Bland, R

Hodges, Christopher L

Huntington, J

CERN Document Server

QQSBUEC OCR Output3 Physics Dept., San Francisco State Univ., San Francisco, USA2 Lawrence Berkeley Laboratory, Berkeley, USAl Physics Dept., Univ. of California, Irvine, USA1986G E N E V AContactman: P. Sonderegger, 4670 or l3-7042Spokesman: G. ShawH. Pugh‘, M. Savage°, G. Shaw* and A. SteinerR. Bland°, C. Hodges°, J. Huntington°, H. Matis‘,Irvine—LBL—San Francisco State° Collaborationl2A SEARCH FOR QUARKS PRODUCED IN HEAVY-ION INTERACTIONSPROPOSAL TO THE SPSC.¤%$ · Q4. SCO0O00519am I `Y I20 F ebruar Yé 1 lllliillhll IIINIMIIIIMHI NSPSC/P 220£gC;?CERNlJBRARHE,GENEVA4QF}? CERN/SPSC 85-76¤ S2O)El Q} OfEUROPEAN ORGANIZATION FOR NUCLEAR RESEARCHc¤¤r·/1:> vm OCR Output- 2particles with color are confined. Models have been presented inlocal symmetry in nature is SU(3)C°txU(l)em, in which case°lpresent theoretical and experimental results whether the exactHowever, it is not possible to determine definitively fromtheories confine the charges of the local—symmetry group.theoretical investigations that unbroken non—Abelian gaugeconfinement. We accept the widely held belief based on manytheoretical literature supporting the doctrine of quarkThere is an enormously impressive body of experimental andI. Theoretical Background and Other Quark Searchesbeam particles.conservatively, will be sensitive to one quark produced per l0or molecules will remain in the distillate. This experiment,the accelerator beam, and depends on arguments that quarked atomsThis involves distilling the mercury which has been exposed toexperiment we enrich the sample of mercury (by a factor ~l0°Lsearches have been published. To enhance the sensitivity of thisrunning well for six years and null results for fractional chargeoil drops. The SFSU automated Millikan apparatus has beennet charge, with a technique similar to that used by Millikan ontesting macroscopic samples of matter (mercury) for non—integralproduced in particle interactions. Our method is based onnovel technique to search for fractionally charged particlesmembers of this collaboration at other accelerators. We use acollisions. This proposal is a continuation of work done byexciting new environment of ultra—relativistic heavy-ionWe propose to search for fractional charges produced in theA SEARCH FOR QUARKS PRODUCED IN HEAVY-ION INTERACTIONSSPSC/P 220 OCR Output.. 3 ..on the moon over its lifetime. Furthermore, the techniques ofheavy primary cosmic rays of energy >200 GeV/A incident per cmincident per cmf in this experiment is more than the number ofNote that the more than 10oxygen (and sulphur) ions13fractional charges.energy in this non-equilibrium sea to create and free these lightbeam hitting a heavy target. Further, there should be enougha sea l/m ~2-3 fm could readily be<:reated with the CERN oxygen__ 59 gluons to be less than the size of the sea. Thus the size ofthe separation of fractional charge, we need the range l/m of thegluon sea created in the heavy—ion collision to enhance greatlysmall as a few GeV. In order for the (non-equilibrium) quarkmight be as large·" as 75—l00 MeV with a corresponding Q mass asm isnot woconstrained byexperiment“as inother models*,andproduced. As a result of the composite structure of the diquark,fractionally charged, glow singlet, color 6 diquarks Q can bethe eight gluons acquire a mass m for which free, low—mass,collisions.* In the glow model,SO(3), of broken QCD, five of2 gthe accurate bounds set in much higher energy elementary particlefractional charge production that is not at all in conflict withtremendously important, completely new environment for freepresently designed CERN 225 GeV/A ion beam presents aFrom our theoretical considerations,’ we believe that thecreated in a heavy—ion collision.may be greatly enhanced in the environment of a quark-gluon searemaining colored fragment in the vacuum, the separation processdifficult to separate a particle with fractional charge from theto elementary—particle collisions. That is, where it isgreatly enhanced in relativistic heavy-ion collisions as comparedsuggestedj that the production of free fractional charge might beviolate present experimental constraints. In fact, it wasdiquarksz) could be produced in certain experiments and yet notexact local gauge symmetry. Here free quarks (or perhapswhich SU(3)is spontaneously broken·and color is not anl2C°l°ISPSC/P 220 OCR Output, 4hadrons) is larger than that of ordinary colorless hadrons due tois especially true if, as expected, the quark interaction (withfront of the tank and) in it might also be stopped there. Thissubstantial fraction of all free fractional charge produced (insmaller than we would have proposed, we believe that athe space provided by NA38. Although the volume of mercury isThe dimensions of the cylinder are taken to be compatable withheavy-ion run in 1987.will remain in the NA38 beam stop until