Kaon Beam Research Articles

Measurement of the Lambda -->n+ gamma branching ratio.

The branching ratio for the \ensuremath{\Lambda} weak radiative decay has been measured to be B(\ensuremath{\Lambda}\ensuremath{\rightarrow}n+\ensuremath{\gamma})/(\ensuremath{\Lambda}\ensuremath{\rightarrow}anything) =[1.78\ifmmode\pm\else\textpm\fi{}0.24(stat)${\ifmmode\pm\else\textpm\fi{}}_{0.16}^{0.14}$(syst)]\ifmmode\times\else\texttimes\fi{}${10}^{\mathrm{\ensuremath{-}}3}$. A low-energy kaon beam was used to produce the \ensuremath{\Lambda} hyperons via the reaction ${\mathit{K}}^{\mathrm{\ensuremath{-}}}$+p\ensuremath{\rightarrow}\ensuremath{\Lambda}+${\mathrm{\ensuremath{\pi}}}^{0}$ at rest. Photons from the signal channel and ${\mathrm{\ensuremath{\pi}}}^{0}$ decay were detected with a NaI(Tl) array. The final spectrum contains 287 events after background subtraction, an order of magnitude more events than from the only previous measurement.

Phenomenology of the neutral-kaon system in the presence of CPT noninvariance

I elaborate a phenomenology of the neutral-kaon system in which CPT invariance is not assumed and no phase conventions are done. I emphasize that, if there is CPT noninvariance, high-precision experiments with kaon beams which at the production moment are either pure K 0 or pure K 0¯ are crucial. I pay special attention to the different possibilities for measuring the T- and CPT-violation parameters in the neutral-kaon mass matrix, and also the ΔS = − ΔQ parameters of the semileptonic decays.

Direct tests of CPT and T invariance in the neutral-kaon mass matrix.

I suggest a possible way of measuring the {ital T}- and {ital CPT}-violating parameters in the neutral-kaon mass matrix, which makes use of their influence on, respectively, the difference of normalization and the difference of shape of the decay curves, to an arbitrary channel {ital c} of kaons and antikaons. This method is alternative to the direct study of the neutral-kaon oscillations. Both require kaon beams with well-defined strangeness.

Inclusive photoproduction of single charged particles at highp T

Single charged-particle inclusive cross sections for photon, pion and kaon beams on hydrogen at the CERN-SPS are presented as functions ofp T andx F . Data cover the range 0.0<p T <5.0 GeV/c and 0.0<x F <1.0 at incident momenta from 70 to 170 GeV/c. The comparison between photon- and hadron-induced data indicates a relative excess of particles withp T >1.6 GeV/c for the photon-induced data. Using the hadron-induced data to estimate the hadronic behaviour of the photon, the difference distributions and ratios of cross sections are a measure of the contribution of the point-like photon interactions. The data are compared with QCD calculations and show broadly similar features.

Hadron spectroscopy

A European Hadron Facility providing intense beams of pions, kaons, and protons would have a stimulating impact on hadron spectroscopy. Typical examples of present-day discussions in meson and baryon spectroscopy are outlined. The new low-mass neutral particle possibly found in heavy-ion collisions is used to demonstrate that new accelerators may uncover unexspected physics.

Meson-nucleus interaction - on the use of intensive meson beams for subnuclear research -

The use of intensive pion and kaon beams for subnuclear research is discussed. The goals of such investigations are briefly sketched and illustrated for some typical examples of specific flavour transfer reactions. It turns out that the meson beams which will be available at the proposed EHF will open up a new aera of subnuclear research. Such investigation touch upon quite fundamental questions of hadronic physics.

Cloud pions

A Monte Carlo program has been written to calculate the spectrum and effective source size of the pions produced by K S 0 decay (“cloud pions”). It is concluded that these pions make a significant contribution to the contamination observed at the end of low momentum (∼ 0.5 GeV/c) kaon beam lines.

Beams for kaon research

A proposed 1–2 GeV/c kaon beam line for BNL, designed to deliver momentum analyzed negative kaon beams with intensities above 10 6 per spill, is discussed. The beam intensity is expected to be about an order of magnitude greater than presently available and it is expected to be a clean beam with no more than 1:1 ( π −, μ −, e −)/K −. The beam line will allow a detailed investigation of strangeness −2 systems as well as continued investigations of strangeness −1 systems.

S = −1 dibaryon production with kaon beams

Production cross sections for strangeness S = −1 six-quark dibaryon states D s,t in the (K −, π ±) reactions on deuterium and 3He targets have been estimated. For the lowest-lying configurations (mass range 2100–2200 MeV in the MIT bag model) of quark structure Q 4 − Q 2, namely 1P 1 and 3P J , peak differential cross sections of order 1 μb/sr are predicted. The angular distributions are peaked in the region of 20° ⩽ θ ⩽ 30°, characteristic of angular momentum transfer ΔL = 1. We evaluate the prospects for detecting a dibaryon signal in the presence of background processes such as d( K −, π −) YN or 3 He( K −, π +)Σ − pn .

