A search for double- Λ hypernuclei ( 12 ΛΛ Be) and H -dibaryons using the 12 C( K − , K + ) reaction was performed at the BNL-AGS using a high-intensity 1.8 GeV/ c K − beam. A missing-mass analysis below the end point of the quasi-free Ξ − production was used to investigate these S =−2 systems. The upper limit obtained for the forward-angle cross section of 12 ΛΛ Be production is 6 to 10 nb/sr. This is the first search for the direct production of double- Λ hypernuclei to reach the sensitivity required to observe the signal predicted by theoretical calculations. For the H -production cross section, we have obtained an upper limit in the range of a few nb/sr to 10 nb/sr for the H mass below 2100 MeV/ c 2 . This upper limit is the most sensitive H search result to date for a tightly bound H .
Upper limit is given.
The production of the H-dibaryon could occur via the (K-, K+) reaction on two protons in a nucleus: K- (PP) --> K+ H-dibaryon. Upper limit is given.
Spectra of positively charged kaons in p+C interactions at 31 GeV/c were measured with the NA61/SHINE spectrometer at the CERN SPS. The analysis is based on the full set of data collected in 2007 with a graphite target with a thickness of 4% of a nuclear interaction length. Interaction cross sections and charged pion spectra were already measured using the same set of data. These new measurements in combination with the published ones are required to improve predictions of the neutrino flux for the T2K long baseline neutrino oscillation experiment in Japan. In particular, the knowledge of kaon production is crucial for precisely predicting the intrinsic electron neutrino component and the high energy tail of the T2K beam. The results are presented as a function of laboratory momentum in 2 intervals of the laboratory polar angle covering the range from 20 up to 240 mrad. The kaon spectra are compared with predictions of several hadron production models. Using the published pion results and the new kaon data, the K+/\pi+ ratios are computed.
The measured K+ production cross section and the K+/PI+ cross section ratio for the angular range 20 to 140 mrad. The errors on the ratios are statistical only.
The measured K+ production cross section and the K+/PI+ cross section ratio for the angular range 140 to 240 mrad. The errors on the ratios are statistical only.
We study the processes $e^+ e^-\to K_S^0 K_L^0 \gamma$, $K_S^0 K_L^0 \pi^+\pi^-\gamma$, $K_S^0 K_S^0 \pi^+\pi^-\gamma$, and $K_S^0 K_S^0 K^+K^-\gamma$, where the photon is radiated from the initial state, providing cross section measurements for the hadronic states over a continuum of center-of-mass energies. The results are based on 469 fb$^{-1}$ of data collected with the BaBar detector at SLAC. We observe the $\phi(1020)$ resonance in the $K_S^0 K_L^0$ final state and measure the product of its electronic width and branching fraction with about 3% uncertainty. We present a measurement of the $e^+ e^-\to K_S^0 K_L^0 $ cross section in the energy range from 1.06 to 2.2 GeV and observe the production of a resonance at 1.67 GeV. We present the first measurements of the $e^+ e^-\to K_S^0 K_L^0 \pi^+\pi^-$, $K_S^0 K_S^0 \pi^+\pi^-$, and $K_S^0 K_S^0 K^+K^-$ cross sections, and study the intermediate resonance structures. We obtain the first observations of \jpsi decay to the $K_S^0 K_L^0 \pi^+\pi^-$, $K_S^0 K_S^0 \pi^+\pi^-$, and $K_S^0 K_S^0 K^+K^-$ final states.
Cross section measurement for PHI(1020).
Mass measurement for PHI(1020).
Measurement of the PHI(1020) width.
From a sample of about 75000 τ decays identified with the ALEPH detector, K 0 production in 1-prong hadronic decays is investigated by tagging the K L 0 component in a hadronic calorimeter. Results are given for the final states ν τ h − K 0 and ν τ h − π 0 K 0 where the h − is separated into π and K contributions by means of the dE / dx measurement in in the central detector. The resulting branching ratios are: ( Bτ → ν τ π − K 0 ) = (0.88±0.14±0.09)%, ( Bτ → ν τ K − K 0 ) = (0.29±0.12±0.03)%, ( Bτ → ν τ π − π 0 K 0 ) = (0.33±0.14±0.07)% aand ( Bτ → ν τ K − π 0 K 0 ) = (0.05±0.05±0.01)%. The K ∗ decay rate in the K 0 π channel agrees with that in the Kπ 0 mode: the combined value for the branching ratio is (Bτ → ν τ K ∗− ) = (1.45±0.13±0.11)% .
Invariant mass distribution for the $K^0\pi$ system data. The numbers have been read from the plot in the paper.
