Results are presented from a test beam study of the D0 liquid argon end calorimeter electromagnetic module prior to its installation at the Fermilab Tevatron Collider. Using electron beams with energies ranging from 10--150 GeV we have obtained an energy resolution of 15.7%/{radical}E(GeV) with a small constant term of 0.3% and a linearity of better than {plus minus}0.5%. The position resolution of the calorimeter is found to approximately 1 mm for 100 GeV electrons. 7 refs., 8 figs., 3 tabs

Spadafora, A.L.

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Lawrence Berkeley National LaboratoryLBL PublicationsTitleTest Beam Results from the D0 Liquid Argon End Calorimeter Electromagnetic ModulePermalinkhttps://escholarship.org/uc/item/1kn0t1ndAuthorSpadafora, A.L.Publication Date1991-08-01eScholarship.org Powered by the California Digital LibraryUniversity of CaliforniaLBL-31168 Lawrence Berkeley Laboratory UNIVERSITY OF CALIFORNIA Physics Division Presented at the 5th Pisa Meeting on Advanced Detectors, Elba, Italy, May 26-31, 1991, and to be published in the Proceedings Test Beam Results from the DO Liquid Argon End Calorimeter Electromagnetic Module A.L. Spadafora August 1991 Prepared for the U.S. Department of Energy under Contract Number DE-AC03-76SF00098 - --!-+on o .... r 'i '1 C) n > ~J::: :z: .... :If! III n IDt+Q ID ID "t1 ~[I) -< [I) - --to .... 0-I,Q . U1 s r .... O"n '1 0 III "'0 '1"< "< . I\) r to r I W t-t-IJ) (X) DISCLAIMER This document was prepared as an account of work sponsored by the United States Govemment. While this document is believed to contain conect information, neither the United States Govemment nor any agency thereof, nor the Regents of the University of Califomia, nor any of their employees, makes any wananty, express or implied, or assumes any legal responsibility for the accuracy, completeness, or usefulness of any information, apparatus, product, or process disclosed, or represents that its use would not infringe privately owned rights. Reference herein to any specific commercial product, process, or service by its trade name, trademark, manufacturer, or otherwise, does not necessarily constitute or imply its endorsement, recommendation, or favoring by the United States Govemment or any agency thereof, or the Regents of the University of Califomia. The views and opinions of authors expressed herein do not necessarily state or reflect those of the United States Govemment or any agency thereof or the Regents of the University of Califomia. LBL-31168 TEST BEAM RESULTS FROM THE DO LIQUID ARGON END CALORIMETER ELECTROMAGNETIC MODULE1 Anthony L. Spadafora Lawrence Berkeley Laboratory University of California Berkeley, CA 94720 August 1991 1 This work was supported by the Director, Office of Energy Research, Office of High Energy and Nuclear Physics, Division of High Energy Physics of the U.S. Department of Energy under Contract DE-AC03-76SF00098. Test Beam Results from the DO Liquid Argon End Calorimeter Ele~tromagnetic Module Anthony L. Spadafora* Lawrence Berkeley Laboratory University of California Berkeley, California 94720 USA Representing the DO collaboration t August 12, 1991 Presented at the 5th Pisa Meeting on Advanced Detectors Elba, Italy, May 26-31, 1991 Abstract Results are presented from a test beam study of the DO liquid argon end calorimeter electromagnetic module prior to its installation at the Fermilab Teva-tron Collider. Using electron beams with energies ranging from 10 - 150 Ge V we have obtained an energy resolution of 15.7%/JE(GeV) with a small constant term of 0.3% and a linearity of better than ±0.5%. The position resolution of the calorimeter is found to be approximately 1 mm for 100 Ge V electrons. ·This work was supported by the Director, Office of Energy Research of the U.S. Department . energy under Contract No.DE-AC03-76SF00098. tThe DO collaboration includes members from Universidad De Los Andes Colombia, University of Arizona, Brookhaven