the end of the secondcourse, the highest A ions being of most interest. The cylindercylinder will simply add to possible quark production with, ofAll types of beam particles and at all energies incident on outthe total number of beam particles incident on the NA38 target).new resources or funds. No monitoring is required (outside ofsegment of the NA38‘s W beam stop, this experiment requires noof the NA38 beam stop. Since this cylinder simply replaces onediameter and containing ~3 kg of mercury placed in the front partis incidentcxia stainless steel cylinder 20 cm long and 5<:m inThe apparatus to be used at CERN is shown in Fig. l. The beamA. Apparatus to be used at CERNstop, no new resources or funds are required from CERN.since the cylinder will simply replace a segment of the NA38 beamthese three parts of the experiment in turn. We stress thatapparatus of San Francisco State University. we will discussused at Lawrence Berkeley Lab, and the automated Millikanto be used in the exposure at CERN, distillation equipment to beThis experiment requires a small cylinder containing mercuryII. The Experimental Apparatusanalyzed.this experiment allow for concentrations of ~l0° for the materialSPSC/P 220 OCR Output..5The mercury still has been built at SFSU, according to asufficient to retain the quarks.it appears that the image-charge binding energy is more thanK.E. = kT/2 = .02 eV ,Celsius,to the thermal energy per degree of freedom at 100 degreesP.E. = q‘/d = .16 eV ,1/3 of an electron, 5 angstroms from the mercury surface,Comparing the image charge energy of a particle, with a charge ofquarks will be retained in the residue by the image charge force.in sea water due to evaporation.° When the mercury is distilled,molecules was first suggested by George Zweig for concentrationwill remain in the residue. This property of quarked atoms orthat any fractionally charged particles deposited in the mercuryFor the distillation scheme to be effective, we need to assume»— radioactivity will not be a problem in the CERN exposure.10800-GeV protons at Fermi1ab° indicates that induced15apparatus, and the residual radioactivity after exposure to aboutresults in a liquid which can still be measured in the Millikanexperiment. Distillation by at least four orders of magnitudeapparatus. We have distilled mercury from our 1985 Fermilabmilligram of this residue will be measured in the Millikandropper of the SFSU Millikan apparatus). Then about onemilligrams or so of material (the amount needed to fill thewill be reduced afterwards by distillation to a hundredThe 3 kilograms of mercury exposed to the CERN heavy-ion beamB. The distillation apparatusits extended color field.- 6 OCR Outputmercury in the dropper. The potential of this wire (a few volts)charge on the drops near zero, a bias wire is inserted into theaccuracy of about 3.8% of e as shown in Fig. 3. To keep theThe charge on an 8-micron—diameter mercury drop is measured to anmicrograms of mercury can be measured in an hour of good running.Drops can be measured atezrate of one per second, and twentyand rejected.Drops which change charge during the measurement are identifiedredundant, allowing reliable rejection of badly measured drops.charge of each drop is determined. The measurement is highlyswitching the field polarity in mid-measurement, the mass andcontrolled and data are collected by an on—line computer. Bydrop over a series of slits (Fig. 2). The measurement ismeasured by timing the passage of an image of the illuminatedThe drop's drift velocity in a switched electric field istime into a measuring chamber by a piezoelectric drop ejector.oil·drop experiment in which small drops are introduced one at aThis measuring apparatus is a modification of the MillikanC. The SFSU Millikan Apparatusdistillation.radioactive Hg) remains in the small drop left after2O3radioactivity in the original target mercury (outside oflarger than lO“ are now readily achieved. Essentially all theFermilab experiment is currently being distilled there. FactorsLaboratory, where the still is set up. Mercury from theThe distillation will take place at Lawrence Berkeleymaintains a steady pressure during distillation.vapor. A vacuum pump (vented into an appropriate filter)itself is grounded. A condensing column liquefies the mercuryliters in volume surrounded by a heating mantle. The mercurySan Francisco. The still consists of a glass vessel about 2design based on commercial stills used by Quicksilver Products ofspsc/P 220- 7 OCR Outputthat the hadronic interaction of free quarks is the same as forin the NA38 beam stop. (In estimating the stopping, we assumeefficiency*of·»01.for the small cylinder of Hg that we will haveextrapolations of those results, we estimate a stoppingCarlo for another experiment by R. Slansky.