Using TileCal as a Luminosity Monitor

1. Using TileCal as a Luminosity Monitor Ilya Korolkov I.Korolkov Sep‘05 • Outline • Luminosity measurements at ATLAS and LHC • Min.Bias Monitoring System of TileCal • MBMing for Luminosity Monitoring

2. Luminosity measurements at LHC Ilya Korolkov 10% 5% Relative precision on the measurement of HBR for various channels, as function of mH, at Ldt = 300 fb–1. The dominant uncertainty is from Luminosity: 10% (open symbols), 5% (solid symbols). (ATL-TDR-15, May 1999) • Luminosity needed for: • Precision comparison with theory: • e.g.: bb, tt, W/Z, jet, H, SUSY, … • Cross section gives additional physics • information • Precision comparison with other expt’s • at LHC, TeVatron, LEP, HERA, … • Luminosity from: • LHC machine parameters & beam • instrumentation (~5-10%) • Rate measurements of precisely-calculable processes (1-2%)

3. Goals for the Luminosity measurements at LHC Ilya Korolkov • L/L goals: • LHC machine: 5-10%measurements of beam profiles and positions • ATLAS: ~2%normalization to Coulomb scattering (Roman Pots) • TOTEM/CMS: 1-2%using Ntotal|extrapl’d, dNelastic/dt |t=0, and the OT(forward trackers ~3<||<7 and Roman Pots) • LHCb: ~5-6%Nvtx=0/Nvtx1 rates, MC tuned with dN/d,tot, inel, SD 2% using b? • ALICE: pp: ~5%using Ninel (A=86%), MC extrapolation, and tot, inelHI: <10%(standard) 2%QED • L Monitoring: • using (dedicated) detectors (TileCal) & clean physics signals: e.g. W/Z leptons, …

4. Luminosity Topics in ATLAS Ilya Korolkov • Absolute Luminosity • Elastic scattering and Roman Pots • Options • W/Z counting • Machine Parameters • Machine parameters and size via vertex • Luminosity monitors (calibration issue) • LUCID • Options • Existing Hardware of Forward Calorimeter • Existing Hardware of TileCal • Minimum bias counter • Diamond

5. Monitoring by Counting Ilya Korolkov • Dedicated Luminosity Monitors: • LUCID counts primary forward tracks • Counting Physics Signatures • g g→ m+m- • With kinematic and vertex fit requirements plus Trigger  a statistical error of • DL/L < ~8 % per day(J.Pinfold, Rome’05) (nominal Lum?) • W → ln • At nom Lum the Rate is 60Hz (HLT bandwidth?)  a statistical error of • DL/L < ~1 % per 3min(J.Pinfold, Rome’05) • Z → l+l- • Similar to W->lv ? • TileCal min.bias Monitoring • a statistical error of DL/L < ~1 % per 0.1sec, nom Lum

6. Roman Pots in ATLAS Ilya Korolkov Fiber detector in RP 242m Roman Pots: One station per side, Two RP units per station Roman Pots

7. Fiber Detector Ilya Korolkov Design: ~ 1200 fibers glued and tilted at 45 degrees on both sides of the 170um base plate. ~ 200 PMTs for the signal collection. Final prototype by March 2006

8. Ilya Korolkov CDF CLC vs LUCID (J. Pinfold) ~150 cm Solution CDF Cerenkov light Collector Particle PMT Isobutane or C4F10 gas Al Mylar Cone Quartz fibre optic cable to transmit light to a remote PMT Solution LUCID Particle C4F10 gas Thin aluminium or carbon fibre tube

9. Ilya Korolkov CDF: CLC L Monitoring • Pointing Cherenkov cones: • sensitive to charged IP tracks, • ~blind to non-pointing secondaries • Real-time feedback to LHC control • Based on existing CDF design/operation; • Good linearity shown by CDF; CDF – superimposed data:L=2×1032, ~6 interactions/crossing