National Laboratory, Brown University, University of California Riverside, Columbia University, Centro Brasileiro de Pesquisas Fisicas Brazil, Fermi National Accelerator Lab-oratory, Florida State University, University of Florida, University of Hawaii, University of Illinois Chicago, Indiana University, Institute for High Energy Physics Serpukhov USSR, Iowa State Uni-versity, Lawrence Berkeley Laboratory, University of Maryland, University of Michigan, Michigan State University, New York University, Northern Illinois University, Northwestern University, Uni-versity of Notre Dame, Purdue University, Rice University, University of Rochester, CEN Saclay France, State University of New York - Stony Brook, Tata Institute of Fundamental Research Bombay India, Texas A&M University, University of Texas at Arlington and Yale University. 1 1 Introduction The DO experiment, which will begin taking physics data in the 1992 run of the Ferrnilab Tevatron Collider, features a uniform, fine-grained uranium liquid argon calorimeter which provides good energy resolution and hermetic coverage for elec-trons, photons and jets. A test beam facility has been established at Fermilab to study the response of the electromagnetic and hadronic modules that comprise the central (CC) and end (EC) calorimeters (Fig 1.) This paper will present results from the test beam study of the response of the end calorimeter electromagnetic mod-ule (ECEM) to electron beams. The response of the combined electromagnetic and hadronic modules to pion beams can be found in Ref.[l] and test beam results from CC modules in Ref.[2, 3]. 2 The ECEM Module The ECEM module, shown schematically in Fig.2, provides full azimuthal (¢» cov-erage in the forward region (1.4 < 1] < 4.0)t. In order to minimize losses due to internal cracks, the module is built as a single unit: both the signal boards and the absorber plates are preassembled as disks of typically 1 m radius and then stacked to assemble the module. The basic sampling cell of the module consists of a 4 mm depleted uranium absorber plate, a 2.3 mm liquid argon gap, a NEMA G-10 signal board and another 2.3 mm liquid argon gap. A more detailed description of the mod-ule's construction can be found in Ref.[4]. Signals are read out in four longitudinal sections and transverse segmentation is provided by semi-projective towers of ap-proximately square pads of l:11] x l:1¢> = 0.1 x 7r/32(';::j 0.1). In the third longitudinal section, which typically contains 65% of the electromagnetic shower, the transverse segmentation is doubled in both directions (0.05 x 0.05) to provide better shower -t 7J is ~he pseudorapidity defined as 7J = -In tan( () /2), where () is the polar angle from the beam axis. 2 position resolution. See Table 1 for a summary of the readout segmentation. 3 Test Beam Setup The DO calorimeter test beam facility has been established in the Fermilab Neutrino-West beam line which provides electron and pion beams with momenta from 10 to 150 GeV Ic. A system of proportional wire chambers (PWC's) and Cerenkov counters provides particle momentum and identification on an event-by-event basis. The spread of the beam momentum is typically 1.5% (measured to an accuracy of 0.2%) and the pion contamination in the electron beam is negligible (less than 10-5). A set of scintillation counters provides the trigger. The test beam run described here was performed with the final DO ECEM and ECIH (end calorimeter inner hadronic) modules prior to their installation at the collider. The test beam cryostat has a thin window (two 1.6 mm thick steel plates) in the region illuminated by the beam and was configured with a liquid argon excluder, a 2.5 cm thick stainless steel plate to simulate the DO cryostat walls, and a 4.4 cm thick aluminum plate at small angles to simulate the DO vertex detector endplates and electronics. The test beam cryostat is equipped with a computer controlled transporter that orients the module so that the beam strikes it along projective towers as do particles at the collider. The region illuminated by the beam (±15 degrees in ¢> and the full extent in "1) and a surrounding border zone were instrumented with the readout electronics (1452 channels in total) and internal cryostat cables which will be used in the final DO detector. The overall sensitivity [5] of the electronics is ,..,., 0.57 fC per ADC count or 3600 electrons per count. 