ− beam is measured in the interval 0.15<xF<0.7 by the SELEX (E781) experiment at Fermilab. The integrated charge asymmetries with 600 GeV/c Σ− beam (0.53±0.06) and π− beam (0.06±0.11) are also compared. The results show the Σ− beam fragments play a role in the production of Ds−, as suggested by the leading quark model.

Conformer-specific photoconversion of 25-hydroxytachysterol to 25-hydroxyprevitamin D3: role in the production of vitamin Ds.

The photochemical goal in the production of vitamin Ds (Vit Ds) is to maximize the conversion of the provitamins (Pros) to the previtamins (Pres) while minimizing stoichiometric losses to undesirable over-irradiation products. The last step in the syntheses, the [1,7]-sigmatropic rearrangement of the Pres to the Vits, is thermally induced. The competition between cis-trans photoisomerization and photocyclization of the Pres is known to be highly excitation-wavelength specific. It inspired Havinga's nonequilibration of excited rotamers (NEER) principle and more recent alternative explanations. In contrast, the photochemistry of tachysterol has been reported to be relatively unexceptional with Tachy --> Pre quantum yields in the 0.10-0.13 range, independent of lambdaexc. Examination of the spectrum of the 25-hydroxy derivative of tachysterol (HOTachy) reveals vibronic structure between 295 and 260 nm and a broad structureless shoulder between 330 and 295 nm. These features are consistent with absorption by at least two Tachy conformers. We show that these conformers differ dramatically in their trans-to-cis photoisomerization efficiency. The Tachy --> Pre quantum yield at 313 nm (0.42) in degassed methanol solution is substantially higher than at 254 nm (0.12). On the basis of recent theoretical predictions, it is likely that 313 nm selectively excites the cEc HOTachy conformer which gives photoisomerization much more efficiently than do the other expected conformers (cEt, most abundant, and tEt). Efficient conversion of HOPro D3 to HOPre D3 is accomplished by a two-stage 254/313-nm irradiation sequence. Use of 313 nm in the second step is preferable to previously proposed much longer wavelengths that were hardly absorbed by HOTachy.

Neutrino induced hard exclusive Ds production

Motivated by the possibility to use high intensity neutrino beams for neutrino-nucleon scattering experiments we analyze charged current induced exclusive meson production within the framework of generalized parton distributions. The cross section for hard exclusive D_s production is estimated in this formalism to leading order in QCD. The integrated cross section proves to be sizable. It is shown that the considered process is well suited to provide novel information on the gluon structure of nucleons, which is contained in the generalized gluon parton distribution.

Metabolic engineering of Lactobacillus helveticus CNRZ32 for production of pure L-(+)-lactic acid.

Expression of D-(-)-lactate dehydrogenase (D-LDH) and L-(+)-LDH genes (ldhD and ldhL, respectively) and production of D-(-)- and L-(+)-lactic acid were studied in Lactobacillus helveticus CNRZ32. In order to develop a host for production of pure L-(+)-isomer of lactic acid, two ldhD-negative L. helveticus CNRZ32 strains were constructed using gene replacement. One of the strains was constructed by deleting the promoter region of the ldhD gene, and the other was constructed by replacing the structural gene of ldhD with an additional copy of the structural gene (ldhL) of L-LDH of the same species. The resulting strains were designated GRL86 and GRL89, respectively. In strain GRL89, the second copy of the ldhL structural gene was expressed under the ldhD promoter. The two D-LDH-negative strains produced only L-(+)-lactic acid in an amount equal to the total lactate produced by the wild type. The maximum L-LDH activity was found to be 53 and 93% higher in GRL86 and GRL89, respectively, than in the wild-type strain. Furthermore, process variables for L-(+)-lactic acid production by GRL89 were optimized using statistical experimental design and response surface methodology. The temperature and pH optima were 41 degrees C and pH 5.9. At low pH, when the growth and lactic acid production are uncoupled, strain GRL89 produced approximately 20% more lactic acid than GRL86.

Signal transduction pathways mediating CCK-induced gallbladder muscle contraction.