10. Ilya Korolkov LUCID (J.Pinfold Alberta) Dedicated detector: • bundle of projective Cherenkov cones: 5 layers of 40 tubes each • low mass (6 kg), rad hard (C4F10 ), quartz fiber readout • 40 MHz capability: no large extrapolation from L=1027 1034 • linearity required over 1-30 interactions/crossing • Counts primary particles • Mostly insensitive to non-primary particles • ~11 primary tracks per interaction • total signal  #charged primaries  interactions/crossing  L • Č-photon statistics & rad induced photons  • proof of principle: CLC at CDF(e.g. S. Klimenko et al., NIM A441 (2000) 266) • late on prototyping (2005?)

11. The LHC operation modes (in no way official) Ilya Korolkov • (short?) Machine tuning • (0.01->10)x1032 • Phase-0, 1st year to the ultimate performance • Tuning the machine performance from ‘physics’ official start-up to the ultimate values(0.1->2.3)x1034 • Runs dedicated to the Luminosity calibrations • (0. 1->1.0)x1028 • Phase-1, machine upgrade • IR upgrade is estimated to take place once a certain rad. damage of the quadrupoles at the IR is reached. Possible increase in luminosity to 1035 (SLHC). Several scenarios were proposed, some more to come. • Phase-2, machine upgrade • Possible energy upgrade + 1035 (VLHC). • 1027 - 1035

12. ATLAS Detector Ilya Korolkov Hadronic Tile Calorimeter Muon Spectrometer Solenoid 22 m Inner Detector Electromagnetic Calorimeter Toroid 44 m -

13. TileCal Geometry Ilya Korolkov The TileCal, the barrel part of the hadronic calorimeter of ATLAS, is a sampling device made of steel and scintillating tiles (4:1). Due to the LAR EM-calorimeter in front mainly the response to hadrons is optimized. Sensitivity to muons is used to enhance the muon tagging. An example distributions will be given for the cells: A13 – the most exposed to the min.bias events cell of TileCal, BC5 – typical TileCal cell, D0 – the least exposed to the min.bias events cell of TileCal. Hermeticity coverage 1.7 cracks at transition region Intermediate Tile Calorimeter + Gap Scintillators Segmentation Each 0.1 azimuthal slice consists of 73 cells arranged into projective towers with0.1. Each of 64X3 modules has three depth segmentations called samples A, BC, and D. y D D0 D0 D BC5 BC BC A A z A13 A13 BC5 5.6 degree azimuthal slice η=1.7

14. TileCal Single Channel FE Readout Ilya Korolkov DC Calibrations, Luminosity Monitoring Cesium In-situ Physics Tile Minimum Bias TileCal cell Fibre Laser Mixer HV PMT PMT Block HV Micro HV Opto Canbus Divider Charge Injection 3-in-1 L H Mother Board Digitizer Analog Integrator ADC-I Canbus Adder Digital Drawer Optical Interface TTC ROD Had Trigger µ Trigger Energy

15. Min.Bias Signals in TileCal (MC) Ilya Korolkov X.Portell Example of the energy deposition by min.bias events per collision in a given TileCal cell (MC) A1 Min.Bias events == inelastic pp collisions at low momentum transfer. -> Expected 23MB events per BXing at nom Lum (1034) -> Energy distribution is symmetric in  -> Mean Energy deposited in a given cell per collision is small -> Fluctiations of the deposited energy are rather large Simulations of the Min.Bias events in the TileCal are available at the cell level. This is a critical step to proceed with the system evaluation.