3 4 Test Beam Results The analysis of the calorimeter data proceeds by first correcting for the electronic channel pedestals and gains, which were measured once per eight hours and once per day, respectively. The pedestal widths vary with the channel capacitance but were about 8 MeV for a typical 2 nF cell. The spread in the beam momentum was corrected event-by-event using the momentum measured by the PWC system. The energy of electromagnetic showers was reconstructed by summing all four lon-gitudinal sections in the ECEM and the first section of the ECIH. Relative sampling fractions for each longitudinal section were obtained by simultaneously minimizing the energy resolution and the deviation from linearity for electron momenta ranging from 10 to 150 GeV Ic. These optimized values, shown in the last column of Table 2, are not very different from the relative values calculated from minimum ionizing dE I dX losses. The analyses presented here used a single set of energy independent relative sampling fractions. The number of towers summed to contain an electro-magnetic shower varies with Tf, corresponding to .the variation of pad size with Tf. For example, for intermediate size pads of 5 cm square, 99.5% containment is achieved by summing an array of 5 by 5 towers, while for pads of 1 cm square an array of 9 by 9 towers is needed. "Benchmark" runs at a selected point in the module (Tf = 1.95) were repeated almost daily to monitor the stability of the apparatus. For the three month duration of the run the mean value of the response for 100 Ge V electrons was found to be constant with an rms spread of 0.3%. The results of a high voltage scan with 100 GeV electrons is shown in Fig. 3. Our operating voltage of 2.5kV (11 kV Icm) is well located on the plateau. The curve in Fig. 3 is a fit to the form of Ref[6] and yields an estimate of the oxygen contamination of 0.52 ± 0.03 ppm O2 • Such scans were repeated approximately every ten days and 4 no measurable change was found. Clear signals for muons were seen in the calorimeter arising from the appro xi-mately 3% muon component of the hadron beam. A muon peak is distinguishable above pedestal in all longitudinal sections of the calorimeter. The pulse height spec-trum for 15 GeV muons in the third EM layer is shown in Fig. 4. From the fitted most probable value of the muon spectrum in each layer, we obtain an average value of 9.8 ± 0.1 ADC counts/cm of liquid argon. Comparing the ratio of pulse height to deposited energy for electrons and muons, we find for 15 GeV muons: PH(e)/E(e) e//l = PH(/l)/E(/l) = 0.69 ± .05 Pulse height distributions from electrons of various beam momenta are shown in Fig.5. The mean value in ADC counts of the Gaussian fits are shown in Fig.6a as a function of beam energy and, in Fig. 6b, the residuals from a linear fit of the form: /l(cts) = Ebeam(GeV) X (263.0 ± 0.1) cts/GeV - (23 ± 4) cts The fractional energy resolution, calculated as (T / /l from a Gaussian fit, is shown in Fig. 6c. We assume the energy dependence of the resolution is of the form ((T / /l)2 = C2 + 32 /E+ N 2 /E2, where E is the beam energy in GeV, C is a constant contribution from systematic errors such as remaining channel-to-channel variation in gain, 3 is due to the statistical error in sampling, and N represents energy independent contributions to (T such as electronic and uranium noise. The results of the fit are: C = 0.003 ± 0.002, 3 = 0.157 ± 0.005( y'GeV), and N = 0.329 ± 0.030(GeV). The the noise term, N, is consistent