Spectroscopy of 7Li in stopped pion absorption reactions

The structure of excited levels in the ⁷Li isotope is studied via inclusive and correlation measurements in the stopped π^? meson absorption reactions ¹⁰B(π^?, t)X and ¹²C(π^?, dt)X, respectively. The experiment is conducted using a low-energy pion beam at the LAMPF meson factory. Analysis of the missing mass spectra reveals ⁷Li states with the resonance parameters (E _x , Γ) (4.7, 0.1), (6.6, 0.9), (7.3, 0.1), (9.1, 2.8), and (9.6, 0.4) MeV. A highly excited state with E _x ≈ 11.2 MeV (i.e., an isobar analog of ⁷He) is observed in the ¹⁰B(π^?,t)X reaction. An excited state with E _x = 10.3 ± 0.1 MeV and γ = 1.8 ± 0.4 Mev is observed for the first time in the ¹²C(π^?,dt)X reaction.     

Prediction of Re ɛ fromK 13 decays in an extended cabibbo model

With the help of an extended Cabibbo model for the weak hadronic vector current which includes the 10 and ¯10 representations to account for possibleΔS=-ΔQ transitions, a prediction is made for the quantity (1-¦x¦²)/¦1?x¦² wherex=A(K⁰→π^üe^?¯v)/A(¯K⁰→π^üe^?¯v) using the experimental branching ratio Γ(K^?→ π⁰e^?¯v/Γ(K _L ⁰ →π^üe^?¯v). From the known charge asymmetry in the decay of the long lived kaon one then obtains Re?.     

Study of longitudinal distributions in the fragmentation regions,using the quark-parton model,in K−p interactions at 70 GeV/c

The study of π^±, π⁰, K⁰ and Λ production in the fragmentation regions (|x|0.2) of K^?p interactions at 70 GeV/c shows that the x-dependence of each invariant cross section is well described by the power law (1?|x|)ⁿ suggested by the dimensional counting rule. Furthermore, pion production is found, both in K^? and proton fragmentation regions, to be very similar to their production in $\text{ν(}\text{ν}\text{)}\text{p}$ interactions as expected from quark-parton models. The quark and diquark fragmentation functions D_u^π, D_uu^π and D_ud^π are extracted from our data.     

Phase-shift analysis of π N → K Σ

We have performed an energy-independent phase-shift analysis of πN → KΣ by analyzing differential cross-section and polarization data for the reactions π⁺p → K⁺∑⁺ and

at fifteen energies from threshold to 2137 MeV invariant mass. The single-energy solutions were linked by shortest-path methods with and without constraints implied by the Odorico zeros for the reaction π^?p → K⁺Σ^?. Similar to π^?p → KΛ it has been found that both isostates are dominated below 1900 MeV by resonances in the spin $\text{1}\text{2}$ waves. The F₃₇ resonance couples to KΣ with √x_πNx_KΣ= 0.04.     

Evidence for Λc+ in inclusive pp → (Λ0π+π+π−) + X and pp → (K−π+p) + X at √s = 53 and 62 GeV

A search for the charmed baryon, Λ_c⁺, has been carried out in inclusively, measured Λ⁰π^±π⁺π^? and K^?π^±p final states with longitudinal x > 0.75 in an experiment at the CERN intersecting storage rings. An effect with invariant mass near 2.3 GeV is observed in Λ⁰π⁺π⁺π^? with cross section times branching ratio Bσ = (2.8±1.0) μb; similar effect is observed in K^?π⁺p with Bσ = (2.3 ± 0.3) μb. The effect is seen only in the positive charge state, in agreement with an interpretation as Λ_c⁺. However, it is pointed out that in the same experiment, the non-charmed hyperon state Σ(1385)⁺ also has a cross section much larger than its corresponding negative charge state Σ(1385)^?.     

Investigating highly excited states of the 8Li isotope

Highly excited states of the ⁸Li isotope are sought in absorption reactions of π^? mesons stopped by ^10,11B isotopes. The ground and three excited states of the ⁸Li isotope are observed in inclusive measurements of reactions ¹⁰B(π^?, d)X and ¹¹B(π^?, t)X. The states with excitation energies E _x ≈ 8.7 and 10.1 MeV are observed for the first time in correlation measurements of reactions ¹⁰B(π^?, dt)X and ¹¹B(π^?, tt)X.     

Inclusive particle spectra in p(π+)n interactions at 195 GeV/c

We present results on single-particle inclusive distributions in p(π⁺)n reactions from a Fermilab experiment using the hybrid 30″ bubble chamber and PWC facility. Distributions in rapidity, y, Feynman x and p²_T for π⁺ and π^? are presented and compared with other experiments. The effects of different targets and projectiles (neutrons, protons and pions) on the distributions are demonstrated and discussed in terms of projectile and target fragmentation. The average transverse momentum 〈P_T〉 is studied as a function of x, y and multiplicity.     

