Crystal Ball Detector Research Articles

Multiprocessor data acquisition system for high event rates at the Heidelberg/Darmstadt crystal ball

The Heidelberg/Darmstadt crystal ball detector uses a distributed data acquisition system consisting of a FASTBUS/CAMAC front-end, the Heidelberg Polyp multiprocessor system with thirty processor modules, and an online VAX. For this heterogeneous multicomputer system a distributed real-time operating system, which allows for even rates up to 2*10/sup 4/ events/s, was developed. It is managed user-transparently and fault-tolerantly. An overview of the system is given. The operating system is discussed, covering its general organization, event management, and control and communication. The data acquisition software is described.< <ETX xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">&gt;</ETX>

The Michel parameter for the decay τ→eν [formula omitted

The Crystal Ball detector at the Doris II storage ring at DESY has been used to study the electron energy spectrum of the decay τ→evv̄. In the standard model the Lorentz structure of the decay matrix element is of the well known V-A type, resulting in a Michel parameter of p=0.75. Our spectrum is found to be consistent with this value. A fit yields the value of 0.64±0.07.

Search for exotic tau decays

The Crystal Ball detector at the Doris II storage ring at DESY was used to search for the exotic decay processes τ→e γ, τ→e π 0, and τ→e η. No signal was observed. We obtained the following 90% CL upper limits on the branching fractions: B( τ→e γ)<2.0×10 −4, B( τ→e π 0)<1.4×10 −4, B( τ→e η)<2.4×10 −4.

Formation of the pseudoscalars pi 0, eta, and eta ' in the reaction gamma gamma --> gamma gamma.

The Crystal Ball detector has been used at the DORIS II storage ring at DESY to study the reaction e+e−→e+e−γ*γ*→e+e−γγ, where X is a narrow resonance with mass between 100 and 3000 MeV. Formation of π0, η, and η’ mesons is observed, and the following meson partial widths are obtained: Γπ0Γ0→γγ=7.7±0.5±0.5 eV, Γη−γγ=0.514±0.017±0.035 keV, and Γη’→γγ=4.7±0.5±0.5 keV. No other narrow resonances are observed, and upper limits are given for the product ΓX→γγBX→γγ. .AE

Crystal Ball Results on Tau Decaysa

This report reviews measurements and upper limit determinations for a number of exclusive 1-prong tau decay modes using the Crystal Ball detector. These results are important input to the apparent discrepancy between the topological and sum-of-exclusive branching fractions in 1-prong tau decays.

Determination of Γ ee of the ϒ(1 S) and ϒ(2 S) resonances, and measurement of R at W = 9.46 GeV

Using the Crystal Ball detector operating at the DORIS II storage ring we have measured the leptonic partial widths Γ ee of the ϒ(1 S) and ϒ(2 S) resonances. We discuss a consistent definition of Γ ee and show the effect on it by applying different prescriptions for radiative corrections. We also give a value of R, the ratio of non-resonant hadronic cross section to the Born cross section of μ pair production, at a c.m. energy of W = 9.46 GeV. All numerical results are preliminary.

Experimental upper limits for the hadronic transitions Υ(2S)→ηΥ(1S) and Υ(2S)→π0Υ(1S)

Using the Crystal Ball detector at thee +e− storage ring DORIS-II, we have searched for the hadronic transitions Υ(2S)→ηΥ(1S) and Υ(2S)→π0Υ(1S) in exclusive decays where the Υ(1S) decays into ane +e− or aµ + µ - pair and the η and π0 are detected by their decay modes η→γγ, η→γγ and π0→γγ. From the number of observed events we derive, after consideration of possible background sources, upper limits on the branching ratiosB(Υ(2S)→ηΥ(1S))<0.7% andB(Υ(2S)→π0Υ(1S))<0.8% at the 90% confidence level.

Chi b states in exclusive radiative decay of the Upsilon (2S).