with the value obtained for an array of 5 by 5 towers from the pedestal widths. The small pads (widths range from 1.4 cm square to 5 cm square) of the third EM layer are used to obtain a measurement of the shower transverse shape and impact position. The one-dimensional shower profile can be written as a sum of "core" and "tail" exponential terms: 5 where Xo is the shower impact position. The fraction of the shower energy that is found to one side of a pad edge is calculated from the double exponential form to be: ER _ Iooo ~ _ 1 _ alb2e-bllxol + a2ble-b2lxol - 00 dE -E tot Loo dX 2(al~ + a2bt) (Xo> 0) where ER and' Etot are the energy to the right (i.e. increasing x) of a pad edge and the total energy, respectively. Using the shower impact position projected from the track trajectories measured with the PWC system independently of the calorimeter, we fit for the double-exponential parameters and obtain the results given in Table 3. For determination of the position resolution we use the center of gravity algorithm with a correction term to remove the bias with distance of the shower from a pad edge. Approximating the shower transverse shape by a single exponential term, the corrected center of gravity is given by[7] b . h 1 (Xc - Xm . h~) X = Xc + sm - ~ sm b where Xc = the x coordinate of the shower center of gravity, Xm = pad center, ~ = pad halfwidth, and b is the single-slope characteristic length for which we have found 5 mm to be the optimum value. This algorithm is somewhat simpler than the double exponential technique and yields the same value for the position resolution. The resolution obtained for 100 GeV electrons and pads 2.5 cm square in the third EM layer is shown in Fig. 7 as a function of X e , the distance from the pad edge. The dependence of the resolution on Xe is fit by a quadratic form: u = ao + a2x~ where ao = (0.081 ± 0.001) cm and a2 = (0.023 ± 0.002) cm. Applying this analysis to data taken at varying beam energies, we obtain an energy dependence of the position resolution averaged over the pad of approximately: u = (1.3 ± O.l)cm x E(-0.61±.02) where E is in GeV. 6 Although the above measurements of energy and position resolution were obtained at selected spots in the calorimeter, we have taken uniformity scans to verify that such performance can be achieved throughout the module. The results of a scan in azimuth (<p) at a constant "I is shown in Fig.8. The mean response is constant to 0.5%. Data was also taken scanning the only two sources of non-uniformity in response: the tie-rods that penetrate the stack and the small crack between the uranium plates. The regions affected by these features comprise only a few percent of the active area of the module. 5 Conclusion The performance of the DO end calorimeter electromagnetic calorimeter module was studied using electrons with energy ranging from 10 to 150 GeV. The calorimeter response was found to be uniform across the instrumented area and stable for the duration of the run. The energy resolution is 15.7%/JE (GeV) with a small constant term of 0.3% and the response is linear to better than ±0.5%. A position resolution for the localization of electromagnetic showers of 1 mm is achieved for 100 Ge V electrons impacting on a tower edge. I would like to thank H. Aihara, W. Dharmaratna, and N. Roe for their contribu-tion to the analyses presented in this paper. The DO Calorimeter group would like to thank the Fermilab Accelerator Division and the staffs at our individual institutions for their contributions to the success of this project. This work was supported by the Director, Office of Energy Research of the U.S. Department of Energy under Contract No. DE-AC03-76SF00098. 