The signal transduction that mediates CCK-induced contraction of gallbladder muscle was investigated in the cat. Contraction was measured by scanning micrometry in single muscle cells isolated enzymatically with collagenase. Production of D-myo-inositol 1,4, 5-trisphosphate (IP3) and sn-1,2-diacylglycerol (DAG) was quantitated using HPLC and TLC, respectively. Protein kinase C (PKC) activity was determined by measuring the phosphorylation of a specific substrate peptide from myelin basic protein, Ac-MBP-(4-14). CCK-induced contraction was blocked by incubation in strontium medium, pertussis toxin (PTx), and antibodies against Gialpha3 or betagamma-subunits but was not blocked by Ca2+-free medium or by antibodies against Gq/11alpha, Gialpha1-2, or Goalpha. The contraction induced by CCK was inhibited by the phospholipase C (PLC) inhibitor U-73122, anti-PLC-beta3 antibody, and the IP3 receptor antagonist heparin but was not inhibited by the the phospholipase D inhibitor propranolol or antibodies against PLC-beta1 or PLC-beta2. Western blot analysis of gallbladder muscle revealed the presence of PLC-beta2 and PLC-beta3 but not PLC-beta1. CCK caused a 94% increase in IP3 generation and an 86% increase in DAG generation. A low dose of CCK caused PKC translocation, and CCK-induced contraction was blocked by the PKC inhibitor H-7. A high dose of CCK, however, caused no PKC translocation, and its contraction was blocked by the calmodulin antagonist CGS9343B. In conclusion, CCK contracts cat gallbladder muscle by stimulating PTx-sensitive Gi 3 protein coupled with PLC-beta3, producing IP3 and DAG. Low doses activate PKC, whereas high doses activate calmodulin.

Asymmetries between the production of D− and D+ mesons from 500 GeV/c π− nucleon interaction as functions of x and p2

This paper presents measurements of the production of Ds- mesons relative to Ds+ mesons as functions of x_F and square of p_t for a sample of 2445 Ds decays to phi pi. The Ds mesons were produced in Fermilab experiment E791 with 500 GeV/c pi- mesons incident on one platinum and four carbon foil targets. The acceptance-corrected integrated asymmetry in the x_F range -0.1 to 0.5 for Ds+- mesons is 0.032 +- 0.022 +- 0.022, consistent with no net asymmetry. The results, as functions of x_F and square of p_t, are compared to predictions and to the large production asymmetry observed for D+- mesons in the same experiment. These comparisons support the hypothesis that production asymmetries come from the fragmentation process and not from the charm quark production itself.

Effects of temperature, salinity and agitation on byssus thread formation of zebra musselDreissena polymorpha

Byssus thread production ofD. polymorpha under different conditions of temperature, salinity and agitation were studied in the laboratory. The acclimation to salinity and temperature greatly affects the byssus production ofD. polymorpha. Byssus production of mussels was significantly reduced when temperature increased beyond 20°C and decreased below 10°C. Mussels with cut threads (for counting), produced a substantially increased number of threads. However, mussels with uncut byssus threads were comparatively more mobile. Byssus production of mussels did not vary significantly at salinities up to 3‰. Beyond this salinity byssus production was reduced significantly. Mussels increased their byssus production with increasing frequency of agitation.

A measurement ofD meson production inZ 0 hadronic decays

A study of the fragmentation properties of charm and bottom quarks intoD mesons is presented. From 263 700Z0 hadronic decays collected in 1991 with the DELPHI detector at the LEP collider,D0,D+ andD*+ are reconstructed in the modesK−π+,K−π+K+ andD0π+ followed byD0→K−π+, respectively. The fractional decay widths\(\Gamma {{(Z^0 \to {D \mathord{\left/ {\vphantom {D {\bar D}}} \right. \kern-\nulldelimiterspace} {\bar D}}X)} \mathord{\left/ {\vphantom {{(Z^0 \to {D \mathord{\left/ {\vphantom {D {\bar D}}} \right. \kern-\nulldelimiterspace} {\bar D}}X)} {\Gamma _h }}} \right. \kern-\nulldelimiterspace} {\Gamma _h }}\) are determined, and first results are presented for the production ofD mesons from\(c\bar c\) and\(b\bar b\) events separately. The average energy fraction ofD*± in charm quark fragmentation is found to be 〈XE(D*)〉c=0.487±0.015 (stat)±0.005 (sys.). Assuming that the fraction ofDs and charm-baryons produced at LEP is similar to that around 10 GeV, theZ0 partial width into charm quark pairs is determined to beΓc/Γh=0.187±0.031 (stat)±0.023 (sys). The probability for ab quark to fragment into\(\bar B_s \) orb-baryons is inferred to be 0.268±0.094 (stat)±0.100 (sys) from the measured probability that it fragments into a\(\bar B^0 \) orB−.

