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The disappearance of reactor $$\bar{\nu }_e$$ ν ¯ e observed by the Daya Bay experiment is examined in the framework of a model in which the neutrino is described by a wave packet with a relative intrinsic momentum dispersion $$\sigma _\mathrm{{rel}}$$ σ rel . Three pairs of nuclear reactors and eight antineutrino detectors, each with good energy resolution, distributed among three experimental halls, supply a high-statistics sample of $$\bar{\nu }_e$$ ν ¯ e acquired at nine different baselines. This provides a unique platform to test the effects which arise from the wave packet treatment of neutrino oscillation. The modified survival probability formula was used to fit Daya Bay data, providing the first experimental limits: $$2.38 \times 10^{-17}< \sigma _\mathrm{{rel}} < 0.23$$ 2.38 × 10 - 17 < σ rel < 0.23 . Treating the dimensions of the reactor cores and detectors as constraints, the limits are improved: $$10^{-14} \lesssim \sigma _\text {rel} < 0.23$$ 10 - 14 ≲ σ rel < 0.23 , and an upper limit of $$\sigma _\text {rel}

We describe here the characteristic features of the ringing we observed following large PMT signals in the Daya Bay reactor antineutrino experiment. We conclude that the ceramic capacitors used in the circuitry of the PMT bases and the HV-signal decouplers are the primary cause for this ringing. We present some possible schemes to reduce the ringing when replacing these ceramic capacitors is not feasible.

I present here a brief description of the goals, method and status of the Daya Bay antineutrino oscillation experiment to measure the mixing angle Θ 13 .

In the Daya Bay Reactor Neutrino Experiment 960 20-cm-diameter waterproof photomultiplier tubes are used to instrument three water pools as Cherenkov detectors for detecting cosmic-ray muons. Of these 960 photomultiplier tubes, 341 are recycled from the MACRO experiment. A systematic program was undertaken to refurbish them as waterproof assemblies. In the context of passing the water leakage check, a success rate better than 97% was achieved. Details of the design, fabrication, testing, operation, and performance of these waterproofed photomultiplier-tube assemblies are presented., Comment: 16 pages, 11 figures. Submitted to Nucl. Instr. Meth

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Beam polarization at e+-e− linear colliders will be a powerful tool for high precision analyses. Often it is assumed that the full information from polarization effects is provided by polarization of the electron beam and no further information can be obtained by the simultaneous polarization of the positrons. In this paper we point out the advantages of polarizing both beams, and summarize the polarization-related results of the Higgs, Electroweak, QCD, SUSY and Alternative Theories working groups of the ECFA/DESY workshop for a planned linear collider operating in the energy range √s = 500-800 GeV.

The Daya Bay reactor antineutrino experiment is designed to make a precision measurement of the neutrino mixing angle theta13, and recently made the definitive discovery of its nonzero value. It utilizes a set of eight, functionally identical antineutrino detectors to measure the reactor flux and spectrum at baselines of 300 - 2000m from the Daya Bay and Ling Ao Nuclear Power Plants. The Daya Bay antineutrino detectors were built in an above-ground facility and deployed side-by-side at three underground experimental sites near and far from the nuclear reactors. This configuration allows the experiment to make a precision measurement of reactor antineutrino disappearance over km-long baselines and reduces relative systematic uncertainties between detectors and nuclear reactors. This paper describes the assembly and installation of the Daya Bay antineutrino detectors., 31 pages, 19 figures