ASTOR, Concept of a Combined Acceleration and Storage Ring for the Production of Intense Pulsed or Continuous Beams of Neutrinos, Pions, Muons, Kaons and Neutrons

A new concept for a high intensity accelerator for 2 GeV protons using the continuous 590 MeV beam from the present ring cyclotron has been worked out at SIN. To suppress the cosmic background in neutrino experiments a pulsed beam with high peak current and low duty cycle is required. Using the so called phase expansion effect one can combine the acceleration and storage effect in a single isochronous cyclotron ASTOR. With the help of several RF cavities, positioned at different radii it is possible to operate ASTOR either in a pulsed mode at 1500 Hz or in a continuous mode. The anticipated beam powers are .8 MW and 4 MW respectively. The ASTOR concept is also applicable in a possible kaon factory design, acting as an interface between the SIN ring cyclotron and a 50 Hz synchrotron for 15 to 20 GeV protons.

Kaon Factories

Kaon factories would provide beams 100-1000 times more intense than those available from present accelerators in the 10-30 GeV range. More intense or cleaner secondary beams of kaons, antiprotons and neutrinos would be of particular interest for high precision experiments and studies of rare processes in both particle and nuclear physics, e.g. symmetry violations in K-decay, neutrino scattering, meson and baryon spectroscopy, hypernuclei, exotic atoms, K <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">+</sup> studies of nuclear density and resonance propagation in nuclei. The various accelerators proposed include both fastcycling synchrotrons providing 100 μA proton beams at 15 to 32 GeV and superconducting isochronous ring cyclotrons giving 100-400 μA at up to 15 GeV. This paper describes these designs and the various technical problems associated with them.

Low Momentum Kaon Beam Lines

Current low momentum (≳500 MeV/c) high acceptance (≳5 msr) kaon beam lines feature high ratios of charged contaminant particles to kaons. The results of computer calculations on scattering and pion production from K <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">0</sup> <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">S</sub> decay are presented to indicate some of the sources of this contamination. Criteria for the design of beam lines are discussed and a new beam line design is proposed.

Glueballs, multiquark states and the OZI rule

New signatures for detection of non-quarkonium mesons are considered, including K +K + π + π − and K SK S π + π + decays for states where K +K + and K +K ∗+ decays are forbidden, and A-dependence of S ∗ and δ production on nuclei by kaon beams. Analysis of OZI rule shows that only selection rules forbidding hairpin diagrams are valid and that φφ production by pion beams is not a serious OZI violation indicating presence of glueballs.

The low energy well enriched kaon beam K2 at the KEK 12 GeV proton synchrotron

The design and performance of the low energy kaon beam K2 are described. It has been constructed to provide a well enriched kaon beam with a momentum region of 1–2 GeV/c at the KEK 12 GeV proton synchrotron. It consists of thirteen magnets and an electrostatic separator. The beam acceptance and the beam length are 6.25 msr.% Δp/p and 27.9 m, respectively. Beam intensities of 5 × 105 K+ and 1 × 105 K− were obtained at a beam momentum of 2.1 GeV/c for 1012 12 GeV primary protons incident on a 6 mm diam, and 60 mm long platinum target. The π+/K+ ratio measured was about 2 at a beam momentum of 1.6 GeV/c.

Low-pThadron production and a valon-parton recombination model

We apply a variant of the recombination model which we call the ''valon-parton model'' simultaneously to a variety of meson inclusive reactions with proton, pion, and kaon beams in the kinematic region of low transverse momentum and intermediate values of longitudinal-momentum fractions. We find that the valon distributions in hadrons show no evidence for SU(3) breaking. There are some indications of substantial gluon-dissociation contributions which we interpret through a ''maximally enhanced sea.'' For proton-induced reactions the model predictions are in excellent agreement with data; meson-induced reactions indicate additional contributions are coming from resonances which are produced recombinantly and then decay into the observed mesons.

Soft corrections to the Drell-Yan process in QCD

The infrared corrections to the Drell-Yan process are studied to all orders in QCD. Our results show that higher-order terms slightly modify the first-order corrections in the range of τ experimentally accessible in proton-proton collisions. Accurate measurements with pion and kaon beams should, however, reveal the increase with τ of the soft corrections.

Inclusive π0 and η production from kaon, proton and antiproton beams in the triple-Regge region

Data are presented on the reactions K ±p → π 0X, K ±p → ηX, pp → π 0X and pp → π 0 X in the kinematic region with s ⋍ 200 GeV 2, x ≳ 0.7 and − t ≲ 1 GeV 2. The data agree well with the predictions of triple-Regge theory and the K ∗ and nucleon Regge trajectories extracted from the data agree with the linear trajectories extrapolated from the particle poles.

Meson Structure Functions from High-Transverse-Momentum Hadron Interactions

Data on large--transverse-momentum ..pi../sup 0/ production by proton, pion, and kaon beams is used to extract the large-x behavior of meson structure functions. Good agreement is found with the proton and pion quark distribution functions obtained from deep inelastic and dimuon production experiments. This study provides the first look at the kaon structure function. A significantly faster falloff is found as x approaches unity than for that of pions.

Observation of kaonic hydrogen atom X-rays

A special liquid-hydrogen target has been used with a stopping kaon beam in order to search for the X-rays from kaonic hydrogen atoms. A peak at 6.52 ± 0.06 keV, consistent with the unshifted energy of 2p-1s X-rays from K −−p atoms, has been observed with a yield of about 0.1%. The energy shift would imply rather small values for the real K −−p scattering length at threshold.

Low Energy Kaon Beam Lines at KEK

The results of the measurements of the characteristics of two low energy separated beams, K2 and K3, are reported. The performances of the electrostatic separators used in those beams are also presented.