BRAHMS Status and Run Plans March 23, 2000 HENP PAC presentation F.Videbœk Physics Department Brookhaven National Laboratory for BRAHMS Collaboration

March 23,2000 Overview of presentation Physics Goals of BRAHMS Detector Overview and Status –Overall layout –Status, pictures, readiness Year One (FY 2000) Expectations –Examples of First Year Measurements –Outline of First Year Run Plan Year Two (FY 2001) Outlook

March 23,2000

BRAHMS Physics Goals Measurements p, K,  identified in wide range of rapidity, 0 < |y| < 4 and 0.2 < p t < ~ 3GeV/c (central and fragmentation region). Measure semi-inclusive p t spectra as function of centrality. Study this as function of collision system (Au, Si, p+A, and p+p) Capabilities for BE measurements. Results will address Reaction Dynamics. Stopping, chemical equilibrium, thermalization. p,p-bar production. Baryo-chemical potential K+,K-. Strangeness enhancement. vs dN/dy. Mini-jet production systematic; rapidity dependence (p t > 2 GeV/c p, K,  ).

March 23,2000 Early Physics Goals (Au+Au) Stopping –Baryon number transfer in rapidity Different mechanism in HI reactions like Gluon junction or di- quark breaking mechanism may result in higher transfer than simple extrapolations from pA will indicate. –Energy transfer from beam to central region. A rapidity shift in baryon kinematically corresponds to an energy loss. This energy can show up as increased particle production at mid-rapidity, or carried by high rapidity particles. –Model prediction vary different.

March 23,2000 Early Physics Goals Global measurements – multiplicity measurements, and correlation's with forward neutrons. Hadron spectra, rapidity distributions and , K, p yields for soft p t region Aim to record as much data for these purposes as feasible with machine and detector performance in this first year with lots of uncertainty for machine and detector performance.

March 23,2000 Approximate pt max for year one Pion semi-inclusive acceptance

March 23,2000 Perspective View of Spectrometer zdc

March 23,2000 Tracking and PID Forward Spectrometer è2.3 o <  < 30 o Coverage Full Forward Spectrometer (2.3 o <  < 15 o ) High-momentum mode –sweeping D1,D2 –tracking and momentum determination by T2-T5, D3,D4 –PID: RICH (  /K/p) separation < 25 GeV/c) Tof-H2 (  /K < 5, K/p < 8.5 GeV/c with 4  cut) Low-momentum mode –tracking and momentum determination by T1-T2, D2 –PID: C1 (  /K) separation < 9 GeV/c) Tof-H1 (  /K < 3.3, K/p < 5.7 GeV/c with 4  cut Front Forward Spectrometer (15 o <  < 30 o ) –Same as Low-momentum Mode Momentum resolution  (dp/p) ~ 1% Mid-Rapidity Spectrometer è30 o <  < 95 o Coverage Tracking and Momentum determination, MTP1,MTP2 and D5. PID TOFW (  /K < 2.2, K/p < 3.7 GeV/c with 4  cut). Essentially one charge measurements.

March 23,2000 BRAHMS Present Configuration The forward spectrometer is fully instrumented with its detectors, but is only capable of powering the magnets to about half field thus restricting the coverage in phase-space. The Front Forward Spectrometer (FFS) consisting of 2 magnets D1 and D2, and associated detectors moveable from 3-25 degrees. Will not go to 2.3 in this year. The Back Forward Spectrometer (BFS) consisting of 2 magnets D3 and D4 and associated detectors Mid Rapidity Spectrometer (MRS) consisting of MTPC1 and MTPC2 and TOFW (4 modules covering one charge). Global Detectors -The Centrality detector consisting of an inner layer of Si-detectors and an outer layer of large scintillator. -The Beam-Beam counter array. -The Zero Degree Calorimeters (ZDC) -The si-detectors will not be installed until stable beam operations. Several detectors have been installed since last summer, and has never seen RHIC beams.

March 23,2000 Spectrometer System 2 O’clock IR viewed from DX (FS) IR overview (MRS, Central)

March 23,2000 Forward Arm Back detectors T3 T4 Rich H2 D4

March 23,2000 Beam Beam Counters Installed in IR Left Array Right Array Data from circulating beam.

March 23,2000 Application of beam beam counters Multiplicity measurements Beam-gas background events rejection

March 23,2000 Multiplicity Measurement and Detector Hybrid Detector consisting of two layers of 168 channels of Si-detector channels 40 segments of 12*12 cm scintillator tiles –5mm thick; individual readout using fibers by PMT. –Design based on CDF, STAR calorimeter tiles. coverage -2.2 <  < 2.2

March 23,2000 Tile Response The tiles has been calibrated using cosmic rays in the IR. A top bottom coincidence was made Expect about 200 hits for central Au-Au per tile. ~ 1Mip

March 23,2000 C1 Cherenkov Detector and FS TOF C1 –Threshold Segmented Cherenkov Detector using C 4 F 10 at 1.2 atm. –32 individual cones with H 1161 PMTs. –Gives pi/K separation up to 9 GeV/c H1 –48 - 1cm slats read out by 3/4” PMT –gives PID for mainly low momentum (p <6Gev/c) measurements. C1 T2 H1`

March 23,2000 The TPCs have a short drift (20 cm) using ArCO 2 (90:10) Each detector has about 1000 pads readout with STAR FEE electronics, and a BRAHMS VME receiver board TPCs T1 on Platform 9U-VME TPC receiver board Receiver boards in FeHut

March 23,2000 TPC performance In recent months, in part due to problems, extensive cosmic ray measurements has been performed with T1. Cosmic rays are about 40% single track, 60% showers. Reconstructed tracks from such event. Clusters in single pad row. Track density is about 50% of expected MAX track density at the most forward for this detector. Very encouraging for this years measurement.