Antiproton-production and nucleon-interaction cross sections were investigated for antiprotons in the energy range 0.5 to 1.0 BeV. The antiprotons were distinguished from other particles produced at the Bevatron by a system of scintillation and velocity-selecting-\ifmmode \check{C}\else \v{C}\fi{}erenkov counters. The excitation function and momentum distribution were recorded for antiproton production in carbon and compared with statistical model expectations.The antiprotons were directed by a system of bending and focusing magnets to a liquid hydrogen target. An array of plastic scintillation counters, which almost completely surrounded the hydrogen target, was used to determine the $\overline{p}\ensuremath{-}p$ total, elastic, inelastic, and charge-exchange cross sections. Near 500 MeV the total $\overline{p}\ensuremath{-}p$ cross section is about 120 mb, and it slowly decreases to 100 mb near 1 BeV. The inelastic cross section, which is principally due to the annihilation process, represents nearly $\frac{2}{3}$ of the total cross section. The elastic-scattering distribution is highly peaked in the forward direction and can be fitted by an optical model.The total and partial cross sections were also determined for the collisions of antiprotons with deuterons. The $\overline{p}\ensuremath{-}d$ total and inelastic cross sections were found to be approximately 1.8 times the $\overline{p}\ensuremath{-}p$ cross sections. Corrections were made for the shielding of nucleons within the deuteron in order to ascertain the $\overline{p}\ensuremath{-}n$ interaction. The results indicate that the $\overline{p}\ensuremath{-}p$ and $\overline{p}\ensuremath{-}n$ cross sections are very nearly equal in this energy region, and that they satisfy the inequalities required by charge independence.

The polarimeters needed to monitor and measure electron beam polarization at the Stanford Linear Collider are discussed. Two types of polarimeters, are to be used. The first is based on the spin dependent elastic scattering of photons from high energy electrons. The second utilizes the spin dependence of elastic electron-electron scattering. The plans of the SLC polarization group to measure and monitor electron beam polarization are discussed. A brief discussion of the physics and the demands it imposes on beam polarization measurements is presented. The Compton polarimeter and the essential characteristics of two Moeller polarimeters are presented. (LEW)

Cross sections for negative pion production in 183-MeV/nucleon Ne+NaF and Ne+Pb collisions have been measured at laboratory angles from 20/sup 0/ to 90/sup 0/. Almost isotropic angular distributions in the nucleon-nucleon c.m. frame are observed. The energy spectra in this frame are of an exponential type with an inverse slope of 25 MeV for NaF and 26 MeV for Pb. No evidence of a bump predicted to result from pionic instability is observed. Possible mechanisms for producing high-energy pions are discussed.

Author(s): Dieterle, Byron D.; Arens, John F.; Chamberlain, Owen; Grannis, Paul D.; Hansroul, Michel J.; Holloway, Leland E.; Johnson, Claiborne H.; Schultz, Claude H.; Steiner, Herbert M.; Shapiro, Gilbert; Weldon, David M.

The cross sections and proton polarizations in pi +-p interactions st 310 Mev are measured, in an attempt to find an unambiguous set of SP, SPD, or SPDF phase shifts for the system. The experimental data can be made to fit unambiguously a given set of SPD phase shifts. The data cannot he fitted adequately by a set of SP shifts alone, and the data are fitted ambiguously by several sets of SPDF shifts. (T. F.H.)

We have measured the total fission cross sections of ${\mathrm{U}}^{238}$, ${\mathrm{U}}^{235}$, ${\mathrm{Th}}^{232}$, ${\mathrm{Bi}}^{209}$, and ${\mathrm{Au}}^{197}$ for high-energy protons. A cancellation-type ionization chamber was used to detect the fission fragments. The observed fission cross sections are compared to the total inelastic cross sections in order to obtain the relative fission probability as a function of proton energy.