Strange particles production and absorption in nuclei at high energies

The absorption of the secondary hadrons in nuclear matter is studied as a function of their flavour dependent inelastic cross section on nucleons. In particular the ratiosK ⁺/π⁺ andK ^?/π^? of particles produced in the proton-nucleus high energy interactions are examined and described in the very simple phenomenological model. The enhanced production ofK ⁺ mesons is explained by their relatively small interaction. The presence of the initial particle absorption is clearly demonstrated forx _F>0.5.     

Single-spin asymmetry of inclusive π 0-meson production in 40-GeV pion interactions with a polarized target in the target-fragmentation region

Data on the single-spin asymmetry (A _N) of inclusive π ⁰ production in 40-GeV pion interactions with a polarized target, π^? + _↑→π⁰+X, are presented for the target-fragmentation region. The result is A _N=(?13.8±3.8)% for ?0.8<x _Fp _T<2 GeV/c and is compatible with zero for ?0.4<x _Fp _T<1.5 GeV/c. At a π ⁰ momentum of about 1.7 GeV/c in the c.m. frame, the asymmetry becomes nonzero both in the central and in the target-fragmentation region. The behavior of the asymmetry is similar to that observed in the beam-fragmentation region of the E-704 (FNAL, 200 GeV) and STAR (BNL, 20 TeV) experiments, which employed a polarized proton beam.     

Structure of28Si from the spectroscopy of high-spin states

A search for high-spin states in²⁸Si has been performed byn?y coincidence measurements in the²⁵Mg(α,nγy) reaction atE _α=14 and 15.5 MeV. Spin-parity assignments of the observed levels were obtained fromn?γ angular correlation and lifetime measurements atE _α=14.5 MeV. Theγ-decay of the 9,164 keV level was investigated separately with the²⁷Al(p, γ) reaction at theE _p=2,160 and 2,312 keV resonances. Rotational bands withK ^π=3^? (comprising levels atE _x=6,879, 8,413, 10,188 and 12,204 keV),K ^π =5^? (comprising levels atE _x=9,702, 11,577 and 13,741 keV) andK ^π=0⁺ (comprising levels atE _x=6,691, 7,381, 9,164 and 11,509 keV) were observed. The finding of the latter band supports the idea of coexisting oblate and prolate shapes in²⁸Si. A level at 14,643 keV excitation energy has the properties of theI ^π=8⁺ member of the ground state band. There are additional positive-parity high-spin states which do not fit into rotational bands. All types of positive-parity states are well accounted for by shell model calculations.     

Nuclear structure of 18F: (IV). Negative-parity states

Studies via the ¹⁶O(³He, pγ)¹⁸F, ¹⁴N(α,γ)¹⁸F and ¹⁷O(p, γ)¹⁸F reactions have resulted in new J^π assignments for 11 states or negative parity: E_x(keV) (J^π) = 3791(3^?), 4226(2^(?)), 4398(4^?), 4860(1^(?)), 5502(3^(?)), 5785(2^?), 6097(4^?), 6108(1^(?), 2^(?), 3^(?)), 6241(3^?, T = 1), 6643(2^?, T = 1) and 6878(3^(t-), 4^?). The 6241 keV state is probably isospin mixed. New information for 5 states of positive parity has also been obtained: E_x(keV) (J^π) = 3838(2⁺), 4115(3⁺), 4652(4⁺, T = 1), 4753((0⁺), T = 1) and 4964(2⁺, T = 1). Mean lives, branching and mixing ratios are reported for all states. The results for the negative-parity states are discussed in the framework of the various models available. The states at E_x = 1080(0^?), 2100(2^?) and 4398(4^?) keV are interpreted as the first three members of a K^π = 0^? rotational band.     

Two-prong events in π− p interactions at 4.45 GeV/c

(π^?p → π^?p)_el, π^?p → π^?π⁺n and π^?p → π^?π^op reactions at p_π? = 4.45 GeV/c were studied in a 50 cm hydrogen bubble chamber. Cross sections σ_tot and dσ/dt were measured for these reactions and also for the ?^o, f^o and ?^? resonances. The elastic π^?π⁺ and π^?π^o scattering cross sections were calculated by the Chew-Low extrapolation method and with the pseudoperipheric approximation.     

