Search

We present the analysis of 64 000 K/sup -/p..--> sigma../sup -/..pi../sup +/ and 89 000 K/sup -/p..--> sigma../sup +/..pi../sup -/ events obtained with the Berkeley 25-in. hydrogen bubble chamber. Total cross sections and Legendre-polynomial expansion coefficients describing the differential cross sections and polarizations are presented in 10-MeV/c momentum intervals extending from 220 to 470 MeV/c. This paper completes the series devoted to all K/sup -/p final states in this momentum range.

A measurement of the spatial resolution of a liquid-argon filled chamber was performed with minimum ionizing particles. Two multi-strip chambers with 20-{micro}m strip spacing operating in the ionization mode were used in the experiment. They perform in accordance with a simple model based on electron diffusion. An estimate of the amount of electron diffusion in liquid argon is given and the time jitter distribution has a FWHM of 200 ns. Under best conditions, the spatial resolution is better than 20 {micro}m rms with an efficiency of nearly 100%.

We have studied ${K}^{+}{\ensuremath{\pi}}^{\ensuremath{-}}$ elastic scattering in the reaction ${K}^{+}p\ensuremath{\rightarrow}{K}^{+}{\ensuremath{\pi}}^{\ensuremath{-}}{\ensuremath{\Delta}}^{++}$ at $12 \frac{\mathrm{GeV}}{c}$ and in the $K\ensuremath{\pi}$ mass interval 800 to 1000 MeV. We have performed a partial-wave analysis in this $K\ensuremath{\pi}$ mass region, dominated by the $p$-wave resonance ${K}^{*}(890)$, in order to obtain information about the $s$-wave amplitude. We have extrapolated the ${K}^{+}{\ensuremath{\pi}}^{\ensuremath{-}}$ moments, the total cross section, and $p$-wave cross section to the pion pole. The $p$-wave cross section is close to the unitarity limit and can be described by a Breit-Wigner resonance form, with parameters $M=896\ifmmode\pm\else\textpm\fi{}2$ MeV and $\ensuremath{\Gamma}=47\ifmmode\pm\else\textpm\fi{}3$ MeV. We then perform an energy-independent phase-shift analysis of the extrapolated moments and total cross section using this Breit-Wigner form for the $p$ wave and a previously determined small negative phase shift for the $I=\frac{3}{2}s$ wave. For the $I=\frac{1}{2}s$-wave phase shift we find the so called "down" solution, which has a phase shift that rises slowly from 20\ifmmode^\circ\else\textdegree\fi{} at $M(K\ensuremath{\pi})=800$ MeV to 60\ifmmode^\circ\else\textdegree\fi{} at $M(K\ensuremath{\pi})=1000$ MeV. The energy dependence of this phase shift is well described by an effective range form, with a scattering length ${a}_{0}^{1}=\ensuremath{-}0.33\ifmmode\pm\else\textpm\fi{}0.05$ F. The so-called "up" solution is eliminated or has large ${\ensuremath{\chi}}^{2}$ everywhere except for two overlapping mass intervals at $M(K\ensuremath{\pi})=890 \mathrm{and} 900$ MeV. However, due to limited statistics, we expect two solutions for the $s$ wave very near the mass where the $p$ wave is resonant. We then perform an energy-dependent partial-wave analysis and find again no evidence for an $s$-wave resonance although, due to limited statistics, we could not exclude one at 890 MeV with $\ensuremath{\Gamma}l7$ MeV.

Using the Fermilab 15-ft neon-hydrogen bubble chamber we have identified seventeen events of the type ..nu../sub ..mu../N ..-->.. ..mu../sup -/e/sup +/X. The ratio of the production of these events to ordinary neutrino charged-current events is (7.7 +- 3.0) x 10/sup -3/ for positron energy greater than 800 MeV and neutrino energy greater than 10 GeV. Associated with these seventeen events are 11 V's, of which eight fit K/sub s//sup 0/ ..-->.. ..pi../sup +/..pi../sup -/ and three fit K/sub s//sup 0/ ..-->.. ..pi../sup +/..pi../sup -/ and ..lambda.. ..-->.. p..pi../sup -/ ambiguously. The average K/sup 0/ multiplicity per ..mu../sup -/e/sup +/ event is determined to be 1.84/sup +0.63//sub -0.53/.

An external muon identifier to aid in the identification of muons produced in neutrino interactions in the Fermilab 15 ft bubble chamber has been constructed. Details of design and analysis procedures are discussed. The spatial resolution and efficiency have been calibrated using muons regenerated by neutrino interactions in material upstream of the bubble chamber. A formalism to describe the statistical significance of muon matches in the identifier is developed and tested using tracks from actual neutrino interactions.