The Crystal Ball detector at the DESY storage ring DORIS II has been used to study radiative decays of the \ensuremath{\Upsilon}(2S) resonance. We report on the analysis of the exclusive channel \ensuremath{\Upsilon}(2S)\ensuremath{\rightarrow}\ensuremath{\gamma}${\ensuremath{\chi}}_{b}$, ${\ensuremath{\chi}}_{b}$\ensuremath{\rightarrow}\ensuremath{\gamma}\ensuremath{\Upsilon}(1S)\ensuremath{\rightarrow}${e}^{+}$${e}^{\mathrm{\ensuremath{-}}}$ or ${\ensuremath{\mu}}^{+}$${\ensuremath{\mu}}^{\mathrm{\ensuremath{-}}}$. We detect two ${\ensuremath{\chi}}_{b}$ states by observing two monochromatic photon lines at energies (107.0\ifmmode\pm\else\textpm\fi{}1.1\ifmmode\pm\else\textpm\fi{}1.3) MeV and (131.7\ifmmode\pm\else\textpm\fi{}0.9\ifmmode\pm\else\textpm\fi{}1.3) MeV, respectively. The product branching ratios B[\ensuremath{\Upsilon}(2S)\ensuremath{\rightarrow}\ensuremath{\gamma}${\ensuremath{\chi}}_{b}$]\ifmmode\times\else\texttimes\fi{}B[${\ensuremath{\chi}}_{b}$\ensuremath{\rightarrow}\ensuremath{\gamma}\ensuremath{\Upsilon}(1S) ] are (1.6\ifmmode\pm\else\textpm\fi{}0.3\ifmmode\pm\else\textpm\fi{}0.2)% for the first state and (2.1\ifmmode\pm\else\textpm\fi{}0.3\ifmmode\pm\else\textpm\fi{}0.3)% for the second. For the product branching ratio of the third ${\ensuremath{\chi}}_{b}$ state, which has been observed in inclusive measurements, we find an upper limit of 0.2% (90% C.L.). Combining our results with inclusive measurements, branching ratios for ${\ensuremath{\chi}}_{b}$\ensuremath{\rightarrow}\ensuremath{\gamma}\ensuremath{\Upsilon}(1S) are derived. Using theoretical estimates for the radiative widths of the ${\ensuremath{\chi}}_{b}$ states, we determine their hadronic widths; the results are compared with QCD predictions.

Formation of delta(980) and A2(1320) in photon-photon collisions.

The reaction γγ→π0η has been investigated with the Crystal Ball detector at the DESY storage ring DORIS II. Formation of δ(980) and A2(1320) has been observed with γγ partial widths Γγγ(A2)=1.14±0.20±0.2 6 keV and Γγγ(δ)B(δ→πη)=0.19±0.07 −0.07+0.10 keV.

Correlated spin orientations in 12C

The correlation between the spin orientations of the two $^{12}\mathrm{C}$(${2}^{+}$) nuclei in mutual inelastic $^{12}\mathrm{C}$ + $^{12}\mathrm{C}$ scattering has been deduced from the directional correlations of the particle-coincident $\ensuremath{\gamma}$ rays measured with a crystal-ball detector. Resonances in the cross section are found to be nearly uniquely associated with the mutually aligned component. The strong resonance structure as well as the characteristic behavior of the angular distributions of this reaction component are suggestive of the formation of a rotating dinuclear complex in the sticking configuration.

Observation of three P states in the radiative decay of Upsilon (2S).

The inclusive photon spectrum in hadronic decays of the UPSILON(2S) is measured with the Crystal Ball detector at DORIS II. Four well separated photon lines, which are consistent with the decay hypothesis UPSILON(2S)..--> gamma..+ /sup 3/P/sub 2,1,0/ and /sup 3/P/sub 2,1/..--> gamma..+UPSILON(1S), are observed. The energies of the lines from the primary transitions are E/sub gamma1/ = 110.4 +- 0.8 +- 2.2 MeV, E/sub gamma2/ = 130.6 +- 0.8 +- 2.4 MeV and E/sub gamma3/ = 163.8 +- 1.6 +- 2.7 MeV; the branching fractions are (5.8 +- 0.7 +- 1.0)%, (6.5 +- 0.7 +- 1.2)%, and (3.6 +- 0.8 +- 0.9)%, respectively. The secondary transitions center at approx. =430 MeV with a combined branching fraction of (3.6 +- 0.7 +- 0.5)%.

Has the Higgs boson been seen in the Crystal Ball?

From the Crystal Ball detector at the DORIS electron–positron collider in Hamburg comes strong evidence of an 8.3-GeV particle for which there appears to be no prosaic explanation. “If it's real, it has to be very important,” says Gordon Kane (University of Michigan), expressing the widespread excitement that this new state has generated among high-energy theorists.

