Contribution of single diffraction dissociation to highp T production in proton-proton collisions at\sqrt s = 62 GeV at the CERN ISR

The contribution of single diffraction dissociation to highp _T particle production has been determined with the split field magnet detector. For transverse momentap _T >2 GeV/c and production angles θ>10° it is found to be less than 5% for all types of trigger particles. Specifically, a diffractive origin of the large production cross section for highp _T protons can be excluded. The contributions found to highp _T production are found to be in good agreement with extrapolations of the relative particle yields from single diffraction dissociation observed in inelastic minimum bias events.     

High-pT pion production in ππ interactions

Charged pion production in high energy π^-π^- interactions is studied in the p_T region of 1–2 GeV/c. The characteristics of pion production in π^-π^- interactions are compared with those in π^-p and pp interactions. The p_T dependence of pion production in these reactions follows a systematic trend which indicates that high-p_T pion production for ππ interactions as well as for πp and pp interactions proceeds via quark-quark scattering as predicted by QCD.     

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.     

NOX production by impulse sparks in air

An experimental study on the production of NO_X by impulse sparks in air is presented. The emphasis is placed on the dependence of the NO_X yield on the signature of the discharge current waveforms. A voltage and two current impulses were used in the experiments to create a spark and the NO_X production was measured by the method of chemiluminescence. The results show that, for a given current waveform, the NO_X production varies linearly with the peak current and the gap length. In addition, it was found that the NO_X yield increases with the duration of the current for a given peak current.     

Associated production of heavy Higgs boson with top quarks

Associated production of a heavy Higgs boson (m_H > 100 GeV) with top quarks at Juratron energies is studied. It is natural to differentiate between the “light” (2m_t < m_H < 2m_W) and “heavy” (m_H > 2m_W) Higgs search. It is assumed that the mass value of the top quarks is in the interval m_t ≈ 30–80 GeV. m_W is the W-boson mass. If m_H < 2m_W a dangerous background is given by the QCD production of four top quarks. We have calculated the cross sections for both the Higgs production and the background reaction. The disappointing result found is that the background is overwhelmingly large. However the Higgs search in this mass region is not hopeless. The associated production of the Higgs boson with a W-boson may have a clear experimental signature, its background given by the reaction $\text{p}\text{+}\text{p}\text{→}\text{W}\text{+}\text{t}\text{+}\text{t}$ might be suppressed. The difficulty with this mechanism is that the rate is rather low. If m_H > 2m_W the background is different and its contribution is expected to be small. The associated production of a Higgs boson with a pair of top quarks might be a useful method in the Higgs search in this case.     

Inclusive Pomeron-Pomeron interactions at the CERN ISR

Data are presented for the first time on inclusive Pomeron-Pomeron interactions which produce a central systemX (composed mainly of multimeson states) in proton-proton collisions at \(\sqrt s \) at the CERN ISR. The systemX has a Feynman-x distribution which is sharply peaked atx _f=0, is inconsistent with any significant contributions from Reggeon exchange processes, and has an invariant mass dependence in good agreement with the predicted formM _x ^?2 . Kaon production is about 15% of pion production, nearly independent ofM _x, while proton-antiproton production averages about 5% of pion production and increases withM _x. The structure of the central systemX develops into a jetlike shape, asM _x increases, as would be expected from a model of Pomeron fragmentation. The shape of thex _f(π) distribution in the center of mass of theX system (although not proving existence) is consistent with asoft partonic substructure of the Pomeron.     

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.     

Comparison of π±, K± and p,p production in the central rapidity region in hadron-hadron collisions and in e+e− annihilation

We compare the p_T dependence of pion, kaon and proton production cross sections in the central rapidity region in e⁺e⁻ annihilation events and in proton-proton collisions at ISR energies. We find similarities both in the p_T dependence of cross sections and in the particle composition as a function of p_T, in agreement with the hypothesis of a universal mechanism of particle production.     

Consequences of diffractive heavy flavor production

We calculate the lepton spectrum inpp collisions from the production and semileptonic decay ofΛ _c andΛ _b , and find limits on their production cross sections. Total cross sections in excess of 1 mb forΛ _c and 2 1/2μb forΛ _b violate the experimental fact that (μ/π)?10^?4. Abundant production ofΛ _c has led to speculations on the existence of a large intrinsic charm sea inside the proton. We discuss alternative ways of probing such a structure inside the proton: jets opposite highp _T direct photons and central production of ψ.     

On the production of a lepton pair in the collision of ultrarelativistic neutral particle with nonzero magnetic moment with nuclei

Explicit formulas which describe muon pair production in reaction γν→μ⁺μ⁻ν through neutrino magnetic moment are obtained and used to derive in the leading approximation cross section of muon pair production in νN-scattering due to neutrino magnetic moment. This cross section appears to be proportional to log⁴E_ν. Comparison with experimental data on tridents production provides an upper bound μ_νμ<4×10⁻⁸μ_B, which is approximately two orders of magnitude weaker than that from ν_μe elastic scattering data.     

Production of prompt leptons in a cluster model

Prompt lepton production in hadron collisions is explained in a cluster production model, by assuming that the clusters have a small branching ratio for decay into leptons. The production of low mass and small momentum clusters, normalized to reproduce pionization, can explain the observed large increases of e/π ratio for decreasing p_bdT at large angles and the decreasing values of ω/π with increasing x_lab near the forward direction. The present model predicts a large increase of the e/ω ratio near the forward direction as x_lab increases.     

