110466342
Performance and Aging Studies of BaBar Resistive Plate Chambers
The BaBar detector is currently operating nearly 200 Resistive Plate Chambers (RPCs), constructed as part of an upgrade of the forward endcap muon detector in 2002. Although the average RPC efficiency remains high, numerous changes in the RPC performance (increased currents and rates) have been observed. A few of the highest rate RPCs have suffered efficiency losses of more than 15%. Several types of efficiency loss have been observed. Tests with humidified gas have shown that some of the lost efficiency is recoverable. However, efficiency losses in the highest rate regions have not yet improved with humid gases.
108905088
A 32 channels charge integrating ADC based on digital signal integration
Abstract A digital charge integrator with programmable gate width and range has been designed for use in the KLOE drift chamber front-end chain. The system has a resolution of 9 bits ranging from 600 fC / count up to ≈ 76  pC and integration time ranging from 100 ns to about 13 μ s . Thirty-two channels have been packaged in a single VME 9U board.
109329842
Improved Particle Identification Using Cluster Counting in a Full-Length Drift Chamber Prototype
Single-cell prototype drift chambers were built at TRIUMF and tested with a ~210MeV/c beam of positrons, muons, and pions. A cluster-counting technique is implemented which improves the ability to distinguish muons and pions when combined with a traditional truncated-mean charge measurement. Several cluster-counting algorithms and equipment variations are tested, all showing significant improvement when combined with the traditional method. The results show that cluster counting is a feasible option for any particle physics experiment using drift chambers for particle identification. The technique does not require electronics with an overly high sampling rate. Optimal results are found with a signal smoothing time of ~5ns corresponding to a ~100MHz Nyquist frequency.
63620607
The new BaBar Analysis Model
As part of a general Computing Model upgrade, BaBar has deployed a new analysis model. The new analysis model was designed to overcome the major shortcomings of the previous analysis model. In particular, the new analysis model consolidates several redundant data formats, allows users to customize the data format for their analysis, and provides a wider range of data access options than the old model, while maintaining backwards compatibility with BaBar’s existing analysis interface and analysis code base. The new analysis model was used in roughly half the analyses submitted to the recent ICHEP 2004 conference, and has been enthusiastically welcomed by the BaBar analysis community.
52216370
Measuring propagation speed of Coulomb fields
The problem of gravity propagation has been subject of discussion for quite a long time: Newton, Laplace and, in relatively more modern times, Eddington pointed out that, if gravity propagated with finite velocity, planet motion around the sun would become unstable due to a torque originating from time lag of the gravitational interactions. Such an odd behavior can be found also in electromagnetism, when one computes the propagation of the electric fields generated by a set of uniformly moving charges. As a matter of fact the Liénard–Weichert retarded potential leads to the same formula as the one obtained assuming that the electric field propagate with infinite velocity. The Feynman explanation for this apparent paradox was based on the fact that uniform motions last indefinitely. To verify such an explanation, we performed an experiment to measure the time/space evolution of the electric field generated by an uniformly moving electron beam. The results we obtain, on a finite lifetime kinematical state, are compatible with an electric field rigidly carried by the beam itself.
16601897
Mechanisms affecting performance of the BaBar resistive plate chambers and searches for remediation
The BaBar experiment at PEPII relies on the instrumentation of the flux return (IFR) for both muon identification and KL detection. The active detector is composed of resistive plate chambers (RPCs) operated in streamer mode. Since the start of operation the RPCs have suffered persistent efficiency deterioration and dark current increase problems. The ‘‘autopsy’’ of bad BaBar RPCs revealed that in many cases uncured linseed oil droplets had formed on the inner surface of the Bakelite plates, leading to current paths from oil ‘‘stalagmites’’ bridging the 2mm gap. In this paper, a possible model of this ‘‘stalagmite’’ formation and its effect on the dark current and efficiency of RPC chambers is presented. Laboratory test results strongly support this model. ARTICLE IN PRESS *Corresponding author. Tel.: +1-609-258-4391; fax: +1-609-258-6360. E-mail address: changguo@princeton.edu (C. Lu). 0168-9002/03/$ see front matter r 2003 Elsevier Science B.V. All rights reserved. doi:10.1016/S0168-9002(03)01292-0 Based upon this model we are searching for solutions to eliminate the unfavorable effect of the oil stalagmites. The lab tests show that the stalagmite resistivity increases dramatically if exposed to the air, an observation that points to a possible way to remedy the damage and increase the efficiency. We have seen that flowing an oxygen gas mixture into the chamber helps to polymerize the uncured linseed oil. Consequently, the resistivity of the bridged oil stalagmites increases, as does that of the oil coating on the frame edges and spacers, significantly reducing the RPC dark currents and low-efficiency regions. We have tested this idea on two chambers removed from BaBar because of their low efficiency and high dark current. These test results are reported in the paper, and two other remediation methods also mentioned. We continue to study this problem, and try to find new treatments with permanent improvement. r 2003 Elsevier Science B.V. All rights reserved.
120513565
Measurement of inclusive two-particle rapidity correlations at the ISR
Abstract We present data on two-particle distributions in the approximate rapidity variable η = −1n tan θ /2 for secondaries produced in proton-proton collisions at the CERN Intersecting Storage Rings (ISR). The data at centre-of-mass energies of 23 and 62 GeV show the existence of energy-independent positive, short-range correlations between secondaries within the central region. Deviations from short-range correlation exist when one (or both) of the particles is near the boundary of the available phase space. In part, such deviations are interpreted as the effect of a diffractive-like component in multiparticle production.
121892713
Precision measurement of proton-proton total cross section at the CERN intersecting storage rings
Abstract The measurement of the proton-proton total cross section performed by the CERN-Pisa-Rome-Stony Brook Collaboration at the CERN ISR is discussed in detail. The total interaction rate, the elastic scattering rate in the forward direction, and the machine luminosity were measured simultaneously to obtain three different determinations of the total cross section. Consistent results were found, which made it possible to prove the reliability of the Van der Meer luminosity calibration within +-0.9% and to achieve a precision of +-0.6% in the measurement of the total cross section.
110772906
The use of waveform digitizers with drift chambers for D0
Abstract A prototype drift chamber cell with good space resolution, d E d x , and two particle separation has been constructed. A 100 MHz, 11 bit waveform digitizer readout scheme has been used for the tests.
123104321
Measurement of small-angle elastic scattering of pions and protons by nuclei
Targets made of C, Al, Cu, Pb, and U were exposed to ${\ensuremath{\pi}}^{+}$, ${\ensuremath{\pi}}^{\ensuremath{-}}$, and proton beams of 9.92 and 19.85 GeV/c (for $p$-Pb only) at the Brookhaven AGS. A magnetic spectrometer with spark chambers was used to detect elastically scattered particles in the Coulomb-nuclear interference region (5-35 mrad). Differential cross sections are presented and compared with an optical model, taking full account of multiple scattering in the target.
120319443
Associated multiplicities in proton-proton collisions with a charged hadron atX=0 at the CERN ISR
SummaryCharged-particle multiplicities and angular distributions associated with a π±, K±, p and 