We have measured pi+pi- and K+K- production in two-photon collisions using 87.7 /fb of data collected with the Belle detector at the asymmetric energy e+e- collider KEKB. The cross sections are measured to high precision in the two-photon center-of-mass energy (W) range between 2.4 GeV < W < 4.1 GeV and angular region |cos theta^{*}| < 0.6. The cross section ratio sigma(gammagamma->K+K-)/sigma(gammagamma->pi+pi-) is measured to be 0.89 +- 0.04(stat) +- 0.15(syst) in the range of 3.0 GeV < W < 4.1 GeV, where the ratio is energy independent. We observe a sin^{-4} theta^{*} behavior of the cross section in the same W range. Production of chi_{c0} and chi_{c2} mesons is observed in both gammagamma -> pi+pi- and gammagamma -> K+K- modes.
Cross sections for PI+ PI- and K+ K- production.
Ratio of K+ K- to PI+ PI- production in the region of W from 3.0 to 4.1 GeV, where the ratio is energy independent.
Angular dependence of the normalized differential cross section, $\sigma_0^{-1}{\rm d}\sigma/{\rm d}|\cos\theta^*|$, for the $\pi^+\pi^-$ process. The errors are statistical only.
Form a sample of about 75000 τ decays measured in the ALEPH detector, 1-prong charged kaon decays are identified by the dE / dx measurement in the central detector. The resulting branching ratios for the inclusive and exclusive modes are: B ( τ → ν τ K − ≥ 0 π 0 ≥ 0 K 0 ) = (1.60±0.07±0.12)%, B ( τ → ν τ K − = (0.64±0.05±0.05)%, B ( τ → ν τ − π 0 = (0.53±0.05±0.07)% and B ( τ → ν τ K − π 0 π 0 ) = (0.04±0.03±0.02)%. Exclusive modes are corrected for measured K L 0 production. The rate for τ → ν τ K − agrees well with the prediction based on τ - μ universality.
Invariant mass distribution of the $K\pi^0$ final state, as obtained from a $dE/dx$ fit in each mass bin. The numbers have been read from the plot in the paper, with the errors simply set to zero if they are smaller than the point size.
The decay B0 -> J/psi K0_S is reconstructed with J/psi -> e+ e- or mu+ mu- and K0_S -> pi+ pi-. From the full ALEPH dataset at LEP1 of about 4 million hadronic Z decays, 23 candidates are selected with an estimated purity of 71%. They are used to measure the CP asymmetry of this decay, given by sin 2beta in the Standard Model, with the result sin 2beta = 0.84 +0.82-1.04 +-0.16. This is combined with existing measurements from other experiments, and increases the confidence level that CP violation has been observed in this channel to 98%.
Standard Model predicts the time-dependent rate asymmetry as follows: A(t) = (B0(t)-BBAR0(t))/(B0(t)+BBAR0(t)) = SIN(2*BETA)*SIN(Delta(M)*t), where Delta(M) is the mass difference between the two B0 mass eigenstates.
The reactions ee->ee+pi0+X and ee->ee+K0s+X are studied using data collected at LEP with the L3 detector at centre-of-mass energies between 189 and 202 GeV. Inclusive differential cross sections are measured as a function of the particle transverse momentum pt and the pseudo-rapidity. For pt < 1.5 GeV, the pi0 and K0s differential cross sections are described by an exponential, typical of soft hadronic processes. For pt > 1.5 GeV, the cross sections show the presence of perturbative QCD processes, described by a power-law. The data are compared to Monte Carlo predictions and to NLO QCD calculations.
The PI0 differential cross section as a function of PT.
The PI0 differential cross section as a function of pseudorapidity.
The K0S differential cross section as a function of PT.
Exclusive production of π and K meson pairs in two photon collisions is measured with ALEPH data collected between 1992 and 2000. Cross-sections are presented as a function of cos θ ∗ and invariant mass, for | cos θ ∗ |<0.6 and invariant masses between 2.0 and 6.0 GeV/ c 2 (2.25 and 4.0 GeV/ c 2 ) for pions (kaons). The shape of the distributions are found to be well described by QCD predictions but the data have a significantly higher normalization.
Measured angular distribution for pion production.
Measured angular distribution for kaon production.
Measured cross section for pion production as a function of W.
A measurement of Λ c + production in neutrino nucleon charged-current interactions is presented. In a subsample of about 50 000 interactions located in the emulsion target of the CHORUS detector, exposed to the wide band neutrino beam of the CERN SPS, candidates for decays of short-lived particles were identified using new automatic scanning systems and later confirmed through visual inspection. Criteria based on the flight length allowed a statistical separation among the different charm species thus enabling a sample particularly rich in Λ c + to be defined. At an average neutrino energy of 27 GeV, the product σ (Λ c + )/ σ (CC)× BR (Λ c + →3 p ) was measured to be (0.37±0.10(stat)±0.02(syst))×10 −2 , while the values of (1.54±0.35(stat)±0.18(syst))×10 −2 and of 0.24±0.07(stat)±0.04(syst) were obtained for σ (Λ c + )/ σ (CC) and BR (Λ c + →3 p ), respectively.
LAMBDA/C+ cross sections relative to the CC cross section.
LAMBDA/C+ cross sections relative to the CC cross section.
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