The recoil-proton polarization in {pi}{sup +}-p elastic scattering at 310-Mev incident-pion laboratory kinetic energy has been experimentally measured at four scattering angles with scintillation counters. Polarization values obtained, related rms experimental errors, and mean center-of-mass recoil angles are: +0.044 {+-} 0.062 at 114.2 deg. =0.164 {+-} 0.057 at 124.5 deg, -0.155 {+-} 0.044 at 133.8 deg, and -0.162 {+-} 0.037 at 145.2 deg. The sign of the polarization is defined to be positive when a preponderance of the recoil protons had their spin vectors pointing in the direction of {rvec P}{sub i} x {rvec p}{sub f}, where this quantity is the cross product of the initial and final momentum vectors of the conjugate pions. A beam of 1 x 10{sup 6} pions per sec incident upon a 1.0-g/cm{sup 2}-thick liquid-hydrogen target produced the recoil protons, which were then scattered by a carbon target at a mean energy varying with recoil angle from 113 to 141 Mev. The polarization of the recoil protons was analyzed by measuring the asymmetry produced in the carbon scattering. A proton beam of known polarization was used to determine the analyzing ability (measured asymmetry divided by the polarization of the incident protons) of the system atmore » each recoil angle. Values obtained for the analyzing ability range from 0.41 to 0.57.« less

About 500 antiprotons in a partially purified antiproton beam have been observed to enter the 30-in. propane bubble chamber. An arrangement of counters identified the antiproton events, thus reducing scanning to a minimum and also providing a sample of antiprotons free of scanning bias. The antiprotons entered the propane at a kinetic energy of 220 Mev and were brought to rest. Scattering and annihilation interactions in both hydrogen and carbon have been observed as a function of antiproton energy. Differential scattering cross sections have been obtained, and the following total cross sections have been measured for antiproton kinetic energies, $T$, in the ranges 75 to 137.5 Mev and 137.5 to 200 Mev: The above results show satisfactory agreement with the Ball-Chew theory where comparison can be made.

Using the 1.19-Bev/c antiproton beam recently discovered at the Berkeley Bevatron of the University of California, we have measured the attenuation cross section in beryllium and copper. These cross sections are compared to attenuation measurements made with the same geometry using positive protons of the same incident energy (497 Mev). The measurements were made at cut-off angles ${\ensuremath{\theta}}_{c}$ of 12.7\ifmmode^\circ\else\textdegree\fi{} for copper, and at 18\ifmmode^\circ\else\textdegree\fi{} for beryllium. For both copper and beryllium the measured attenuation cross section for antiprotons is twice that for positive protons, with a statistical error of \ifmmode\pm\else\textpm\fi{}15%. In addition, for both elements, more than half the attenuation events resulted in one or more fast charged secondary particles ($\ensuremath{\beta}g~0.75$) --- probably indicating that annihilations had taken place.The cross section results are: for copper at ${\ensuremath{\theta}}_{c}=12.7\ifmmode^\circ\else\textdegree\fi{}$, ${\ensuremath{\sigma}}_{p}^{\ensuremath{-}}=1.58\ifmmode\pm\else\textpm\fi{}0.22$, ${{\ensuremath{\sigma}}_{p}}^{+}=0.780\ifmmode\pm\else\textpm\fi{}0.069$; and for beryllium at ${\ensuremath{\theta}}_{c}=18\ifmmode^\circ\else\textdegree\fi{}$, ${\ensuremath{\sigma}}_{p}^{\ensuremath{-}}=0.365\ifmmode\pm\else\textpm\fi{}0.059$, ${{\ensuremath{\sigma}}_{p}}^{+}=0.178\ifmmode\pm\else\textpm\fi{}0.013$, where the units are ${10}^{\ensuremath{-}24}$ ${\mathrm{cm}}^{2}$. For copper and beryllium, respectively, the average energies in the absorbers were 430 and 455 Mev.

At the 184-inch synchrocyclotron in Berkeley, data were obtained on elastic pi /sup +/-scattering at 310 Mev. Quantities measured were the differential cross section, the total cross section, and the polarization of the recoil protons as a function of center-of-mass angle. The data were analyzed in terms of S, P, and D waves and only one acceptable solution was obtained--the Fermi type phase shift. Errors on the small phase shift were reduced to less than 1 deg . (B.O.G.)

