Covariant partition temperature model ande + e − annihilation

The rapidity distributions of inclusive \(e^ + e^ - \to h\bar h + \cdot \cdot \cdot\) of PEP and DESY experiments are analyzed in terms of the covariant partition temperatureT _p model. The estimates ofT _p ^* in the fireball system are comparable to the conventional temperature, the energy dependence follows approximately Stefan's law, the radius of the specific volume ralative to the energy density being ～1.18 fm. In the c.m.s. of collision, \(T_p = AW^a (W = \sqrt s in GeV)\) witha=0.60±0.05 andA=0.256±0.006, it is found \(T_p \cong {W \mathord{\left/ {\vphantom {W {\tfrac{3}{2}\left\langle {n_ \pm } \right\rangle }}} \right. \kern-0em} {\tfrac{3}{2}\left\langle {n_ \pm } \right\rangle }}\) . These properties hold also for \(\bar pp\) collision, but not forpp→π^?+...     

Joint production of ϕ mesons andπ ±,π 0,p,\bar p,K s 0 andK ± in hadronic interactions

The joint production of ? mesons andπ ^±,π ⁰,p, \(\bar p\) ,K _s ⁰ andK ^± is investigated using a sample of 600,000 inclusive ? meson events obtained in hadron Be interactions with incidentπ ^±,p, \(\bar p\) andK ^± beams. Evidence is presented for the joint production of ? mesons and strange particles produced with non-strange incident beams. With incidentK ^± beam the number of additional strange particles is suppressed. The results are found to be in agreement with the qualitative predictions of a parton fusion model. The comparison with the Lund model for lowp _T processes is fair.     

Systematics of exclusive diffraction dissociation modes inK ± p interactions at 32 GeV/c

We present results of an investigation of diffraction dissociation in exclusive channels inK ^± p interactions at 32 GeV/c. Total cross sections are determined forK ^±→K ^±π⁺π^?,K ^±2π⁺2π^?,K ⁰π^±π^± K ^±2π⁺π^?,K ^± K ⁺ K ^?,K ^±p \(\bar p\) , \(\bar \Lambda \) p, andp→pπ ⁺π^?,p2π⁺2π^?,pK ⁺K^?,ΛK ⁺,ΛK ⁺π⁺π^? dissociation modes, ranging from a high of ? 300 μb to ～ 3 μb. Thedσ/dt′ differential cross sections of most of the systems studied exhibit structure, with breaks of slope att′ ～ 0.2 to 0.5 GeV²; some modes have a sharp forward spike with a slope exceeding 10 GeV^?2. A systematic investigation of two-body dissociation modesK→A+B andp→A′+B′ shows that these cross sections decrease with increasing threshold massM _A+M _B, that they are comparable for kaon and proton dissociations at similar diffractive excitation masses and are systematically suppressed by a factor 3–4 for dissociations requiring an \(s\bar s\) quark pair creation when compared to \(u\bar u\) pair creation indicating a breakdown ofSU ₃ symmetry for the \(q\bar q\) sea.     

A study of multiparticle fragmentation inK + p interactions at 32 GeV/c

Results are presented on inclusive production of resonant and non-resonant particle systems produced inK ⁺ p interactions at 32 GeV/c. We compareK ^*+(892), \(\bar \Sigma ^{ * - } \) (1385), Σ^*±(1385), and ?⁰ inclusivex-spectra with the ones of non-resonantK _s ⁰ π^±, \(\bar \Lambda \pi ^ - \) , Λπ^± and π⁺π^? pairs at the same effective mass. Resonance-particle pairsK ^*+π^±, Σ^*+π^?, and \(\bar \Sigma ^{ * - } \pi ^ - \) are also studied together with non-resonant tripletsK _s ⁰ π^±, Λπ⁺π^?, \(\bar \Lambda \pi ^ - \pi ^ - \) . The invariantx-spectra of resonant particle pairs decrease less rapidly withx then the corresponding non-resonant pairs. Comparison with quark-recombination predictions indicates that the particles, resonances and multiparticle systems are probably created off a single valence quark or diquark instead of carrying all possible valence-quarks.     

