Entropy Production Analysis of a Vertical Mixed-Flow Pump Device with Different Guide Vane Meridians

With the aim of investigating the influence of guide vane meridians on the external characteristics and internal flow field of the mixed-flow pump device, this research constructed seven guide vane meridians and applied computational fluid dynamic (CFD) and entropy production theory to investigate the spread of hydraulic loss in a mixed-flow pump. As observed, when the guide vane outlet diameter D_gvo decreased from 350 mm to 275 mm, the head and efficiency increased by 2.78% and 3.05% at 0.7 Q_des, respectively. At 1.3 Q_des, when D_gvo increased from 350 mm to 425 mm, the head and efficiency increased by 4.49% and 3.71%, respectively. At 0.7 Q_des and 1.0 Q_des, the entropy production of the guide vane increased with the increase of D_gvo due to flow separation. When D_gvo < 350 mm, at 1.0 Q_des and 1.3 Q_des, entropy production of the outlet channel increased as D_gvo decreased owing to the excessive flow rate, but at 0.7 Q_des, entropy production did not change much. When D_gvo > 350 mm, at 0.7 Q_des and 1.0 Q_des, due to the expansion of the channel section, the flow separation intensified, which resulted in an increase of the entropy production, but the entropy production decreased slightly at 1.3 Q_des. These results provide guidance for improving the efficiency of pumping stations.     

χ<Subscript><Emphasis Type="Italic">cJ</Emphasis></Subscript> polarization in polarized proton–proton collisions at RHIC

We study inclusive χ _cJ production with definite polarizations in polarized proton-proton collisions at \(\sqrt s \) = 200 and 500 GeV at RHIC by using non-relativistic QCD (NRQCD) color-octet mechanism. We present results of rapidity distribution of χ _c0, χ _c1 and χ _c2 production with specific polarizations in polarized p–p collisions at RHIC within the PHENIX detector acceptance range. We also present the corresponding results for the spin asymmetries.     

Measurement of A LL and cross section of high p T charged π meson production for constraining ΔG at PHENIX

PHENIX at RHIC measured invariant differential cross section and double helicity asymmetry A _LL of high p _T charged pions production in polarized p + p collision at √s = 200 GeV. Interpretations of preliminary results regarding constraining gluon helicity distribution are discussed.     

A study of A2 and g resonance production in π−p→K−K0p

We present the results and the analysis of a high-statistics experiment to study A₂ and g production in the reaction π^?p→K^?K_S⁰p at 10 GeV/c. In each resonance region we perform a moment analysis of the data, and from the moments we determine the production amplitudes as a function of t. We find A₂ production proceeds dominantly by natural-parity (pomeron and f) exchange. We compare A₂ and diffractive K¹ (1420) production. We find g production proceeds by π and ω exchanges; we determine the $\text{g}\text{→}\text{K}\text{K}$ branching ratio.     

A partial wave analysis of the (Kππ) system in the reaction π− p→(K +π−π0)Λ at 3.95 GeV/c

Results from a partial wave analysis of theKππ system produced in the hypercharge exchange reaction π^? p→(K ⁺π^?π⁰)Λ at 3.95 GeV/c are presented. SignificantQ ₁ production is observed but no evidence is found forQ ₂ production thus confirming the results obtained in a previous decay Dalitz plot analysis of the same reaction. The relative phase behaviour of the 1⁺(K?) partial waves obtained with the present analysis provides additional confirmation of the resonance interpretation of theQ ₁ enhancement. Information is also obtained about its production properties and the role played by the Λ polarization in the hypercharge exchange reaction. This is compared with the results obtained in the reactionK ^? p→(π⁺π^?π⁰)Λ at 4 GeV/c.     

Charged particle production at the CERN ISR as a function of transverse momentum

Experimental results are presented on the production of charged particles in inclusive reactions at ISR energies. The data have been taken as function of transverse momentum p_t at the fixed x-values of 0.08, 0.16 and 0.32. The behaviour of the p_t-distributions for the different particles is discussed.     