An analysis has been made of 64600 events of the type K/sup -/p ..-->.. K/sup -/p and 22800 events of the type K/sup -/p ..-->.. K/sup 0/n in the Berkeley 25-in. hydrogen bubble chamber. Differential cross sections have been measured in intervals of 10 MeV/c over the momentum range 220 to 470 MeV/c. Legendre-polynomial fits to the distributions have been made, and the coefficients show structure from the resonant D-wave ..lambda..(1520) and background S and P waves. No new structure is observed. The total K/sup -/p cross section determined from measurements of all final states seen in this exposure is also presented. (AIP)

We present results of an energy-dependent phase-shift analysis for ππ energies between 550 and 1150 MeV from reactions π+p→π+π−Δ++ and π+p→K+K−Δ++ at 7.1 GeV/c. The I=0 s wave is parametrized in terms of a 2 × 2 M-matrix coupling ππ and KK¯ channels. All the obtained solutions rule out the possibility of a narrow e resonance in the ρ region and are characterized by a very rapid variation of the I=0 s-wave amplitude near KK¯ threshold. We show that this rapid variation can be explained by a pole in the second Riemann sheet close to the KK¯ threshold.

An anomaly at 980 MeV is seen in both the mass distribution and angular distribution of the π + π − system produced in the reaction π + p → Δ ++ π + π − at 7 GeV/ c . Experimental results for the related final states Δ ++ K + K − , Δ ++ π + π − π + π − and Δ ++ π + π − (neutrals) are presented.

We present experimental distributions for the reactions K+p → pK+φ, φ → K−K+ and K+p → pK+ω, ω → π−π+π0 at 12 GeV/c. The data were obtained from a 35 events/μb exposure of the SLAC 82-inch HBC. The cross sections for these reactions are (11 ± 1) μb and (47 ± 3) μb. We observe Kφ, Kω, and pω low-mass enhancements with no evidence for narrow structure. The momentum-transfer and angular-decay spectra of these systems are presented.

An experiment to study the decay ${\ensuremath{\Sigma}}^{+}\ensuremath{\rightarrow}p\ensuremath{\gamma}$ was performed in the Berkeley 25-in. hydrogen bubble chamber. An analysis was made of 48 000 events of the type ${K}^{\ensuremath{-}}p\ensuremath{\rightarrow}{\ensuremath{\Sigma}}^{+}{\ensuremath{\pi}}^{\ensuremath{-}}$, ${\ensuremath{\Sigma}}^{+}\ensuremath{\rightarrow}p+\mathrm{neutral}$ with ${K}^{\ensuremath{-}}$ momenta near 400 MeV/c. The $\ensuremath{\Sigma}'\mathrm{s}$ produced in this momentum region are polarized because of the interference of the ${{Y}_{0}}^{*} (1520)$ amplitude with the background amplitudes. We have measured the proton asymmetry parameter $\ensuremath{\alpha}$ for 61 ${\ensuremath{\Sigma}}^{+}\ensuremath{\rightarrow}p\ensuremath{\gamma}$ events with an average polarization of 0.4. We found $\ensuremath{\alpha}=\ensuremath{-}{{1.03}_{\ensuremath{-}0.42}}^{+0.52}$. $\mathrm{SU}(3)$ predicts a value $\ensuremath{\alpha}=0$. A more restricted sample of events was used to determine the ${\ensuremath{\Sigma}}^{+}\ensuremath{\rightarrow}p\ensuremath{\gamma}$ branching ratio. From 31 ${\ensuremath{\Sigma}}^{+}\ensuremath{\rightarrow}p\ensuremath{\gamma}$ events and 11 670 ${\ensuremath{\Sigma}}^{+}\ensuremath{\rightarrow}p{\ensuremath{\pi}}^{0}$ events, we found $\frac{({\ensuremath{\Sigma}}^{+}\ensuremath{\rightarrow}p\ensuremath{\gamma})}{({\ensuremath{\Sigma}}^{+}\ensuremath{\rightarrow}p{\ensuremath{\pi}}^{0})}=(2.76\ifmmode\pm\else\textpm\fi{}0.51)\ifmmode\times\else\texttimes\fi{}{10}^{\ensuremath{-}3}$. The result is in agreement with the previous measurements.