Evidence for a newK * \bar K state at a mass of 1,530 MeV withIJ PC=01++ observed inK − p interactions at 4.2 GeV/c

Evidence is presented for a newK ^* \(\bar K\) +c.c. resonance with a mass of (1,526±6) MeV, a width of (107±15) MeV and quantum numbersIJ ^PC=01⁺⁺. We call itD′ meson. Initially it is observed as aK ^* \(\bar K\) +c.c. enhancement in the reactionsK ^? p→(K _s ⁰ K ^±π^?)Λ at 4.2 GeV/c. The isospin assignmentI=0 comes from its further observation in the reactionsK ^? p→(K _s ⁰ K ^±π^?)Σ ⁰ andK ^? p→(K _s ⁰ K ^±π^?)Σ(1,385)⁰ but not inK ^? p→(K ⁺ K ^?π^?)Σ⁺ orK ^? p→(K _s ⁰ K ^±π^?)Σ(1,385)⁺. A maximum likelihood analysis of the (K \(\bar K\) π) decay Dalitz plots in the reactionsK ^? p→(K _s ⁰ K ^±π^?) determines theJ ^PC of theD′ meson to be 1⁺⁺. A satisfactorySU(3) fit is obtained to a 1⁺⁺ nonet composed of theI-1A ₁, theI=1/2Q _A with theD(1,285) and theD′(1,526) as theI=0 members having a mixing angle close to the magic one.     

Measurement of the masses and lifetimes of the charmed mesonsD 0,D + andD s +

We present the final results on the measurement of the masses and lifetimes of the mesonsD ⁰,D ⁺ andD _s ⁺ in the NA32 experiment at the CERN SPS, using silicon microstrip detectors and charge-coupled devices for vertex reconstruction. We measure the following lifetimes: \(\tau _{D^0 } = 3.88 \pm _{0.21}^{0.23} \cdot 10^{ - 13} s\) using a sample of 479D°→K ^?π⁺π^?π⁺ and 162D°→K ^?π⁺ decays; \(\tau _{D^ + } = 10.5 \pm _{0.72}^{0.77} \cdot 10^{ - 13} s\) with a sample of 317D ⁺→K ^?π⁺π⁺ decays; \(\tau _{D_s^ + } = 4.69 \pm _{0.86}^{1.02} \cdot 10^{ - 13} s\) with a sample of 54D _s ⁺ →K ⁺ K ^?π⁺ decays. We measure the following masses:m _D ⁰=1864.6±0.3±1.0 MeV,m _D ⁺=1870.0±0.5±1.0 MeV and \(m_{D_s^ + } \) =1967.0±1.0±1.0 MeV.     

Two-particle production inK + p interactions at 32 GeV/c

Results are presented on two-particle inclusive production inK ⁺ p interactions at 32 GeV/c. We study thex _1,2=x ₁+x ₂ dependence of invariant structure functions of (ππ)-pairs and compare them to single particle inclusive distributions in the fragmentation regions. Distributions of particles observed at Feynmanx ₂ in association with various “trigger” particles or systems atx ₁ in the same hemisphere are dicussed in terms of the reduced variable \(\tilde x_2 = x_2 /(1 - |x_1 |)\) . We further present absolute production rates and production ratios of π⁺'s and π^?'s associated with π^±,K _s ⁰ , Λ, \(\bar \Lambda \) ,K ^*+ (890), (K _s ⁰ π⁺), and (π⁺ π^?)-triggers, and compare them with qualitative predictions of the quark recombination model. Forwardbackward correlations between (K _s ⁰ π^±), (K _s ⁰ ,p), (Λ, π^?), \((\bar \Lambda \pi ^ \pm )\) , and (p, π^?) pairs are also discussed.     