The total cross section for the production of heavy quarks in hadronic collisions

We present the results of a full calculation of the QCD O(α_S³) radiative corrections to the total cross section for the production of a heavy quark pair. We find large contributions for parton subenergies near threshold and well above threshold. The implications for the production of top and bottom quarks at collider energies are discussed.     

Search for neutral heavy leptons produced in Z decays

Weak isosinglet Neutral Heavy Leptons (v _m) have been searched for using data collected by the DELPHI detector corresponding to 3.3 × 10⁶ hadronic Z⁰ decays at LEP1. Four separate searches have been performed, for short-lived v _m production giving monojet or acollinear jet topologies, and for long-lived v _m giving detectable secondary vertices or calorimeter clusters. No indication of the existence of these particles has been found, leading to an upper limit for the branching ratio BR(Z⁰ → v _m ?) of about 1.3 × 10^?6 at 95% confidence level for v _m masses between 3.5 and 50 GeV/c². Outside this range the limit weakens rapidly with the v _m mass. The results are also interpreted in terms of limits for the single production of excited neutrinos.     

Search for heavy quasistable leptons

Negative results of a search for heavy quasistable charged leptons at the IHEP accelerator are reported. For the selection of heavy leptons a system of scintillation and gas ?erenkov counters was used. The upper limit estimations of the differential cross sections for heavy lepton production in pN collisions at E_p = 70 GeV are, for example, d²σ/dpω (p = 30 GeV/c, θ = 2 mrad, 1 ? M_λ ? 4.8 GeV) = 4.10^?38 cm²/sr · GeV. The results of the present work, together with the data on muon pair production in nucleon-nucleon interactions, show that there are no heavy charged leptons with masses from 0.55 GeV (τ_λ > 7 · 10^?10 sec) up to 4.5 GeV (τ_λ > 3 · 10^?8 sec).     

Investigation of neutral-kaon production in pC,pSi and pPb Collisions at 70 GeV/c

The results obtained by measuring the inclusive distributions of the Feynman variable x _F and the transversemomentum for the production of K _S ⁰ mesons in proton-nucleus interactions at 70 GeV/c for three targets (C, Si, and Pb) are presented. The mass-number (A) dependence of the cross section for K _S ⁰ -meson production is studied. The measured value of the exponent α in the formula σ ～ A ^α agrees within the errors with its counterpart at higher energies. With the aid of the A dependence, the measured yield of K _S ⁰ mesons at x _F = 0 is compared with the yield of K ⁺ and K ^? mesons in the proton-proton reaction at 70 GeV/c. The inclusive spectra of longitudinal and transverse variables for K _S ⁰ -meson production are contrasted against the predictions of the FRITIOF and UrQMD models.     

Constraints on large-extra-dimensions model through 125 GeV Higgs pair production at the LHC

Based on the analysis of 5?fb^?1 of data at the LHC, the ATLAS and CMS collaborations have presented evidence for a Higgs boson with a mass in the 125 GeV range. We consider the 125 GeV neutral Higgs pair production process in the context of large-extra-dimensions (LED) model including the Kaluza?CKlein (KK) excited gravitons at the LHC. We consider the standard model (SM) Higgs pair production in gluon?Cgluon fusion channel and pure LED effects through graviton exchange as well as their interferences. It is shown that such interferences should be included; the LED model raises the transverse momentum (P _t ) and invariant mass (M _HH ) distributions at high scales of P _t and M _HH of the Higgs pair production. By using the Higgs pair production we could set the discovery limit on the cutoff scale M _S up to 6 TeV for ??=2 and 4.5 TeV for ??=6.     

φ production in In–In collisions at 158 A GeV

The NA60 experiment has measured muon pair production in In–In collisions at 158 AGeV at the CERN SPS. This paper presents a high statistics measurement of φ→μ μ meson production. Differential spectra, yields, mass and width are measured as a function of centrality and compared to previous measurements in other colliding systems at the same energy. The width of the rapidity distribution is found to be constant as a function of centrality, compatible with previous results. The decay muon polar angle distribution is measured in several reference frames. No evidence of polarization is found as a function of transverse momentum and centrality. The analysis of the p _T spectra shows that the φ has a small radial flow, implying a weak coupling to the medium. The T _eff parameter measured in In–In collisions suggests that the high value observed in Pb–Pb in the kaon channel is difficult to reconcile with radial flow alone. The absolute yield is compared to results in Pb–Pb collisions: though significantly smaller than measured by NA50 in the muon channel, it is found to exceed the NA49 and CERES data in the kaon channel at any centrality. The mass and width are found to be compatible with the PDG values at any centrality and at any p _T : no evidence for in-medium modifications is observed.     