We have studied the time distributions of 242 leptonic decays of neutral $K$ mesons produced in the reaction ${K}^{\ensuremath{-}}+p\ensuremath{\rightarrow}{\overline{K}}^{0}+n$. For the $\ensuremath{\Delta}S=\ensuremath{-}\ensuremath{\Delta}Q$ parameter $x$ we find $\mathrm{Re}(x)={0.22}_{\ensuremath{-}0.09}^{+0.07}$, $\mathrm{Im}(x)=\ensuremath{-}0.88\ifmmode\pm\else\textpm\fi{}0.08$.

Author(s): Davis, Philip J.; Alston-Garnjost, Margaret; Barbaro-Galtieri, Angela.; Flatte, Stanley M.; Friedman, Jerome H.; Lynch, Gerald R.; Rabin, Monroe S.; Solmitz, Frank T.

The observed branching fractions of the A 2 + produced in the reaction π + p→A 2 + p at 7 GeV/ c and decaying to ϱπ, ηπ, K K and η′π are presented. The data show no convincing evidence for the decay A 2 + → η ′ π + , the branching fraction being less than 3%. For the other decay modes the values obtained for ϱπ, ηπ and K K are 0.744 ± 0.029, 0.183 ± 0.026 and 0.072 ± 0.012 respectively.

Author(s): Davis, Philip J.; Derenzo, Stephen E.; Flatte, Stanley M.; Garnjost, Margaret A.; Lynch, Gerald R.; Solmitz, Prank T.

The rate for the decay $\ensuremath{\Lambda}(1520)\ensuremath{-}\ensuremath{\Sigma}(1385)\ensuremath{\pi}$ has been measured in a study of the reaction sequence ${K}^{\ensuremath{-}}p\ensuremath{\rightarrow}\ensuremath{\Lambda}(1520)\ensuremath{\rightarrow}\ensuremath{\Sigma}(1385)\ensuremath{\pi}\ensuremath{\rightarrow}\ensuremath{\Lambda}{\ensuremath{\pi}}^{+}{\ensuremath{\pi}}^{\ensuremath{-}}$. A sample of 9200 events of the type ${K}^{\ensuremath{-}}p\ensuremath{\rightarrow}\ensuremath{\Lambda}{\ensuremath{\pi}}^{+}{\ensuremath{\pi}}^{\ensuremath{-}}$ has been obtained in the Berkeley 25-in. hydrogen bubble chamber. The incident momenta range from 300 to 470 MeV/c. An energy-independent partial-wave analysis was performed using an isobar model. The model included a coherent mixture of six partial waves to describe all mass distributions, angular distributions, and the polarization of the $\ensuremath{\Lambda}$. The $\ensuremath{\Sigma}(1385)\ensuremath{\pi}$ decay mode was found to dominate the $\ensuremath{\Lambda}{\ensuremath{\pi}}^{+}{\ensuremath{\pi}}^{\ensuremath{-}}$ decay of the $\ensuremath{\Lambda}(1520)$, in disagreement with the results of a production reaction study of the same decay. The width for the decay was measured to be 1.40 \ifmmode\pm\else\textpm\fi{} 0.26 MeV. Mixing between the $\ensuremath{\Lambda}(1520)$ and the $\ensuremath{\Lambda}(1690)$ has been used in the past to describe the ${J}^{P}={\frac{3}{2}}^{\ensuremath{-}}$ baryons as SU(3) singlet and octet. Combining our rate for $\ensuremath{\Lambda}(1520)$ with a recently measured rate for $\ensuremath{\Lambda}(1690)\ensuremath{\rightarrow}\ensuremath{\Sigma}(1385)\ensuremath{\pi}$, we calculate the mixing angle $|\ensuremath{\theta}|=63\ifmmode^\circ\else\textdegree\fi{} \mathrm{to} 83\ifmmode^\circ\else\textdegree\fi{}$. This is in strong disagreement with the mixing angle derived from the two-body $D$-wave decays of the singlet and octet of -25 \ifmmode\pm\else\textpm\fi{} 6\ifmmode^\circ\else\textdegree\fi{}. Thus, some modification of the usual SU(3) description of these states needs to be made.

A high speed computer program for the kinematical analysis of bubble chamber events is described. The program treats individual particle interaction or decay vertices, subjecting the measured variables to the equations of energy and momentum according to the least‐squares criterion. This is done in four different cases in which the problem is overdetermined, and a fifth case is calculated in which the problem is just determined. The adjusted or computed variables corresponding to each particle are obtained in all cases as well as the first‐order error matrices for each type of variable. A connected chain of vertices may be processed in sequence.