Recent Results on Hadron Spectroscopy at Belle

Recent activities of the Belle experiment in Hadron spectroscopy are presented. The discovery of two charged bottomonium-like particles, ${Z_b^{\pm}(10610)}$ and ${Z_b^{\pm}(10650)}$ in the ${\Upsilon (nS)\pi^{\pm}}$ (n = 1, 2, 3) and h _b (m P)π ^± (m = 1, 2) final states is followed by the observation of the corresponding peaks in the ${B^*\bar{B}^{(*)}}$ final states that favors the molecular interpretation of Z _b . In addition, a neutral partner candidate is explored at 10,610 MeV in the ${\Upsilon (2S)\pi^0}$ mass spectrum projection. We have got no evidence of an X(3872) partner in J/ψ π ^± π ⁰, J/ψ η and ${\chi_{c1,2}\gamma}$ final states while an evidence of the narrow peak at 3,823 MeV/c ² in ${\chi_{c1}\gamma}$ is thought to be ³ D ₂ charmonium (ψ ₂) candidate. The feasibilities of the search for X(3872) partner in the B → J/ψ π ⁰ π ⁰ K decays, the measurement of light flavored baryons production cross section, and the study of K–p interaction in ${\phi p}$ final state are also discussed.     

Analysis of experiments on the measurement of the pion electromagnetic formfactor

We analyse the experiments [1–3] on the measurement of the pion electromagnetic formfactor in the time-like and space-like region using an expression with correct analytical properties and with the asymptotics predicted by QCD. The best fit values for the physical quantities (1) electromagnetic radius of the pion:r _π ² =0.466±0.002 fm², (2) the mass and width of the ρ (770) and the ρ′ (1600) meson:m _ρ=768±1 MeV,Г _ρ=138±1 MeV,m _ρ′=1546±26 MeV,Г _ρ'=620±60 MeV; (3) the residuesg _ρ m _ρ ² =0.676±0.003,g _ρ′ m _ρ′ ² =?(0.644±0.009); (4) the ππ-scattering lengtha ₁ ¹ =(0.1±0.01)m _π ^?3 .     

Observation of a narrowK s 0 K s 0 π+π− state at 1.97 GeV produced inK + p interactions at 32 GeV/c

Evidence is provided for a new resonance in theK _s ⁰ K _s ⁰ π⁺π^? system with a mass of 1.97±0.01 GeV and width 40±20 MeV. It is produced with an inclusive cross section of ～6μb in the beam fragmentation process of 4-prongK ⁺ p interactions with at least 2 associatedV ⁰'s at 32 GeV/c and decays dominantly into theK ^{* ±} (892)K _s ⁰ π^? mode.     

Measurement ofD meson production in 200 GeV π−-Be interactions

We have measured the differential and total cross sections ofD meson production in 200 GeV π^?-beryllium interactions, using a sample of 48 fully reconstructed and nearly background-freeD mesons in the decay channelsK ^?π^±,K ^?π^±π^± andK ^?π^?π^±π^±. A single electron trigger has been used to select events containing a pair of charmed particles. A vertex telescope of 6 silison microstrip detectors allowed the reconstruction of tracks of charged secondaries and the reconstruction of primary and decay vertices with high precision. The ratio of branching fractions for \(\mathop {D^0 }\limits^{( - )} \to K^ \mp \pi ^ \pm \) to \(\mathop {D^0 }\limits^{( - )} \to K^ \mp \pi ^ \mp \pi ^ \pm \pi ^ \pm \) , and an upper limit for \(D^0 - \bar D^0 \) mixing are presented.     

Study of the centrally producedK 1 0 K ± π∓ system at 85 GeV/c

We have analyzed theK ₁ ⁰ K ^± π^? system in the reactions π⁺/pp→π⁺/p(K ₁ ⁰ K ^± π^?)p. A spin-parity analysis of theK ₁ ⁰ K ^± π^? system in the “4C” channel confirms the existence of the 1⁺⁺ E meson which decays mainly throughK ^* \(\bar K\) . The data allow the presence of a 0^?+ wave at a level of 14% of theE/ι signal. The production ofD andE mesons in the channels where theK ₁ ⁰ K ^± π^? system is produced along with a π⁰ or π⁺π^? system is suppressed.     