Using a polarized proton target, we have measured the polarization parameter P({theta}) in pion-proton scattering for both positive and negative pions. Because there seems to be a great deal of current interest in the analysis of pion-proton scattering we wish to present these experimental results at this time even though we have not yet completed their analysis. The measurement consisted of scattering pions from polarized target protons and observing the asymmetry in scattered intensity, I({theta}), as the target protons spin directions were reversed. The intensity for scattering from a target of polarization P{sub T} is I({theta}){sub pol.} = I({theta}){sub unpol.} (1 + P({theta})P{sub T}), where the parameter P({theta}) is the same as the recoil proton polarization in scattering pions from unpolarized protons under the assumption that parity is conserved in the process.

Experiments are described that have been designed to measure separately annihilation and reaction cross sections for antiprotons of approximately 450 MeV on oxygen, copper, silver, and lead. A new and more luminous spectrograph has been built for this experiment. The antiproton cross sections a r e compared with total proton cross sections, and are found to be larger by a factor varying from 1.74 for oxygen to 1.39 for silver. Calculations based on the optical model give a reasonable connection between these cross sections and the 6-p and 6-n cross sections. Finally, the information available on antiproton production cross sections is collected. There are indications that a free nucleon is several times as effective as a bound one for producing antiprotons.

A comprehensive phase-shift analysis of ${\ensuremath{\pi}}^{+}\ensuremath{-}p$ elastic-scattering data at 310-Mev incident-pion laboratory kinetic energy has been performed. The experimental data utilized include measurements of the differential and total cross sections and of the recoil-proton polarization. The $D$-wave phase shifts were found to be definitely needed in order to attain an adequate fit to the data. A general search for phase-shift solutions was carried out, using $S$-, $P$-, and $D$-wave phase shifts. One solution\char22{}of the Fermi type\char22{}was found that fits the data significantly better than any of the other solutions obtained. The calculated errors in the phase shifts of this set vary from 0.4 to 0.6 deg. Because it was felt that these errors might be deceivingly restrictive, the effects of small nuclear $F$-wave phase shifts on the results of the analysis were investigated and were found to be large: not only are the uncertainties in the original Fermi-type solution increased, but additional sets of phase shifts arise that fit the data well. One of these new solutions is similar to the original Fermi set except that the magnitudes of the phase shifts in this new fit are in general larger than those in the initial solution, and the signs of the $D$-wave phase shifts are reversed. The nuclear phase shifts in the original Fermi solution and their rms errors are (when $F$-wave phase shifts are allowed): ${S}_{3,1}=\ensuremath{-}17.2\ifmmode\pm\else\textpm\fi{}2.6$ deg, ${P}_{3,1}=\ensuremath{-}2.9\ifmmode\pm\else\textpm\fi{}4.0$ deg, ${P}_{3,3}=135.0\ifmmode\pm\else\textpm\fi{}0.6$ deg, ${D}_{3,3}=3.1\ifmmode\pm\else\textpm\fi{}2.6$ deg, ${D}_{3,5}=\ensuremath{-}4.9\ifmmode\pm\else\textpm\fi{}2.1$ deg, ${F}_{3,5}=0.5\ifmmode\pm\else\textpm\fi{}0.6$ deg, ${F}_{3,7}=\ensuremath{-}0.6\ifmmode\pm\else\textpm\fi{}1.4$ deg. Although theory appears to favor this set, further theoretical and experimental evidence is desirable. The values given here for the first five phase shifts approximate the corresponding values obtained when the $F$-wave phase shifts were assumed negligible. However, all except ${P}_{3,3}$ fall outside the limits set by the small original errors. Inelastic-scattering processes were neglected during the phase-shift analysis. Calculations indicate that, if these processes could properly be taken into account, any changes in the quoted values of the phase shifts would probably be well within the corresponding errors given here. Extension of the phase-shift inquiries to include $G$ waves was attempted, but it was observed that the available data and theory do not allow the $G$-wave interaction to be significantly incorporated into the analysis.

