Prompt neutrino production in a proton beam-dump experiment

In the interactions of 400 GeV/c protons with copper nuclei, a flux of prompt neutrinos is observed. The reactions produced by these neutrinos in our apparatus appear consistent with those of electron- and muon-neutrinos. The prompt neutrino fluxes are interpreted as being due to associated production and subsequent semileptonic decay of charmed hadrons. The prompt flux ratio \(\bar v_\mu /v_\mu = 0.46_{ - 0.16}^{ + 0.21} \) suggests a sizeable production of charmed baryons near the forward direction. The ratio of prompte ^?+e ⁺ toµ ^?+µ ⁺ event rates is 0.64 _?0.15 ^+0.22 , where unity is expected frome-μ universality.     

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.     

\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.     

Neutrino production of same-sign dimuons at the Fermilab Tevatron

The rate of neutrino- and antineutrino-induced prompt same-sign dimuon production in steel was measured using a sample of μ^?μ^? events and 25 μ⁺μ⁺ events withP _μ>9 GeV/c, produced in 1.5 millionv _μ and 0.3 million \(\overline {v_\mu }\) induced charged-current events with energies between 30 GeV and 600 GeV. The data were obtained with the Chicago-Columbia-Fermilab-Rochester (CCFR) neutrino detector in the Fermilab Tevatron Quadrupole Triplet Neutrino Beam during experiments E 744 and E 770. After background subtraction, the prompt rate of same-sign dimuon production is (0.53±0.24)×10^?4 perv _μ charged-current event and (0.52±0.33)×10^?4 per \(\overline {v_\mu }\) charged-current event. The kinematic distributions of the same-sign dimuon events after background subtraction are consistent with those of the non-prompt background due to meson decays in the hadron shower of a charged-current event. Calculations ofc \(\bar c\) gluon bremsstrahlung, based on improved measurements of the charm mass parameter and nucleon structure functions by the CCFR collaboration, yield a prompt rate of (0.09±0.39)×10^?4 perv _μ charged-current event. In this case,c \(\bar c\) gluon bremsstrahlung is probably not an observable source of prompt same-sign dimuons.     

Neutral strange particle production inK + p interactions at 32 GeV/c

The production properties ofK _s ⁰ , \(\bar \Lambda\) andK ⁺ p interactions at 32 GeV/c are investigated using the final statistics of the experiment. We present total and semi-inclusive cross sections and aver-age multiplicities. Estimates are given of the diffractive dissociation contributions to total and differential cross sections. Thex-,p _T ^?, and transverse mass dependence of inclusive and semi-inclusive distributions is discussed as well as properties of “prompt”K _s ⁰ 's. The ratio of “prompt”K ₈₉₀ ⁺ (K ₈₉₀ ⁰ ) to “prompt”K ⁰ cross sections is measured to be 1.03±0.12 (0.98±0.17). From a comparison of \(\bar \Lambda\) production inK ^± p interactions at 32 GeV/c, we estimate a strange sea-quark suppression of 0.26 ±0.02. The double differential cross sections ofK _s ⁰ 's is studied as a function of Feynman-x andp _T ² , and a Triple-Regge fit performed. The data are compared in detail to versions of the Lund-model for low-p _T hadronic collisions.     

A search for direct electron production inpp interactions at 70GeV/c

A search for directly produced electrons in 70 GeV/cpp interactions has been performed using BEBC equipped with a hydrogen filled track sensitive target surrounded by a hydrogen/neon blanket. No candidates for single electron production with momentump _e >500 MeV/c were found in a sample of 66,000 primary interactions. This result places an upper limit of 2.5 μb on the cross section for singlee ^± production at the 90% confidence level. The corresponding upper limit on the charmed particle production cross section in 14 μb. From the observation of 7 events producing ane ⁺e^? pair with mass, \(m_{e^ + e^ - } > m_{\pi ^0 } \) thee ^±/π^± ratio from this source is estimated to be (0.7±0.2)×10^?4.     

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.     