16. Min.Bias in the TileCal Cells per collision (MC) Ilya Korolkov Cell occupancies (chances for the shower to reach the cell) are <1%. Mean Energy is small and driven by the occupancy. Means in Sample A: (0.2-1.1)MeV Means in Samples B,D are much smaller RMSs are much higher than the means A13 Occupancy in the TileCal Cells per Collision Occupancy (%) BC5 D0 pseudo rapidity mean(E) in the TileCal Cells per Collision A13 RMS(E) in the TileCal Cells per Collision A13 mean(E) MeV RMS MeV BC5 BC5 D0 pseudo rapidity pseudo rapidity D0

17. Min.Bias in the TileCal Cells per bx (nom.Lum, MC) Ilya Korolkov A13 Cell occupancies and mean Energy roughly scale up by 23. Means in Sample A (5-25)MeV Means in Samples BC,D are smaller RMSs scale up roughly by sqrt(23). Occupancy in the TileCal Cells per bx Occupancy (%) BC5 D0 pseudo rapidity mean(E) in the TileCal Cells per bx A13 RMS(E) in the TileCal Cells per bx A13 RMS MeV mean(E) MeV BC5 BC5 D0 pseudo rapidity pseudo rapidity D0

18. Min.Bias Anode Currents in the Tilecal Cells (nom.Lum, MC). Ilya Korolkov 100pF -Vdac RF 2 MΩ PMT RIN OP Vout TO SHAPER I = f x k x Re / (e/pi) x E I(Lum) = 28nA/MeV x E(Lum) where E(Lum) is the energy deposited in the given cell per bx, f is bx frequency = 40MHz, k = 2808/3564 = 0.79 is correction for empty bunches other coefficients are measured at the TBs: Re = 1.157pC/GeV is (pC/GeV) ratio for electrons at 20o e/pi = 1.3 is the ratio to scale Re to the pion level DC currents from TileCal Cells A13 I, nA BC5 D0 I pseudo rapidity By setting the RF to (1-100)MΩ one will obtain measurable Vout around 1V.

19. FE: Slow Current Integrator (G.Blanchot) Ilya Korolkov 100pF Signal build-up on the integrator (MC) -Vdac RF 2 MΩ PMT RIN OP Vout 5 msec TO SHAPER RC measurement, data X.Portell • DC coupled to PMT with permanent coupling to the shaper • Build around input stage operational amplifier • Gains (RF) are selected • remotely through 3in1 logic • Gains, offsets and linearities can be • calibrated by a dedicated charge • injection system (Vdac) • Local output switch • controlled by the 3in1 logic • Radiation Tolerant • Part of the 3in1 card controlled • through the TTC and CAN • -> Dynamic range for the anode currents: • 12pA = 1ADC count at the highest Gain • Saturation at the lowest Gain at 1773nA • -> RC = 10msec

20. FE: ADC (G.Blanchot) Ilya Korolkov • 12 bits digitizer, (0-5)V dynamic range • Global Pedestal Control Feature • Local Integrator Enable Input for • distributed readout • CANbus port. • Radiation tolerant. INTG_SEL INTG_OUT 3in1 Logic INTG_GND 3in1 Logic 3in1 Logic Pedestal Control Analog Bus DAC Micro ADC CANBus Port 3in1 Cards Control Logic Differential Input Stage 3in1 Cards Controls

21. Accuracy of a single measurement of the min.bias anode currents from a given Cell (nom.Lum, MC). Ilya Korolkov Accuracy of a single measurement of the min.bias anode current for a given TileCal cell can be estimated from the energy spread per bx and number of bxs per the integration time. For the nominal Luminosity: Accuracy in Sample A ~ 1% Accuracy in Sample B ~ (1-3)% Accuracy in Sample D ~ (2-9)% If systematic effects, such as beam-gas interactions, are not taken into account, this would give an estimate on the stat. error of the relative luminosity measurement. Accuracy of a single measurement of the min.bias anode current for a given TileCal cell D0 Acc (%) BC5 pseudo rapidity A13

22. Luminosity reach for a single channel & accuracy of a single measurement Ilya Korolkov Luminosity X 1034 Anode current (nA) as a function of luminosity A13 Luminosity reach for a single channel is limited by the ADC+Gains dynamic range: ADC saturation at 1770 nA 10ADC counts = 0.12 nA Overall performance is optimized for the nominal luminosity. At the low luminosities the statistical sum of many channels of the TileCal should improve the accuracy. The <1% accuracy should not be taken seriously for the systematic effects are not considered. BC5 I (nA) D0 Luminosity X 1034 D0 A13 Acc (%) Stat accuracy (%) of a single measurement as a function of luminosity BC5