Coherent production of theK −π+π− system inK −d interactions at 4.5 GeV/c

After summarizing the properties of the socalled Dalitz Array (DA), which is a genuine characteristics of a resonance, we determine those of the well known ε, γ, andA ₂ resonances produced in theK ^? p→π⁺π^?π⁰ Λ final state at 4.2 Ge V/c. A tentative measurement of the DA of theA ₁ meson produced backwards in the reactionK ^? p→π⁺π⁺π^?Σ^? is also presented. The data for this analysis come from the high statistics (130 events/μb) experiment performed by the ACNO Collaboration.     

Multipion production below 1.1 GeV by e+e− annihilation

The production of multipion events by e⁺e^? annihilation has been measured at centre of mass energies 915,990 and 1076 MeV. Both channels e⁺e^?→π⁺π^?π^o and e⁺e^?→π⁺π^?π⁺π^? have been analysed. An energy threshold effect analysed. An energy threshold effect around 919 MeV (m_ω + m_π^o) has been evidenced for the π⁺π^?π^oπ^o channel and the cross section is consistent with the quasi two-body process e⁺e^?→ωπ^o. The cross section for π⁺π^?π⁺π^? is lower by an order of magnitude and increases with the energy.     

Evidence forf 2 (1720) production in the reaction pomeron-pomeron→π+π−π+π−

Data are presented on pomeron-pomeron interactions which produce a central π⁺π^?π⁺π^? system in proton-proton collisions at √s=62 GeV at the CERN Intersecting Storage Rings. A spin-parity analysis of the π⁺π^?π⁺π^? system shows evidence for the production of the statef ₂ (1720) with decay to ρ⁰π⁺π^?. Since pomeron-pomeron interactions are expected to favor the production of gluonic bound states, observation of thef ₂ (1720) supports earlier interpretations of it as a glueball. In addition, enhancements near threshold give indication of the statef ₂ (1270) decaying to ρ⁰ρ⁰ and the statef ₀ (1400) decaying to ρ⁰π⁺π^?.     

Production properties ofD 0,D +,D *+ andD s + in 230 GeV/cπ − andK −-Cu interactions

We have studied the hadronic production of charmed mesons in the NA 32 experiment at CERN. A special trigger together with a high resolution vertex detector consisting of charge coupled devices and silicon microstrip detectors allowed the selection of very clean samples of charmed mesons. We have collected 852 fully reconstructed decays: 60D _s ⁺ →K ⁺ K ^?π⁺, 543D°→K ^?π⁺ andK ^?π⁺π^?π⁺ as well as 249D ⁺→K ^?π⁺π⁺ (or charge conjugate). 147 mesons out of our \({{D^0 } \mathord{\left/ {\vphantom {{D^0 } {\bar D^0 }}} \right. \kern-0em} {\bar D^0 }}\) sample were produced via chargedD ^* state. For all charmed mesons we determine the total production cross-section and study thex _F andp _t ² distributions.     

An extended quark recombination model with valence quark annihilation compared to inclusive π+/π− ratios

Valence quark annihilation with subsequent recombination is considered as the dominant nonscaling process contributing to lowp _⊥ pion production in the proton fragmentation region at medium energies. With the aid of a Kuti-Weisskopf model for quark distribution functions the inclusive ratios π⁺/π^? have been calculated and compared to data forHp→π^± +anything withH=π^±,K ^?, \(\bar p\) . Each of these beam particles carries valence antiquarks. The dependence of the ratios on the Feynman variablex and their energy dependence is well reproduced.     

Charged hadron multiplicities and inclusive π− distributions in inelastic ep scattering

Electroproduction of hadrons is studied in the kinematic region W < 2.8 GeV and 0.3 < Q² < 1.4 GeV² using the DESY streamer chamber. Prong cross sections, charged-particle multiplicities and inclusive π^? distributions are presented. The average charged multiplicity is found to be independent of Q² in the Q² range studied here; however it is lower than in photoproduction. The fraction of forward π^? is found to be significantly less in electroproduction than in photoproduction. The 〈p_⊥²〉 for inclusive π^? is, for all x values, similar to that found in photoproduction.     

Inclusive π0 and η production in the all neutral mode from 100 GeV/cπ−p collisions

Results are givenfor π⁰ and η production in 100 GeV/cπ^?p collisions, summed over all final states with no charged particles present (the all neutral final states). The data are fitted for x?0.6 to a modification of triple Regge theory suggested by the multiperipheral model. We find good agreement between the values of the ? and A₂ trajectories determined in the all neutral process, the full inclusive mode, π^?p → (π⁰, η)X, and the exclusive reactions, π^?p → (π⁰, η)n. The ? exchange residue function shows evidence for a dip at t ≈ ?0.5 (GeV/c)² (the ? wrong signature nonsense zero), whereas the η data are quite smooth in this region. These successful predictions for both the trajectory and residue function are striking evidence for the validity of triple Regge theory.