The character of the ππ s-wave scattering amplitude near 980 MeV is determined from the reactions π + p→‡ ++ π + π − and ‡ ++ K + K − at 7GeV/c.

We present data on the inclusive distributions π + p → π ± + anything and π − p → π − + anything at momenta from 3.7 to 18.5 GeV/ c . Distributions are presented in the laboratory, center-of-mass and projectile systems, and the approach to scaling is discussed.

The A 2 mass spectrum is studied in the reaction π + p→A 2 + p atZZ 7 GeV/ c in a hydrogen bubble chamber in order to investigate previously reported structure. We report on 1400 A 2 events with mass resolutions of 3.8, 6.7 and 9.2 MeV in the K + K 0 , 3π and ηπ + channels.

We report the final results of a study of the time distribution of decays of neutral $K$ mesons produced in the reaction ${K}^{\ensuremath{-}}+p\ensuremath{\rightarrow}{\overline{K}}^{0}+n$. We present independent results based on 81 electronic and 38 muonic decays. Combining these with 133 ambiguous events, we find for the $\ensuremath{\Delta}S=\ensuremath{-}\ensuremath{\Delta}Q$ parameter $x$ the value $\mathrm{Re}(x)={{0.25}_{\ensuremath{-}0.09}}^{+0.07}$, $\mathrm{Im}(x)=0.00\ifmmode\pm\else\textpm\fi{}0.08$. This value lies about 2.5 standard deviations away from the point $x=0$, and to this extent our experiment suggests a violation of the $\ensuremath{\Delta}S=\ensuremath{\Delta}Q$ rule. In the course of an investigation of background processes, we identify and measure the rate of the radiative decay ${K}_{S}\ensuremath{\rightarrow}{\ensuremath{\pi}}^{+}{\ensuremath{\pi}}^{\ensuremath{-}}\ensuremath{\gamma}$.

Author(s): Crawford, Frank S.; Cresti, Marcello; Good, Myron L.; Gottstein, Klaus.; Lyman, Ernest M.; Solmitz, Frank T.; Stevenson, M. Lynn; Ticho, Harold.

Author(s): Crawford, Frank S.; Cresti, Marcello; Good, Myron L.; Solmitz, Frank T.; Stevenson, M.Lynn.

Author(s): Berge, J. Peter; Eberhard, Philippe; Hubbard, J. Richard; Merrill, Deane W.; Shafer, Janice B.; Solmitz, Prank T.; Stevenson, M. Lynn.

The Kππ enhancement at 1780 MeV (the "L meson") is copiously produced in our K+p experiment at 12 GeV/c. We show that this "meson" can be explained as a threshold enhancement in the KN(1420)π system. We see no evidence for this enhancement in channels other than KN(1420)π. © 1969 The American Physical Society.

Six cases of DELTA hyperons interacting with protons in a liquid hydrogen bubble chamber were found. The classes of DELTA interactions were DELTA + p yields DELTA + p (4 events) and DELTA + p yields SIGMA /sup +/ + n (2 events). No examples of the DELTA + p yields delta /sup 0/ + p reaction were found. The cross sections are computed for the reactions and for the inverse reactions. (W.D.M.)

Using the chsrge exchange of K- in a hydrogen bubble chamber, it was found that K/sup 0/ is 3.7 plus or minus 0.7 Mev heavier than K-. The incident K- ranged in energy from 10 to 150 Mev. A total of 41 charge-exchange events was observed. (W. D. M.)

The decay of the ${{Y}_{0}}^{*}(1520)\ensuremath{\rightarrow}\ensuremath{\Lambda}+\ensuremath{\gamma}$ has been discovered in the reaction ${K}^{\ensuremath{-}}+p\ensuremath{\rightarrow}\ensuremath{\Lambda}+\mathrm{neutrals}$. The angular distribution and polarization of the $\ensuremath{\Lambda}$ are consistent with a pure electric dipole transition. The cross section yields a partial width for the decay of 0.15\ifmmode\pm\else\textpm\fi{}0.03 MeV.

Several events have been observed in neutrino interactions which have an e+ and a K°s decay in the final state along with the conventional μ−. A discussion of their detection and relation to dimuon events will be presented. The significance of the associated strange particles and related kinematic quantities will be discussed.