The measurements yielded information on the antiproton-carbon scattering cross section for scattering; angles of 5 deg (lab) or more. A total of 70 antiprotoncarbon scattering events were seen in a total antiproton path length of 179 meters of liquid propane (density = 0.42 g/cm/sup 3/). The high ratio of the total antiproton cross section observed at higher energies on several elements also extends to the lower energies considered. (M.H.R.)

The relative importance of various mechanisms which may play a role in the production of backward energetic protons has been studied in 800 MeV proton-nucleus collisions. Energetic protons (P\ensuremath{\ge}350 MeV/c) at \ensuremath{\theta}=118\ifmmode^\circ\else\textdegree\fi{} were measured in coincidence with particles emitted in the angular range from 15\ifmmode^\circ\else\textdegree\fi{} to 100\ifmmode^\circ\else\textdegree\fi{}. Both in-plane (\ensuremath{\Delta}\ensuremath{\varphi}=180\ifmmode^\circ\else\textdegree\fi{}) and out-of-plane (\ensuremath{\Delta}\ensuremath{\varphi}=90\ifmmode^\circ\else\textdegree\fi{}) coincidences were measured. The data have been decomposed into several categories depending on the excitation energy of the residual nucleus. Momentum spectra, angular distributions, and target mass dependences of these categories have been studied. The scattering of the incident proton by a correlated nucleon cluster seems to play an important role. From the proton spectrum associated with the p-d quasi-elastic scatterings, the momentum spread of the pn system (``d'') inside the nucleus has been determined. The momentum spread of the ``d'' obtained by the p-d quasi-elastic scatterings is found to be smaller than the spread observed in heavy-ion projectile fragmentation into deuterons. From the mass dependence of the ratio of the p-d to p-p quasi-elastic scattering cross sections, the mean free path of deuterons inside the nucleus has been determined.

In the last five years there has been a sharp increase in activity, both experimental and theoretical, in the study of collisions between energetic nuclei. Here I would like to review briefly the present status of this field of research with particular emphasis on recent developments. Because of time limitations I will have to omit a number of relevant and interesting topics such as hadron-nucleus interactions at very high (20–400 GeV) energies. Fortunately there are several recent reviews on this subject1, 2, 3). In any case I would like to apologize in advance to all those who may feel slighted (or offended) by my remarks.

The polarization parameter in elastic {pi}{sup -}p scattering has been measured, at the Berkeley 184 synchrocyclotron,l with the use of a polarized proton target. At 318, 337 and 390 Mev incident pion kinetic energy, the angular range from 70{sup o} to 180{sup o} in the center of mass system was covered. At 229 Mev polarization measurements were made in the angular range 150{sup o} to 180{sup o}. Phase shift analyses using these and other published data were made at the two lowest energies.