Neutrino production of M+ and E+ heavy leptons (I)

A theoretical study is made of M⁺ and E⁺ heavy lepton production in inclusive neutrino reactions. The production cross sections on protons are found to be enhanced over those for isoscalar targets and can in principle exceed the cross sections for the ordinary v_μ+p→μ^?+X process at high energies. New estimates are given for the decay branching ratios taking into account the SPEAR data on electron positron annihilation. Monte Carlo techniques are employed to calculate q² ? v spectra and y distributions for both the production process where v_μ→M⁺ and the effective process where v_μ→μ⁺. The normalized results are rather insensitive to the set of structure functions used.     

Analysis of Energy Loss Characteristics of Vertical Axial Flow Pump Based on Entropy Production Method under Partial Conditions

The energy loss of the vertical axial flow pump device increases due to the unstable internal flow, which reduces the efficiency of the pump device and increases its energy consumption of the pump device. The research results of the flow loss characteristics of the total internal conduit are still unclear. Therefore, to show the internal energy loss mechanism of the axial flow pump, this paper used the entropy production method to calculate the energy loss of the total conduit of the pump device to clarify the internal energy loss mechanism of the pump device. The results show that the energy loss of the impeller is the largest under various flow conditions, accounting for more than 40% of the total energy loss of the pump device. The variation trend of the volume average entropy production and the energy loss is similar under various flow coefficients (K_Q). The volume average entropy production rate (EPR) and the energy loss decrease first and then increase with the increase of flow, the minimum volume average entropy production is 378,000 W/m³ at K_Q = 0.52, and the area average EPR of the impeller increases gradually with the increase of flow. Under various flow coefficient K_Q, the energy loss of campaniform inlet conduit is the smallest, accounting for less than 1% of the total energy loss. Its maximum value is 63.58 W. The energy loss of the guide vane and elbow increases with the increase of flow coefficient K_Q, and the maximum ratio of energy loss to the total energy loss of the pump device is 29% and 21%, respectively, at small flow condition K_Q = 0.38. The energy loss of straight outlet conduit reduces first and then increases with the increase of flow coefficient K_Q. When flow coefficient K_Q = 0.62, it accounts for 27% of the total energy loss of the pump device, but its area average entropy production rate (EPR) and volume average entropy production rate (EPR) are small. The main entropy production loss in the pump device is dominated by entropy production by turbulent dissipation (EPTD), and the proportion of entropy production by direct dissipation (EPDD) is the smallest.     

High transverse momentum identified particle spectra in 200 GeV collisions from STAR

Significant baryon over meson enhancement was measured at RHIC in the intermediate transverse momentum range of p _T =2?4 GeV/c (“baryon-meson puzzle”). With STAR detector we were able to extend particle identification towards higher transverse momentum offering further insights into the particle production mechanisms at intermediate to high p _T . In this paper we present results on charged pion, proton and anti-proton spectra and ratios at intermediate to high p _T exploiting the relativistic rise of the specific ionization energy loss measured in the STAR Time Projection Chamber. These measurements provide valuable information about the production mechanisms of particles at intermediate p _T in relativistic heavy ion collisions, e.g. coalescence/recombination versus jet fragmentation.     