Partition temperature and energy conservation of particle production

The partition temperature estimated by Chou and Yang fore ⁺ e ^?→h ^± of the TASSO experiment is compared with the cm average energy of the secondaryh ^± using the MaxwellianP _⊥ distribution of invariant phase-space. Fireball properties and secondary temperatures are investigated fore ⁺ e ^?→h ^±, \(K^0 \bar K^0 \) , \(\Lambda \bar \Lambda \) of the mark II collaboration. The number of secondary particles is found to be equally divided among the central fireball and the other two of the fragmentation regions. Crucial tests based on energy conservation are carried out for temperature estimates for the Mark II data, and \(\bar pp\) →π at rest of the College de France-Cern experiment.     

Pionic deuterium

The strong-interaction shift ε _1s ^πD and broadening Γ _1s ^πD in pionic deuterium have been determined in a high statistics study of the πD(3p-1s) X-ray transition using a high-resolution crystal spectrometer. The pionic deuterium shift will provide constraints for the pion-nucleon isospin scattering lengths extracted from measurements of shift and broadening in pionic hydrogen. The hadronic broadening is related to pion absorption and production at threshold. The results are ε _1s ^πD = (?2356 ± 31) meV (repulsive) and Γ _1s ^πD meV yielding for the complex πD scattering length a _πD = [?(24.99±0.33)+i(6.22 _?0.26 ^+0.12 )] × 10^?3 m _π ^?1 . From the imaginary part, the threshold parameter for pion production is obtained to be α = (251 _?11 ⁺⁵ ) μb. This allows, in addition, and by using results from pion absorption in ³He at threshold, the determination of the effective couplings g ₀ and g ₁ for s-wave pion absorption on isoscalar and isovector NN pairs.     

A new analysis improving the evidence of a narrow peak in the invariant-mass distribution of the \Lambdap system observed in the \bar{{p}} annihilation at rest on 4He

The presence of a narrow peak in the $ \Lambda$ p invariant-mass distribution observed in the $ \bar{{p}}$ annihilation reaction at rest $\ensuremath \bar{p} {}^4\mathrm{He}\rightarrow p\pi^-p\pi^+\pi^-n X$ is discussed again through an analysis procedure which improves the ratio signal/background in comparison with the previous analysis. The peak is centred at 2223.2±3.2_stat±1.2_syst MeV and has a statistical significance of 4.7 $ \sigma$ , values compatible with those published previously. If interpreted as the result of the decay into $ \Lambda$ p of a $\ensuremath { }_{\bar{K}}{}^2\mathrm{H}$ bound system, the corresponding binding energy should be B = - 151.0±3.2_stat±1.2_syst MeV and the width $ \Gamma_{{FWHM}}^{}$ < 33.9±6.2 MeV. The production rate has a lower limit of 1.2 10^-4. Data on the $ \bar{{p}}$ annihilation reaction at rest $ \bar{{p}}$ ⁴He $ \rightarrow$ p $ \pi^{-}_{}$ p $ \pi^{-}_{}$ p _s X , analyzed for the first time, lead to a result in qualitative agreement with the previous one.     

\bar \Lambda Production inK − p interactions at 32 GeV/c

Antilambda production is studied inK ^? p interactions at 32 GeV/c. Both total and differential cross sections are presented. The inclusive \(\bar \Lambda \) production cross section amounts to 109±7 μb. A remarkable energy dependence is observed, σ( \(\bar \Lambda \) ) increasing by a factor of four between 14.3 and 32 GeV/c. Thep _⊥ ² distribution exhibits an exponential fall-off with a slope of 3.3±0.2 (GeV/c)^?2. Most of the \(\bar \Lambda \) 's are emitted in the forward hemisphere. The invariantx distribution increases between 14.3 and 32 GeV/c. Data are presented for \(\bar \Lambda \) production inK ^- p→Λ \(\bar \Lambda \) +X K ^- p→ \(\bar \Lambda \) K ⁿ +X, andK ^- p→ \(\bar \Lambda \) p+X.     