Physics with the Crystal Ball Detector

Following a major shortage of 99Mo in the 2009–2010 period, concern grew that the aging reactor production facilities needed to be replaced. Most producers were using highly enriched 235U (HEU) as the target material. The Organisation for Economic Co-...Read More

Study of the reactionψ′→γγJψ

The Crystal Ball detector at SPEAR has been used to investigate the decays ψ′→γγJψ, Jψ→(e+e− or μ+μ−) resulting from production of 8×105ψ′. From this selection of the data we measure the branching ratios for the processes ψ′→(η or π0)Jψ and ψ′→γχ, χ→γJψ. An analysis of the angular correlations in the latter process furnishes measurements of the χ(3.55) and χ(3.51) spins and of the multipole structure of the radiative transitions.Received 9 December 1981DOI:https://doi.org/10.1103/PhysRevD.25.2259©1982 American Physical Society

Upper Limit forJΨ→γ +Axion

A search has been made with the Crystal Ball Detector for axionlike particles in radiative JΨ decays. An upper limit on the branching ratio B(JΨ→γ+a)<1.4×10−5 (90% C.L.) is obtained. This result holds for long-lived, noninteracting pseudoscalar or vector particles of mass less than 1 GeV. Thus, this experiment also places stringent limits on the existence of other possible light bosons such as those arising in supersymmetric theories.Received 8 February 1982DOI:https://doi.org/10.1103/PhysRevLett.48.903©1982 American Physical Society

Measurement of InclusiveηProduction ine+e−Interactions near Charm Threshold

We have measured the inclusive cross section for eta production in e/sup +/e/sup -/ interactions near charm threshold using the Crystal Ball detector. No pronounced structure in the energy dependence is observed. By comparing cross sections above and below charm threshold we obtain the limits (90% confidence limit): R(e/sup +/e/sup -/..-->..FF-barX)Br(F..-->..etax) ..etax)<0.13 (averaged over charged and neutral D components of the psi''(3770) decays). Our results are inconsistent with a previous report of a large energy dependence of the eta cross section ascribed to the crossing the FF* and F*F* production thresholds.

Measurement of the Decaysψ′→ηJψandψ′→π0Jψ

The Crystal Ball detector at SPEAR has been used to investigate the decays psi'..-->..etaJ/psi and psi'..--> pi../sup 0/J/psi resulting from production of 776 000 psi'. Our measurement for the branching ratio of the eta mode is (2.18 +- 0.14 +- 0.35)%, where the first error results from statistics and acceptance uncertainties, and the second error is systematic; this is almost a factor of 2 smaller than found in early experiments. For the isospin-nonconserving ..pi../sup 0/ mode, a branching ratio (0.09 +- 0.02 +- 0.01)% is obtained.

The plastic ball - a multi-detector, large solid angle spectrometer with charged particle identification for the bevalac

For the study of central relativistic nuclear heavy ion collisions, which are characterized by the emission of a large number of particles, one needs a detector which covers a large solid angle - 4π if possible - and which is capable of identifying charged particles. The high multiplicity requires a large number of detectors, and the need for charged-particle identification requires a measurement of the energy loss, and the total energy for each particle detected. The spectrometer consists of 815 detector modules, which cover 94% of 4π. The geometry of these modules has been taken from the Stanford crystal ball detector for γ-rays - with minor modifications. This geometry is suited for the high multiplicities of particles emitted in relativistic heavy ion collisions. The dimension of the individual elements have been chosen to stop 240 MeV protons. Above this energy reaction losses start to dominate, so that the light output of a scintillator would no longer be a true indication of the energy. Out of 100 charged particles, 94 will hit the Plastic Ball, 87 will fire a detector element, and 80 will be identified uniquely. For the individual detector modules we have used the "Phoswich" idea, by gluing a 4 mm thick CaF <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> scintillator to a 35 cm thick plastic scintillator (NE114) with the shape of a truncated pyramid, which is viewed by one photomultiplier tube (PM2202B).The extremely different decay times of the CaF <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> scintillator and the plastic allow us to separate their light output by integrating the signal from the phototube for the first 20 nsec (the "E signal") and then integrating the "delayed" signal for 2 μsec (the "ΔE signal"). This constitutes a simple low cost detector telescope, which can identify the hydrogen and helium isotopes. We describe the electronic setup to separate the "ΔE" and "E" signals, and give some test results, which show the separation and identification, of protons, deuterons, tritons, <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">3</sup> He, and alpha particles.

Compact Multiwire Proportional Chambers and Electronics for the Crystal Ball Detector

A double gap of cylindrical proportional chambers has been designed and built for use with a large solid angle, modular NaI(Tl) array (The Crystal Ball). The chambers are constructed of three coaxial foam-epoxy shells, covered with an aluminum-mylar laminate. One of the high voltage cathodes in each chamber has been photo-etched to produce a pattern of stripes and precise position measurements of tracks passing transverse to the chamber axis are found by pulse height analyzing the shaped and amplified induced strip signals. Performance of the chamber using both the strip signals and the sense wire readout is presented. The design of both the signal handling electronics and the digital portions of the systems is discussed.