Production ofμ − e + pairs in neutrino interactions in the SKAT bubble chamber experiment

The production of μe-pairs is studied in interactions of neutrinos with nuclei of heavy freon in the SKAT bubble chamber experiment. A rate of μ^? e ⁺ to charged current interactions above the charm threshold of \(R^{\mu ^ - e^ + } = (4.6 \pm 1.2) \cdot 10^{ - 3} \) is found. The properties of the observed μ^? e ⁺ events can be well described by assuming them to originate from the semileptonic decay of quasielastic produced charmed baryonsΛ _c and inclusive charmedD-meson production. The rates for these reactions are found to be (6.7±3.5)×10^?2 and (2.5±0.9)×10^?2, respectively. A total charmed particle production rate of (9.2±3.6)×10^?2 is calculated.     

Feasibility studies of the time-like proton electromagnetic form factor measurements with \overline{{P}}ANDA at FAIR

The possibility of measuring the proton electromagnetic form factors in the time-like region at FAIR with the $ \overline{{P}}$ ANDA detector is discussed. Detailed simulations on signal efficiency for the annihilation of $ \bar{{p}}$ + p into a lepton pair as well as for the most important background channels have been performed. It is shown that precise measurements of the differential cross-section of the reaction $ \bar{{p}}$ + p $ \rightarrow$ e ^- + e ⁺ can be obtained in a wide kinematical range. The determination of the ratio R of the moduli of the electric and magnetic proton form factors will be possible up to a value of momentum transfer squared of q ² ? 14 (GeV/c)^2 with absolute precision from 0.01 to 0.5 (for R ～ 1 . The total $ \bar{{p}}$ + p $ \rightarrow$ e ^- + e ⁺ cross-section will be measured up to q ² ? 28 (GeV/c)^2. The results obtained from simulated events are compared to the existing data. Sensitivity to the two-photon exchange mechanism is also investigated.     

Charge radii and magnetic moments of odd- A 183-189Pb isotopes

Unexpected features of the BaBar data on e ⁺ e ^- $ \rightarrow$ B $ \overline{{B}}$ cross-sections (B stands for baryon) are discussed. These data have been collected, with unprecedented accuracy, by means of the initial-state radiation technique, which is particularly suitable in giving good acceptance and energy resolution at threshold. A striking feature observed in the BaBar data is the non-vanishing cross-section at threshold for all these processes. This is the expectation due to the Coulomb enhancement factor acting on a charged fermion pair. In the case of e ⁺ e ^- $ \rightarrow$ p $ \overline{{p}}$ it is found that Coulomb final-state interactions largely dominate the cross-section and the form factor is | G ^p(4M ² _p)| ～ 1 , which could be a general feature for baryons. In the case of neutral baryons an interpretation of the non-vanishing cross-section at threshold is suggested, based on quark electromagnetic interaction and taking into account the asymmetry between attractive and repulsive Coulomb factors. Besides strange baryon cross-sections are compared to U -spin invariance predictions.     

Baryon pairs production ine + e − annihilation at\sqrt s = 2.4 GeV

Search for baryon pairs production ine ⁺ e ^? annihilation at \(\sqrt s = 2386 MeV\) is reported. The data relate to a luminosity of 161 nb^?1 collected by the DM2 experiment at DCI, the Orsay colliding ring. First measurements of directe ⁺ e ^? annihilation into \(\Lambda \bar \Lambda \) and ofe ⁺ e ^?→ \(p\bar p\) at this energy are presented. First observation of a goode ⁺ e ^?→ \(n\bar n\) candidate is reported and upper limits are given fore ⁺ e ^?→ \(n\bar n, \Lambda \bar \sum ^0 + c.c.\) and \(\Sigma ^0 \bar \Sigma ^0 \) .     

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.     

Inclusive ϕ production inK − p interactions at 110 GeV/c and search for structure in φ π−

Results on inclusive ? production inK ^? p interactions at 110 GeV/c are presented. The production cross section is found to be larger than in πp andpp interactions at similar energies, suggesting OZI allowed \(s\bar s\) fusion to be the dominant mechanism in ? production. Thex distributions of ? and \(\bar K^{*0} \) are found to be similar to each other over the entirex range suggesting an overall strangeness suppression factor of 0.20±0.04 in the sea to be the dominant source of the difference in the cross section for ? and \(\bar K^{*0} \) . There is no evidence of a narrowφπ ^? state around 2.1 GeV/c² as suggested byK ⁺ experiments, but there is some excess of events in the region 1.94?1.98 GeV/c² consistent with theF-meson mass as observed ine ⁺ e ^? experiments.     