The study of the BS meson at Delphi

Abstract In the Z 0 hadronic decays a sizeable fraction of BS meson is produced. Various methods used in the study of BS meson properties are described, including the DS -lepton correlation, the study of inclusive DS production and the exclusive reconstruction of BS decays. The results presented are the first evidences of BS production based on 1991 data, the measurement of the BS mass, m (BS ) = 5374 ± 16 ± 2 MeV, and the BS lifetime, τ(BS ) = 1.11±0.27 ± 0.17ps.

Production rate and decay lifetime measurements ofB s 0 mesons at LEP usingD s and? mesons

The study of the properties of inclusive production ofD s mesons and of events in which a ϕ and a muon are present in the same jet provides two independent measurements of the probability,f ws , for a heavy quark to hadronize into a strangeB orD meson. The data sample analysed corresponds to 243,000 hadronicZ 0 decays. The combined value of these measurements isf ws =0.19±0.06±0.08. From the flight distance distributions ofD s and of (ϕ-lepton) secondary vertices, with the lepton emitted at high transverse momentum relative to the jet axis, two values are obtained for theB 0s meson lifetime. Combining these measurements with a previous result based on the study ofD s-μ events, theB 0s meson lifetime is measured to be: 0.96±0.37 ps.

A measurement ofD meson production inZ 0 hadronic decays

A study of the fragmentation properties of charm and bottom quarks intoD mesons is presented. From 263 700Z 0 hadronic decays collected in 1991 with the DELPHI detector at the LEP collider,D 0,D + andD *+ are reconstructed in the modesK − π +,K − π + K + andD 0 π + followed byD 0→K − π +, respectively. The fractional decay widths\(\Gamma {{(Z^0 \to {D \mathord{\left/ {\vphantom {D {\bar D}}} \right. \kern-\nulldelimiterspace} {\bar D}}X)} \mathord{\left/ {\vphantom {{(Z^0 \to {D \mathord{\left/ {\vphantom {D {\bar D}}} \right. \kern-\nulldelimiterspace} {\bar D}}X)} {\Gamma _h }}} \right. \kern-\nulldelimiterspace} {\Gamma _h }}\) are determined, and first results are presented for the production ofD mesons from\(c\bar c\) and\(b\bar b\) events separately. The average energy fraction ofD *± in charm quark fragmentation is found to be 〈X E (D *)〉 c =0.487±0.015 (stat)±0.005 (sys.). Assuming that the fraction ofD s and charm-baryons produced at LEP is similar to that around 10 GeV, theZ 0 partial width into charm quark pairs is determined to beΓ c /Γ h =0.187±0.031 (stat)±0.023 (sys). The probability for ab quark to fragment into\(\bar B_s \) orb-baryons is inferred to be 0.268±0.094 (stat)±0.100 (sys) from the measured probability that it fragments into a\(\bar B^0 \) orB −.

Enhanced production ofd(−)-lactic acid by mutants ofLactobacillus delbrueckii ATCC 9649

Chemical mutagenesis with ethyl methanesulfonate (EMS) was used to develop strains ofLactobacillus delbrueckii (ATCC 9649) that tolerated increased lactic acid concentrations while continuously producing the acid. Three mutants (DP2, DP3 and DP4) were compared with wild-typeL. delbrueckii by standing fermentations with different glucose concentrations. All three mutants produced higher levels of lactic acid than the wild-type. In pH-controlled (pH 6.0) stirred-tank-batch fermentations, mutant DP3 in 12% glucose, 1% yeast extract/mineral salt/oleic acid medium produced lactic acid at a rate that was more than 2-times faster than the wild-type. Mutant DP3 also produced 77 g/l lactic acid compared with 58 g/l for the wild-type. Overall, compated with wild-type, the mutants DP2 and DP3 exhibited faster specific growth rates, shorter lag phases, greater lactic acid yields, tolerated higher lactic acid concentrations, and produced as much as 12% lactic acid in 12% glucose, 3% yeast extract/mineral salt/oleic acid medium which required an additional 9% glucose when the residual glucose concentration decreased to ≤3%. Mutant DP3 was stable for over 1.5 years (stored freeze dried). The strain development procedure was very successful; mutants with enhanced lactic acid-producing capacity were obtained each time the procedure was employed.