March 23,2000 MRS spectrometer 3 (4) 21 slat modules of TOFW MTPC1 D5

March 23,2000 Back Forward Spectrometer DC, H2 and RICH T3 Drift Chamber. Installed Feb 2000, construction in Cracow. RICH on Platform PMT array cabled up RICH H2

March 23,2000 Detector Status Summary Global Detectors –ZDC, BB, and Multiplicity Tiles checkout with beam and cosmic rays. –Si-detector. Lab checkout. Tracking Detectors –TPC have now all been checked out with either tes beam ( ,e) or cosmic rays. –Performance in RHIC with high track density and luminosity unknown. –Drift Chambers T3,T4,T5 installed on platform. Some electronics and cabling still to be done. Expect operation later in run. Not needed for first measurements. TOF systems –H1,H2, TOFW installed, and checked with sources. Prototypes all had satisfactory time resolution (80 psec). Cherenkov Detectors –C1 installed and ready since summer. –RICH just installed.Filling with C4F10/C5F12 to be completed. PMT array in place.

March 23,2000 Detector Status summary Magnets & Platforms –All 5 have been run and tested at full field. Will operate at up to half field. –Angle positioning ‘readout’ in place. Remote movement possible. Trigger system. –Partial commissioned during summer –Setup for Min Bias events initially with provisions for centrality selection. DAQ –Integrated readout of Camac (6/7), Fastbus (1/4) and TPC (2/4), intermediate storage on buffer disks, and transfer to RCF HPSS system has been established. –The system has been used successfully in two Brahms dry runs in February and March as well as in RCF transfer tests where sustained rates of 4 Mb/sec were achieved. Offline –Tracking reconstruction using the ROOT framework have reached a mature status. –Acceptance and PID code for first physics analysis is nearing completion.

March 23,2000 Multiplicity correlation The ‘resolution’ of the simple Multiplicity array is even with a small number of elements quite good for Au on Au.

March 23,2000 Min Bias Acceptance (Fritiof 7.02)

March 23,2000 BRAHMS Goals for FY2000 Running Period  Commissioning of global detectors, trigger systems and detecting Au-Au collisions.  Commissioning of full detector system. Particular the tracking and PID detectors. The spectrometer sections will be dealt with separately.  Engineering. Before making high quality physics measurements it is necessary to understand the operations of detector system under stable beam conditions to study and evaluate –Beam collisions, beam gas background collisions –Detectors backgrounds at different spectrometer settings –Trigger (Beam-Beam counters and Multiplicity array).  Physics  Global multiplicity distributions and correlation's with ZDC data.  The integrated luminosities for physics measurements (Acc+det) will most likely be small in FY2000. Two scenarios  ~ 15  b -1 ( May-August)  ~ 4  b -1 ( June-July)  Never the less first measurements of Au-Au Spectra at selected angles (~ y= 0,1, 2,3 ) for a set of magnetic field settings using both spectrometers. This should yield information of rapidity distributions in central/min bias for pions, protons and kaons at pt<= 1.2 GeV/c.

March 23,2000 BRAHMS Goals for FY2000 Running Period  Kaon measurements will not have the statistics this year as envisioned in last year RBUP.  A set of higher statistics runs to obtain more complete pt-spectra and extending to higher pt if running time allows. This will aim to get high statistics spectra of both central, min bias and peripheral collisions for protons, kaons in addition to pions at selected rapidities and p t up to about GeV/c. The commissioning of detectors will be interspersed with physics data taking utilizing sub detector systems. E.g. The first global data can be taken with the spectrometer operation is optimized. The commissioning of detectors may take up to 8 weeks with beam, but will be distributed over a longer period.

March 23,2000 Outlook for Fy2001 Primary Goal will be to carry out a high statistic and quality survey at 100Gev/c AuAu collisions. During FY2001 the Forward Spectrometer should be capable of measuring the high momentum part of spectra following the addition of a sub-station at 2 o’clock requested in the FY2001 budget. The Time-Of-Flight wall in the MRS will be extended to full coverage, allowing simultaneous detection of positive, negative charged hadron. This as well as the increased luminosity make HBT measurements using both MRS and FS feasible. A survey of another collisions system as well as initial measurements of pp system.

March 23,2000 Access and other considerations Several short access periods <2h are expected during the commissioning phase for configuration changes, adjustments and repairs. Brahms will not install si-detector until routine beam collisions are achieved. This requires only 1-2 shifts, and can be done incrementally. The Drift Chambers installed will be to be readied for use during the middle part of the run. Requires access periods for cable hook-up. Considering the shortened running time this year we will not request time to move spectrometer to 2.3 deg, but will settle on the present established lower limit of 3 deg.

March 23,2000 Conclusion Brahms is ready to commission detector system and make the first physics measurements. The experience and analysis of data taken this year will form additional basis for planning of measurements in the FY2001 running period.