High pressure ignition delay times of H2/CO mixture in carbon dioxide and argon diluent

Ignition Delay Time (IDT) plays a significant role in combustion process of advanced power cycles such as direct-fired supercritical carbon dioxide (sCO₂) cycle. In this cycle, fuel and oxidizer are heavily diluted with carbon dioxide (CO₂) and autoignite at a combustor inlet pressure range of 10–30 MPa and a temperature range of 900–1500 K. A fuel candidate for sCO₂ power cycle applications is syngas (H₂/CO mixture); however, its ignition properties at these conditions are not studied. Moreover, the existing chemical kinetics models have not been evaluated for H₂/CO mixtures applications relevant to elevated pressure conditions and under large dilution levels of CO₂. Therefore, two tasks are performed in this study. First, IDTs of a H₂/CO=95:5 mixture at stoichiometric and rich (Φ=2) conditions are measured in a high-pressure shock tube under 95.5% CO₂ dilution level and at 10 MPa and 20 MPa for a temperature range of 1161–1365 K. For the experimental conditions considered in this work, Aramco 2.0, FFCM-1, HP-Mech and USC Mech II kinetic models are capable of capturing IDT data. Second, similar experiments are conducted by replacing the CO₂ dilute gas with Argon (Ar) to understand the chemical effect of CO₂ on IDT globally. Sensitivity analysis results reveal that for both diluents, reaction H + O₂(+M)=HO₂(+M) is the most important reaction in controlling ignition. Further, a rate of production analysis shows that CO₂ has a competing effect on OH radical production. On one hand, CO₂ accelerates the consumption of H radicals through H + O₂+CO₂→HO₂+CO₂ therefore hindering HO₂+HOH+OH reaction for OH production. On the other hand, CO₂ is shown to enhance OH production through H₂O₂+M=OH+OH+M. These kinetic effects from CO₂ cancel out, therefore CO₂ does not significantly alter the IDT globally when compared to the Ar bath case. This is confirmed by both experimental results and simulation.     

ϒ production at large transverse momentum as a probe of axigluons

Large-p_T production of J/Ψ and ϒ particles is suggested as a sensitive probe of axigluons of mass less than 40 GeV at the CERN collider and 80 GeV at the Tevatron. It is shown that existing CERN collider data on large-p_T ϒ production exclude axigluon masses less than around 20 GeV. At the projected SSC, ϒ and vector toponium production at large p_T through axigluon exchange by far outweighs the QCD contribution over a vast range of axigluon and toponium masses.     

K − and\bar p Production in Au + Pb Collisions at 11.5 A GeV/cProduction in Au + Pb Collisions at 11.5 A GeV/c

I will present the first results from the E864 collaboration on the production of negative kaons and antiprotons in 10% central 11.5 A GeV/c Au+Pb nucleus collisions at the Brookhaven AGS. E864 is a high rate, open geometry spectrometer, capable of measuring particle production in a range of rapidities and transverse momenta at a single setting of the spectrometer magnets. The results are derived from the analysis of over 20 million central interactions collected in the Fall 1994 run. I will report onK ^? production in a rapidity range from 1.9<y<2.2 (y _cm=1.6) and 25<pT<150 MeV/c, and $\bar p$ production from 1.2<y<2.2 and 50<pT<400 MeV/c. A comparison with previously published results from E878 is presented and the implications for $\bar \Lambda $ production are discussed.     

Inclusive proton and antiproton production in π± hydrogen and π± nucleus interactions at 30 GeV/c

Data on fast protons and antiprotons produced byπ ^± incident on hydrogen and nuclear targets at 30 GeV/c are presented. The results covering the kinematic range 0.32 F <0.54 andp _T >0.2 GeV/c, complete our previous paper. We give results on inclusive cross-sections as a function ofx _F , ofp _T ² and on cross-section ratios. A search for effects of nuclear matter on the production of protons and antiprotons has yielded no major effects beyond final state absorption.     

Single-spin asymmetry of inclusive neutral-pion production in pp ↑ interactions at 70 GeV in the region −0.4 < x F < −0.1

For the kinematical region specified by the inequalities ?0.4 < x _F < ?0.1 and 0.9 < p _T < 2.5 GeV/c, the results are presented that were obtained by experimentally determining the single-spin asymmetry of inclusive neutral-pion production in the reaction p + p _↑ → π ⁰ + X at 70 GeV. According to these results, the asymmetry is close to zero in the region ?0.2 < x _F < ?0.1 and grows in magnitude with decreasing x _F, amounting to (?10.6 ± 3.2)% for ?0.4 <x _F < ?0.2.