Measurement of the analyzing power of high-transverse-momentum charged hadrons in proton-nucleus collisions at an energy of 40 GeV

The transverse single-spin asymmetry was measured for charged hadrons (π ^±, K ^±, p, $\bar p$ ) produced in proton-nucleus collisions. The measurements were performed at the FODS-2 spectrometer by using a polarized proton beam that was accelerated to an energy of 40 GeV at the accelerator of the Institute for High Energy Physics (IHEP, Protvino) and which was made to hit carbon and copper nuclear targets. The data in question were obtained in the range of c.m. angles between 73° and 94° near the central region (?0.01 < x _F < 0.27, 0.7 < p _T < 3.6 GeV/c). The single-spin asymmetry for π ⁺ and K ⁺ mesons is significant at high values of p _T and moderately small positive values of x _F. The analyzing power for other hadrons (π ^?, K ^?, p, $\bar p$ ) is compatible with zero in the p _T range studied here. The dependence of the analyzing power on the mass number of the target nucleus is insignificant.     

Scaling multiplicities of h-p collisions toe + e −→π±+... by the Fermi-Landau law

The similarity of rapidity distributions of hadrons frompp and $\bar p$ p withe ⁺ e ^?→π^±+... implies a scaling forE _cm, reflecting the quark-quark interaction of particle production by $\bar p$ /p+p. This scaling relates the meson multiplicity fromh+p→m $\bar m$ +... to the Fermi-Landau law $n_{ch} = a\sqrt {E_{cm} } $ fore ⁺ e ^? collisions, without free-parameters, threshold energy being taken into account including the mass of quarks constituent of the projectile and the target, the coefficient behaves like bremsstrahlung a～1/m ².     

Inclusive single and double diffractive dissociations inK + p interactions at 32 GeV/c

We study single and double inclusive diffractive production in a 32 GeV/c K ⁺ p experiment in MIRABELLE at the Serpukhov accelerator. From reactionsK ⁺ p→K ⁺+X ⁺ andK ⁺ p→X ⁺+p we determine the total proton and kaon single diffractive dissociation cross sections \(\sigma (p\xrightarrow{{K^ + }}p_D ) = 0.90 \pm 0.12 mb\) and \(\sigma (K^ + \xrightarrow{p}K_D^ + ) = 0\) . 90±0.17 mb, respectively. In either case the only notable contributions come from dissociations into 1 and 3 charged particles. Kaon dissociation exhibits a pronounced slope-mass correlation. The search for double diffractive production in reactionsK ⁺ p→(K ⁺π^?π⁺)+X ⁺ andK ⁺ p→(pπ ⁺ π ^?)+X ⁺ leads in either case to an estimated total double diffractive cross section σ(K ⁺p→K _D ⁺ p_D) of ?220 μb. The double dissociation differential cross section exhibits a large slope of ?10GeV^?2 in the nearthreshold mass region, rapidly decreasing to ?4 GeV^?2 with increasing excitation mass. At our c.m. energy \((\sqrt s \simeq 8 GeV)\) the ratio σ_{inel dif}/σ_el is 0.85±0.10, the total diffractive cross section σ_dif≡σ_el+σ_{inel dif}=4.41±0.24 mb and the fraction σ_dif(K ⁺ p)/σ_tot(K ⁺ p) is 25±2%. TheK ⁺ andK ^? diffractive excitation mass spectra, differential cross sections and total diffractive cross sections are very similar for both single and double dissociations.     

Single-spin asymmetry for charged hadrons produced in proton-nucleus collisions at 40 GeV for c.m. production angles in the range 40°–79°

The transverse single-spin asymmetry for charged hadrons (π ^±, K ^±, p, $\bar p$ ) produced in proton-nucleus collisions was measured for c.m. production angles in the range 40°–79°. The measurements were performed with the FODS-2 setup by using a 40-GeV polarized proton beam originating from the accelerator of the Institute for High Energy Physics (Protvino) and hitting carbon and copper nuclear targets. The data in question were obtained in the polarized-proton-fragmentation region (0.0 < x _F < 0.7, 0.6 < p T < 2.5 GeV/c). In agreement with data obtained at other energies, the single-spin asymmetry for π ^± mesons is significant at high x _F. For the first time, a sizable analyzing power, which changes sign at x _F = 0.43, is observed for protons. The dependence of the analyzing power on the target-nucleus mass is insignificant.