° Based on reasonableFor mercury, the stopping efficiency has been modeled by Monterejection.Here the factor of l/2.3 allows for the 90%—confidence—levelparticles a quark a stopped quarkS = ( beam )x(for stopping)x( for observing )x(l/2.3)number of efficiency efficiencysensitivity expected of either detection scheme is given byrejected by a null experiment with 90% confidence. Theof the ratio of beam interactions to quarks produced which can beWe define the sensivity of our experiment as the largest valueIII. Sensitivity of the Measurementanalyzed.milligrams of material.The Fermilab° Hg is now beingl0our search in native mercury and have measured another 2at the Bevalac (500 micrograms)”. We are currently continuing(50 micrograms)? and one in mercury exposed to a heavy ion beamsearches, one in native mercury (l80 micrograms){ one in waterthe past 6 years. We have published results of three nullsearching for free fractionally charged particles (quarks) forThe San Francisco State University quark group has beenmost of the roughly 20% rejection rate of single measurements.accepted. Rejection of charges outside this range accounts foris adjusted by the computer. Drops with charge between *25e arespsc/P 220- 8 OCR OutputWe note that all the parts of this process have been tested.months.this exposure, all targets were able to be shipped in fourradiation damage observed in the steel mercury containers. For60°C. After an exposure of about 50 x 10protons, there was no13protons/pulse, the maximum temperature of the mercury targets wasspill of 20 seconds. At the highest intensity run, 3xl0 llThe 800 GeV/c proton beam was pulsed every 60 seconds with a beamalready been run at Fermilab in the high—intensity proton beam.Similar apparatus to that described in this proposal has2xl0beam interactions/quark.= 8S = (l0) x (.0l) x (.005) x (l/2.3)l3exposure,observation efficiency becomes 0.005. Thus, for a 10-particle130.5 mg of this is measured in the Millikan apparatus, theabout the smallest sample which can be conveniently handled. Ifdistilling by a factor of 3xl0“, down to a sample of 100 mg,distillation by a factor of l0“ already. We see no obstacle toin the drop ejector of the Millikan apparatus. We have testedconcentrating too much<iirtiJ1the mercury*to be able to run itefficiency depends on the degree of distillation possible withouteven for a wide variety of production mechanisms. The detectionon the production mechanism, it should not decrease dramaticallygreater than presented hereJ While this is slightly dependentactual sensitivity could be at least an order of magnitudeactually proportional to the quark mass. In this case, thethat of ordinary hadrons due to their extended color field, andcolorless hadrons. However, it is quite likely to be larger thanSPSC/P 220- g OCR Outputcollisions.»— with the accurate bounds set in higher energy elementary particleenvironment for producing quarks that is not at all in conflictCERN heavy-ion beam offers an exciting, completely newadditional funds or resources from CERN. We believe that thetank forms part of the NA38 beam stop and thus requires noquark per 2xl0° beam interactions may be obtained. Our mercuryautomated Millikan apparatus. A sensitivity to better than onedistillation technique, and searched for using the proven SFSUare collected and concentrated in mercury samples, using ain relativistic oxygen/sulphur collisions with mercury. QuarksWe have described a method of detecting free quarks producedV. ConclusionSPSC/P 220- 10 —OCR OutputM.L. Savage et al, to be published in Physics Lettersl0M.A, Lindgren et al, Phys. Rev. Letters 51, 1621 (1983)DAL Joyce et al, Phys. Rev. Letters 51, 731 (1983)<2Jh Hodges et al, Phys. Rev. Letters 47, 1651 (1981)George Zweig, Science 201, 973 (1978).A. Hahn et al, Fermilab proposal P747.Particle Data Group's references.4l (1977). For a complete listing of free-quark searches see theNuc. Phys. B10l, 349 (1975);bL Basilo et al, Nuovo Cimento 40,See, e.g., the very accurate ISR experiments, C.W. Fabian et a1,G.L. Shaw and R. Slansky, Phys. Rev. Letters 50, 1967 (1983)(1981)R.S1ansky,'T.Goldman and Gin Shaw, Phys.Rev.Letters 47,887(1978)A.DeRujula,ILC.Giles,and Rin Jaffe,Phys.Rev.D17,286REFERENCESSPSC/P 220made from stainless steel. OCR OutputFigure 1-1: Schematic for mercury target. The cylinder is100 mm ———>(end view)*%wfield occur at slits 39 and 74. OCR Outputtypical mercury drop. Reversals of the electricFigure 2: Drift velocity as a function of position for aPosition (slit number)40 BO'5 IOis I *mE' n IOCR Output20discernible irbm ?hteqec`chatq@§ drops(0.03&E). the frectional charged drops are clearlyblack. with the mgasure§.charg§ resolution¢¤¤¤· The ¢¤mP¤§&r qe¤&taced~events are shadedfrhctional charqqi events-superimposed on thatangiyzed sample of mercury with cdmputsr simulatedQ Figure 3: Disgributimn of the resEHMal charge for anFI °d Ich uniis "eI ESI UG GYQIE ( QIU, 102 10

A search for quarks produced in heavy-ion interactions

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