Since its invention by Glaser in 1953, the bubble chamber has become a most valuable tool in high-energy physics. It combines a number of advantages of various older methods of particle detection: it offers high spatial resolution, rapid accumulation of data, some time resolution, and some choice of the nucleus whose interaction one wants to study (bubble chambers have been made to operate with a large number of different liquids, including H{sub 2}, D{sub 2}, He, Xe, and several hydrocarbons). In order to exploit the advantages of spatial resolution and rapid data accumulation, high-speed high-precision analysis procedures must be developed. In this article they discuss some of the problems posed by such analysis. The discussion is based largely on experience gained in performing hydrogen bubble chamber experiments with the University of California's Bevatron (6-Bev proton synchrotron).

Au event was found in the film taken in the course of atically seperated K- beam was passed into the Berkeley 15-inch hydrogen bubble chamber which was interpreted to be a beta decay of a lambda hyperon. It was consluded that a LAMBDA produced by the K/sup -/ decayed via the process ation for is given. (W.D.M.)

CONTENTS INTRODUCTION. . • . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. 375 1. REVIEW OF PROPERTIES OF SOME DISTRIBUTIONS. . . . . . . . . . . . . . . . . . . . . . .. 376 1.1 General remarks and definitions 376 1.2 Mean, moments. . . . .. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. 378 1.3 Multinomial and Poisson distributions.. . . . . . . . . . . . . . . . . . . . . . . . . . . .. 380 1.4 Normal and x2 distributions. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. 381 2 . ESTIMATION OF PARAMETERS 383 2.1 Bayesian approach. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. 384 2.2 Anti-Bayesian approach point estimation . . 387 2.3 Confidence intervals. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. 389 3. METHOD OF LEAST SQUARES. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 390 3.1 Linear problem .. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. 390 3.2 Polynomial fit...... . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. 392 3.3 Optimum properties. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. 393 3.4 Nonlinear problem . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. 393 3.5 Lagrange multipliers. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 394 4. ANALYSIS OF ANGULAR DISTRIBUTIONS. . 396 4.1 Single-parameter case. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. 396 4.2 General case. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. 399 4 .3 Histogram method. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 400 4.4 Detection efficiency. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. 401

In the course of a recent experiment involving the stopping of negative K mesons in a 10-inch liquid hydrogen bubble chamber, an interesting new reaction was observed to take place. The chamber is traversed by many more negative {mu} mesons than K mesons, so that in the last 75,000 photographs, approximately 2500 {mu}{sup -} decays at rest have been observed. In the same pictures, several hundred {pi}{sup -} mesons have been observed to disappear at rest, presumably by one of the ''Panofsky reactions''. For tracks longer than 10 cm, it is possible to distinguish a stopping {mu} meson from a stopping {pi} meson by comparing its curved path (in a field of 11,000 gauss) with that of a calculated template. In addition to the normal {pi}{sup -} and {mu}{sup -} stoppings, we have observed 15 cases in which what appears (from curvature measurement) to be a {mu}{sup -} meson comes to rest in the hydrogen, and then gives rise to a secondary negative particle of 1.7 cm range, which in turn decays by emitting an electron. (A 4.1-Mev {mu} meson from {pi} - {mu} decay has a range of 1.0 cm.) The energy spectrum of the electrons from these 15more » secondary particles looks remarkably like that of the {mu} meson. There are four electrons in the energy range 50 to 55 Mev, and none higher; the other electrons have energies varying from 50 Mev to 13 Mev. The most convincing proof that the primary particle actually comes to rest, and does not--for example--have a large resonant cross section for scattering at a residual range of 1.7 cm, is the following: In five of the 15 special events, there is a large gap between the last bubble of the primary track and the first bubble of the secondary track. This gap is a real effect, and not merely a statistical fluctuation in the spacing of the bubbles, since in some cases the tracks form a letter X, and in another case the secondary track is parallel to the primary, but displaced transversely by about 1 mm at the end of the primary. These real gaps appear also (although perhaps less frequently) between some otherwise normal-looking {mu}{sup -} endings and the subsequent decay electron; they are thought to be the distance traveled by the small neutral mesic atom.« less

As part of a continuing study of 8000 K absorptions in hydrogen. approximately 2000 SIGMA decays were examined for evidence of leptonic modes. The search for leptonic decay inodes was carried out by studying the momentum distribution of the SIGMA /sup -/ decay products. Of the total sample. 75O SIGMA /sup -/ and 250 SIGMA /sup +/ yields pi /sup +/ + n satisfied the lengt h of path criteria. (W.D.M.)

Angular distributions in SIGMA /sup +/ decay are analyzed for informatlon on SIGMA spin and parity conservation in SIGMA production. No evidence for a SIGMA spin > 1/2 or parity nonconservation in SIGMA prodiction is found. (auth)