Systematic study of impact parameter dependent K-vacancy probabilities in near symmetric gas- and solid-target collision systems

K-vacancy production probabilitiesP _K (b) were measured with gas and solid targets byK-x-ray particle coincidences (impact parameterb is determined by the particle detection angle) in the region of light (Z _P ?Z _T ?10) up to intermediate heavy (Z _P ?Z _T ?36) collision systems. The measuredP _K (b) reveal a very strong difference in shape between solid and gas targets independent ofZ. Only theP _K (b) measured with gas targets and those measured with solid targets at very small impact parameters show reasonable good agreement with the 2pπ _x-2pσ rotational coupling model. At largeb theP _K (b) from solid targets are strongly influenced by a multiple collision effect, where projectileL-vacancies seem to be produced in collisions beforeK-vacancy production. However, this effect cannot be understood just by a two collision process whereL-vacancy production and 2pπ _x-2pσ rotational coupling occurs in consecutive collisions.     

Flavor correlations in B s -and B c -meson production at hadron colliders

We present a comparative analysis of three different theoretical approaches to the production of B _s and B _c mesons in high-energy hadron collisions. Our attention focuses on the azimuthal and pseudorapidity correlations between B _s or B _c mesons and accompanying strange or charmed particles. The corresponding kinematical distributions are found to exhibit a high sensitivity to details of the production mechanism and can therefore serve as indicators of interaction dynamics.     

Inclusivef 2 (1270) meson production in νp and\bar vp charged current interactions

Using data obtained with the bubble chamber BEBC at CERN, the inclusivef ₂ (1270) meson production invp and \(\bar vp\) charged current reactions is studied. It is found thatf ₂ production occurs mainly in events with a hadronic invariant massW?7 GeV. In these events, the averagef ₂ multiplicity is about half the average ρ^O multiplicity, and thex _F andp _T ² distributions of thef ₂ agree in shape with those of the ρ^O. The predictions of a semi-empirical model (Wells model) are in accord with the measured multiplicities atW>7 GeV, whereas at lowerW the model predicts too largef ₂ multiplicities.     

Inclusive cross section and single transverse-spin asymmetry of very forward neutron production at PHENIX

The cross section and x _F dependence of A _N of very forward neutron production in polarized p + p collisions at √s = 200 GeV were measured in the PHENIX experiment at RHIC. The measured cross sections were consistent with the x _F scaling claimed by the ISR experiment. Significant negative A _N was observed in the forward region, and no significant backward A _N was observed. We also measured √s and p _T dependence of A _N of very forward neutron production at √s from 62.4 to 500 GeV.     

Hadronic production ofS- andP-wave states of\bar b-quarkonium-quarkonium

In the leadingO(α _s ⁴ ) order of the perturbative QCD, the hadronic production cross-sections ofS- andP-wave states ofB _c meson are calculated. The results for theS-wave levels are compared with the values given in other papers as well as in the model of thebquark fragmentation intoB _c . In the given order, the cross-sections of the hadronic production of theP-wave states are calculated for the first time. Their contribution into theB _c meson production is less than 10%. There is a strong difference between the predictions of the fragmentation model and the exact perturbative calculations. These differences are discussed in details for the differential distributions over various kinematical quantities.     

Observation of possible production and decay of short-living heavy neutral particles in the SKAT neutrino experiment

In the SKAT bubble chamber neutrino experiment production of a short-living neutral particle with mass (1.4?m?2.5) GeV/c² and lifetime τ≈6×10^?12 s has been detected. The event may be interpreted as production and decay of the heavy lepton M⁰→μ^?+e⁺+ν_e with mass (1.4?m_M⁰?2.1) GeV/c². It might also be the production of a charmed particle D⁰→e⁺+τ^?+ν_e (D⁰→e⁺+π^?+ν_e) with mass 1.4?m_D⁰?2.5) GeV/c² in a non-diagonal neutral current. The probability to interpret the event as other possible processes is very low.     

The study of the proton-proton collisions at the beam momentum 1581 MeV/c

The new data on the elastic pp and single-pion production reaction pp → pnπ ⁺ taken at the incident proton momentum 1581 MeV/c are presented. To extract contributions of the leading partial waves the single-pion production data are analyzed in the framework of the event-by-event maximum-likelihood method together with pp → ppπ ⁺ data measured earlier and the pp → pnπ ⁺ data taken at 1628 MeV/c. The analysis shows that at 1581 MeV/c the largest contributions stem from the ³ P ₂, ³ P ₁, ³ P ₀ and ³ F ₂ initial partial waves. From these partial waves we also deduce contributions for the production of the Δ(1232) and N(1440) states.     

K-vacancy production by 3.6-, 4.75-, and 5.9-MeV/amu238U Ions

Projectile (Z ₁) and target (Z ₂)K-vacancy production cross sections induced by 3.6-, 4.75-, and 5.9-MeV/amu²³⁸U ions in selected targets between C and U are reported. The cross sections are discussed within the context of the molecular model of inner-shell vacancy production in heavy-ion-atom collisions. The measured 1sσ and 2pσ excitation cross sections are compared with semiempirical formulas, and with the perturbed-stationary-states calculations of Betz et al. The dependence of these cross sections onZ _u =Z₁+Z ₂ agrees well with the Betz calculations. However, the measured cross sections are factors of 2 to 4 (1sσ) and 4 to 5 (2pσ) larger than the theoretical values.     

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.