7 References [1] N .Amos, Proceedings of the International Conference on Calorimetry in High Energy Physics, Batavia, IL Oct. 29 - Nov. 1, 1990, to be published. [2] M.Abolins et al., Nucl. Instr. and Meth. A280 (1989) 36. [3] P.Franzini, Nucl. Instr. and Meth. A289 (1990) 438 [4] A.Spadafora, Proceedings of the International Conference on Calorimetry in High Energy Physics, Batavia, IL Oct. 29 - Nov. 1, 1990, to be published. [5] M.Demarteau, Proceedings of the International Conference on Calorimetry in High Energy Physics, Batavia, IL Oct. 29 - Nov. 1, 1990, to be published. [6] J.Engler et. al., Nucl. Instr. and Meth. 120 (1974) 157. [7] G.A.Akopdjanov, et. al., Nucl.lnstr.and Meth. 140 (1977) 441; A.DeAngelis and F.Mazzone, Nucl. Instr. and Meth. A287 (1990) 397. 8 Table 1 : Longitudinal and transverse segmentation of the ECEM readout. Layer # Cells Absorber ~TJ x ~¢> EMI 2 1.6 mm Fe 0.2Xo .1 x .1 EM2 2 4mmDU 2.6Xo .1 x .1 EM3 6 4mmDU 7.9Xo .05 x .05 EM4 8 4mmDU 9.2Xo .1 x .1 Table 2 : The sampling fractions calculated for a minimum ionizing particle, these values normalized to the third EM layer, and the relative values found from the resolution/linearity minimization. The values in parentheses were not varied in the fit. dE/dX Fit Layer SF ~ SF i *ffi SF i EMI .047 1.82 1.61 EM2 .090 0.96 0.96 EM3 .086 (1.0) (1.0) EM4 .081 1.06 1.10 IHI .056 1.52 (1.52) Table 3: The fitted shower shape parameters from the double exponential form. The amplitude of the second term, a2, is set equal to 1. al 3.71 ± .09 bl (2.87 ± .7) mm a2 1.00 b2 (10.3 ± .1) mm 9 Figure Captions Fig.1 The DO liquid argon calorimeters. Fig.2 The ECEM Module. Fig.3 High Voltage plateau curve of the ECEM taken with 100 GeV electrons. FigA Pedestal subtracted pulse height spectrum for 15 GeV muons in the third EM layer. Fig.S Pulse height distributions of electrons for various beam energies, normalized to the same number of events. Fig.6 a) Mean pulse height as a function of beam energy, b) residuals from a linear fit, and c) fractional energy resolution as a function of beam energy. Fig.7 Position Resolution of the ECEM as a function of the distance from edge of a pad. u is the rms of the difference between the corrected center of gravity impact position in the third EM layer and that projected from the track reconstructed from the PWC's. The fit is the quadratic form given in the text. Fig.8 Mean pulse height for 100 GeV electrons runs at a fixed TJ but varying azimuth. The azimuth is given as the arc length at the calorimeter S = R x <p where R for this scan is 59 cm. 10 END CALORIMETER CENTRAL CALORIMETER Figure 1: 11 Fine Hadronic Electromagnetic Outer Hadronic Figure 2: 12 25000 20000 rn +> ~ ~ 0 15000 t) t) Q < 10000 5000 O~~~-L~~~L-~~~-L~~~ o 1 2 3 Voltage (kV) Figure 3: 13 300 200 100 EM LAYER 3 M.P.V.=22.64+-0.15 ADC Channels Figure 4: 14 ~ 0 .~ ~ ::i ..c .~ M ~ rn .~ 't:I 't:I Q) N .~ ...... ttl S M 0 Z 300 10 GeV 250 25 GeV 200 150 50 GeV 75 GeV 100 GeV 125 GeV 100 150 Ge 50 o~~~~~~~~~~~~~~~~~~~~~~ o 10000 20000 ADe counts Figure 5: 15 30000 40000 ..-.. u 40000 ~ '-" ~ ..c:: 30000 bD ....... Q) ::t: Q) 20000 a) rn ...... ::s 0.. 10000 ~ ~ Q) ::El 0 0 50 100 150 Beam Energy 0.010 ~ 0.005 b) ....... rz.. .......... ..-.. ~ ....... 0.000 rz.. I rn ~ Q) :::iI -0.005 '-" -0.010 0 50 100 150 Beam Energy 0.12 0.10 0.08 ~ 0.06 b 0.04 0.02 0.00 0 50 100 150 Beam Energy Figure 6: 16 0.150 0.125 ! i 0.100 i ...-S 0.075 C) --b 0.050 0.025 0.000 -2 -1 0 1 2 Distance Xe from Pad Edge (cm) Figure 7: 17 en o+J ~ ;j 0 C) u Q <t: 28000 ...... 27000 26000 25000~~~~~~~~~~~~~~~~~~~~~ -200 -150 -100 Azimuth S Figure 8: 18 -50 0 50 - R x ¢ (mm) LAWRENCE BERKELEY LABORATORY UNIVERSITY OF CALIFORNIA INFORMATION RESOURCES DEPARTMENT BERKELEY, CALIFORNIA 94720 

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Test Beam Results from the D0 Liquid Argon End Calorimeter Electromagnetic Module

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Test beam results from the D0 liquid argon end calorimeter electromagnetic module

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Test beam results from the D0 liquid argon end calorimeter electromagnetic module

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