$$
\bar p
$$

 produced at 90°, have been measured at the CERN ISR. The triggering particle was identified by a magnetic spectrometer, within a range of transverse laboratory momentumpT which was different for different particles: 0.075<pT<3.0 GeV/c for pions, 0.075<pT<1.5 GeV/c for kaons, 0.075<pT<3.0 GeV/c for protons and antiprotons. Associated multiplicities have been obtained as a function ofpT at the different ISR beam energies. The distributions of the associated particles have been studied as functions of the azimuthal angleϕ and of the pseudorapidityη. In the high-pT region associated multiplicities increase for all particle types approximately linearly withpT. The momentum of a high-pT particle is seen to be balanced over a wide cone ofϕ andη in the opposite hemisphere. An increase in the multiplicities of secondaries in the same hemisphere near the triggering particle is also observed for the high-pT baryons. At lowpT there is an increase in associated multiplicity on the same side as the transverse momentum of the pion approaches zero.RiassuntoSi presentano le misure effettuate agli ISR del CERN delle molteplicità e distribuzioni angolari delle particelle associate a π±, K±, p e 

$$
\bar p
$$

 prodotti a 90°. La particella di trigger è identificata da uno spettrometro magnetico in grado di analizzare i seguenti intervalli di momento trasversopT nel laboratorio: 0.075<pT<3.0 GeV/c per i π, 0.075< <pT<1.5 GeV/c per K e 0.075<pT<3.0 GeV/c per i protoni e gli antiprotoni. Si studiano le molteplicità delle particelle associate in funzione dell’impulso trasversopT delle particelle di trigger alle varie energie dei fasci circolanti negli ISR. Si studiano anche le distribuzioni delle particelle associate in funzione dell’angoloϕ e della pseudorapiditàη. Ad alto impulso trasverso le molteplicità associate crescono pressapoco linearmente con l’impulsopT. L’impulso di una particella ad altopT è bilanciato su un ampio cono in ϕ e η nell’emisfero opposto. Ad altopT e quando la particella di trigger è un barione si osserva una crescità nella molteplicità delle particelle associate nello stesso emisfero e a piccolo angolo Δϕ e δη rispetto al barione di alto impulso. A bassopT la molteplicità delle particelle associate ai π aumenta quandopT tende a zero.РеэюмеB ЦEPHe на ISR были иэмерены множественности эаряженных частиц и угловые распределения, ассоциированные с π±, K±, p и 

$$
\bar p
$$

, рожденными под углом 90°. Триггерные частицы идентифицируются с помошью магнитного спектрометра в области поперечных импульсовpT в лабораторной системе, которая является раэличной для раэличных частиц: 0.075<pT<3.0 ГзB/c для пионов, 0.075<pT<1.5 ГзB/c для каонов, 0.075<pT<3.0 ГзB/c для протонов и антипротонов. Были определены ассоциированные множественности как функцииpT при раэличных знергиях ISR пучка. Было проведено исследование распределений ассоциированных частиц как функций аэимутального углаϕ и псевдобыстротыη. В области больщихpT ассоциированные множественности увеличиваются для всех типов частиц приблиэительно линейно сpT. По-видимому, импульс частиц с больщимиpT является скомпенсированным в щироком конусеϕ иη в противоположной полусфере. Для барионов с больщимиpT также наблюдается увеличение множественностей вторичных частиц в полусфере около триггерной частицы. При малых рT имеет место увеличение ассоциированной множественности в ту же сторону, как и в случае, когда поперечный импульс пиона стремится к нулю.