Ξ Resonances in Ξ− Be interactions II. Properties of Ξ(1820) and Ξ(1960) in the\Lambda \bar K^0 and\Sigma ^0 \bar K^0 channels

In an experiment at the CERN-SPS charged hyperon beam, we have investigated the inclusive \(\Lambda \bar K^0 \) and \(\Sigma ^0 \bar K^0 \) final states formed in Ξ^? Be interactions. In the \(\Lambda \bar K^0 \) channel, we observe a signal at 1826 MeV/c² which can be identified with the known Ξ(1820) resonance. We determine its mass and width to be:M=1826±4 MeV/c², Г=12±14 MeV/c². A moment analysis is consistent with a spin of 3/2 and indicates a negative parity for this spin assignment. Also in the \(\Lambda \bar K^0 \) channel, we observe a 3.6σ signal with the following parameters:M=1963±5 MeV/c², Г=25±15 MeV/c². This state, which we call Ξ(1960), is not observed in the \(\Sigma ^0 \bar K^0 \) channel, leading to an upper limit on the ratio of partial widths \(\Sigma \bar K/\Lambda \bar K\) of 2.3 (90% confidence level). A moment analysis of the \(\Lambda \bar K^0 \) final state indicates a spin of 5/2 or greater in the natural spin-parity series 5/2⁺, 7/2^?, etc.     

Determination of the effective number of light strongly interacting fermions frome + e − data

Both the topology of hadronic final states ine ⁺ e ^? collisions and the evolution of event shape distributions with center of mass energy depend on the total numberN of light fermion species which couple to gluons. From an analysis ofe ⁺ e ^? data between \(\sqrt s = 14\) GeV and \(\sqrt s = 91\) GeV I determineN=6.3±1.1. This result is compatible with both the Standard Model expectation of 5 and with the existence of a light gluino, in which caseN would be about 8.     

On the semileptonic decay distributions from the next heavy quark

Motivated by the discovery of λ(9.4), we study the semileptonic decay correlations of the next heavy quark, and their consequences for thee ⁺ e ^? colliding beam and neutrino experiments. A detailed comparison is made with the corresponding correlations from the production and decay of charm and heavy leptons, τ^±. Some tests of the \({\rm B}^0 - \bar {\rm B}^0 \) mixing ( \(B = b\bar q\) withbaQ=?1/3 heavy quark) are suggested fore ⁺ e ^? colliding beam experiments.     

Final results on μe-pair production in neutrino interactions in the SKAT freon bubble chamber experiment

We present the final results from the search for μe pairs produced in neutrino interactions using the freon filled bubble chamber SKAT. The rate of μ^? e ⁺ pairs to charged current events above the charm threshold is \(R_{\mu ^ - e^ + } = (4.8 \pm 1.1)10^{ - 3} \) . Assuming charm particle production to be the origin of the positron we calculate \(R_{\Lambda _c^ + } = (6.2 \pm 3.1)10^{ - 2} \) andR _D =(2.8±0.9)10^?2. We observe no considerable μ^? e ^? pair production above the background. In the regionE _v >3 GeV,p _μ,e >1.0 GeV/c andp _μ>p _e we find with a 90% confidence level the limit \(R_{\mu ^ - e^ - }< 1.7 10^{ - 4} \) .     

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.     

Charged multiplicities of hadrons in hadronic and leptonic reactions

Experimental data on average charged multiplicities of hadrons produced ine ⁺ e ^? annihilations,v N and \(\bar vN\) reactions and non-diffractive π^± p andpp interactions over a wide energy range are found to satisfy simple relationships obtained by expressing the multiplicity of each reaction as a sum of single-quark and diquark jet multiplicities. The observed difference between these two terms can be attributed to the leading nucleon effect.     

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.