A comprehensive phase-shift analysis of {pi}{sup +}-p elastic-scattering data at 310-Mev incident-pion laboratory kinetic energy has been performed. The experimental data utilized include measurements of the differential and total cross sections and of the recoil-proton polarization. The D-wave phase shifts were found to be definitely needed in order to attain an adequate fit to the data. A general search for phase-shift solutions was carried out, using S-, P-, and D-wave phase shifts. One solution--of the Fermi type--was found that fits the data significantly better than any of the other solutions obtained. The calculated errors in the phase shifts of this set vary from 0.4 to 0.6 deg. Because it was felt that these errors might be deceivingly restrictive, the effects of small nuclear F-wave phase shifts on the results of the analysis were investigated and were found to be large; not only are the uncertainties in the original Fermi-type solution increased, but additional sets of phase shifts arise that fit the data well. One of these new solutions is similar to the original Fermi set except that the magnitudes of the phase shifts in this new fit are in general larger than those in the initial solution, and the signsmore » of the D-wave phase shifts are reversed. The nuclear phase shifts in the original Fermi solution and their rms errors are (when F-wave phase shifts are allowed): S{sub 3,1} = -17.2 {+-} 2.6 deg, P{sub 3,1} = -2.9 {+-} 4.0 deg, P{sub 3,3} = 135.0 {+-} 0.6 deg, D{sub 3,3} = 3.1 {+-} 2.6 deg, D{sub 3,5} = -4.9 {+-} 2.1 deg, F{sub 3,5} = 0.5 {+-} 0.6 deg, F{sub 3,7} = -0.6 {+-} 1.4 deg. Although theory appears to favor this set, further theoretical and experimental evidence is desirable. The values given here for the first five phase shifts approximate the corresponding values obtained when the F-wave phase shifts were assumed negligible. However, all except P{sub 3,3} fall outside the limits set by the small original errors. Inelastic-scattering processes were neglected during the phase-shift analysis. Calculations indicate that, if these processes could properly be taken into account, any changes in the quoted values of the phase shifts would probably be well within the corresponding errors given here. Extension of the phase-shift inquiries to include G waves was attempted, but it was observed that the available data and theory do not allow the G-wave interaction to be significantly incorporated into the analysis.« less

Using the 1.19-Bev/c antiproton beam recently discovered at the Berkeley Bevatron of the University of California, we have measured the attenuation cross section in beryllium and copper. These cross sections are compared to attenuation measurements made with the same geometry using positive protons of the same incident energy (497 MeV).

Observation of antiprotons in a propane or hydrogen bubble chamber offers the possiblity of studying several phenomena for which counter or photographic emulsion techniques are less suitable. Because there is a high ratio of pions, muons, and electrons to antiprotons in the available momentum-analyzed beams, these beams cannot be used in the bubble chamber without an initial purification, which increases the ratio of antiprotons to other particles. Such a purification has been achieved by utilizing the difference in rates of momentum loss in absorbers between antiprotons and other particles. The principle of the method is to pass a momentum-analyzed beam through an absorber. Since particles of unequal mass do not have the same specific ionization they lose different amounts of momentum, and a further magnetic deflection suffices to separate the particles physically according to mass. In this experiment a desirable momentum for antiprotons entering the bubble chamber was 684 Mev/c; however, at this momentum the ratio of undesirable particles to antiprotons at the target where they are produced is about 6 x 10{sup 5}. By starting with 970-Mev/c particles at the target and using the method of differential absorption, they decreased the ratio of undesirable particles (87% {mu}{sup -}, 105more » {pi}{sup -}, 3% e{sup -}) to antiprotons entering the bubble chamber at 684 Mev/c to 1.5 x 10{sup 4}. A system of counters indicatd when an antiproton entered the bubble chamber, and although the chamber was expanded on every Bevatron pulse, the lights were flashed and the chamber photographed only when an antiproton entered.« less

tiCRL UNIVERSITY OF CALIFORNIA TWO-WEEK LOAN COpy This is a Library Circulating Copy wh ich may be borrowed for two weeks. For a personal retention copy, call Tech. Info. Diuision, Ext. 5545 BERKELEY, CALIFORNIA

Observation of antiproton--proton collisions in a propane bubble chamber at an average energy of 120 Mev has been accomplished. The ratio of antiprotons to other particles in the beam has been increased by utilizing the differential rate of momentum loss in absorbers between antiprotons and other particles. The angular distribution of 33 p-p scattering events between 15 and 165 deg c.m. is presented. (W.D.M.)

The surface chemistry of Cr2+ and Cr3+ in chromia–alumina catalyst is investigated. Electron spin resonance studies revealed considerable changes in the behaviour of the signals ascribed to Cr3+(at g= 1.986) when exposed to H2, C2H4 and water vapour at 373 K. This work, when combined with the results from adsorption studies, allows some speculation upon the mode of adsorption of the gaseous species on the chromium ions.