23. Partitions, Readout chain Ilya Korolkov DCS Four Partitions of the TileCal = four “TTC” Crates (in USA15): CCT VME CPU TTCvx, TTCvi modules Read-Out Buffer (RB) per crate / partition Local network • There are 4 MBMing Partitions in the TileCal. • Each partition consist of: • CCT, TTCvi, RB. • Each RB controls 4 CAN lines configured to 250kbps. • There are 16 ADC-I CAN nodes per line. • ADC per TileCal module. • There are 45 (36) channels controlled by each ADC-I in the Barrel (EB) module. Four CAN lines per RB: <170m (including daisy chain), 250 kbps, 16 nodes. LV_CAN_PS to be produced by CF. Sixteen ADCs (CAN nodes) per CAN line Mezzanine board TTC control CAN control 3in1 bus Control over 3in1 45 integrator cards per ADC (barrel) PMT block

24. Readout Cycle, Stat Accuracy per Sweep per Partition Ilya Korolkov The system reads out 1 channel per module following single trigger, which takes place every 50msec, as defined by SHAFT calibration board of TileCal. => 256 channels are read out per single trigger. Max Luminosity update rate == 50msec. Luminosity X 1034 The cycle to read out all channels in the partition (45chs/module (~36chs/m) in the Barrel (EB) partition) is called sweep. TileCal is divided into 2 Barrel and 2 EB partitions. Every cell is read out twice (from two sides) per sweep. Hence, once the readout bandwidth is equally divided between all the channels, one sweep will take 2.5sec (2.0) for the Barrel (EB) partition. Barrel Partition accuracy (%) stat accuracy (%) from single sweep of barrel partition If the monitoring task of the TileCal will permit, an extra readout bandwidth can be given to the sample A channels (more sensitive to the min.bias interactions) at the expense of the cells in the samples BC&D. This will enhance the stat accuracy, Lum < 1032.

25. Related Part of the TileCal DCS Ilya Korolkov 3 cylinders of TileCal UX15 analyzes, stores the data PVSS? PVSS? USA15 preprocess (compress?) the data Atlas control room presents summary The CCT CPUs, located in the TTC crates, one per TileCal partition, will read the data from the RBs. The functions of further data transmission, analyses and data storing will be spread between the CCTs and 1-2 dedicated TileCal DCS stations depending on their performance. The DCS related tests scheduled to start in September 2005. Only short summary will come to the TileCal DCS station in the ATLAS control room.

26. Components Summary Ilya Korolkov ~10k integrator cards produced (Chicago), burned-in, QC-ed, installed in the drawers, tested, >85% installed in the modules, tested & certified. 270 ADC-I cards v.5 produced (Barcelona), burned-in, QC-ed , installed in the drawers, tested, >85% installed in the modules, tested & certified. 20 VME-CAN compressor (RB) boards of v.2 are produced (Barcelona) and QC-ed. 6 RBs are currently used at CERN. The CAN cable length seems currently under control (<170m), The cable length defines communication speed (250kbs) which in turn limits the read-out rate. CAN power supplies are in production (Clermont-Ferrand). The TCal calibration board, known as SHAFT, that has to provide suitable triggers to the three online Calibration systems of the Tile Calorimeter (CIS, LAS, MBMing), is under design.

27. Ilya Korolkov 25nsec run Normal run Tests The performance of the integrator and ADC-I cards, and the RB boards was extensively tested since 1999 in many TileCal groups, during the Cs certification of the modules and during ten TileCal TB periods. System functionality test was performed at the CTB: M.Volpi Normal and “25nsec” beam profiles as seen by the system

28. TileCal WP12 (barrel, 2005) Ilya Korolkov The commissioning of the mim.bias monitoring system is a part of the TileCal phase-1 commissioning plan as Work Pakage 12. We aim for three goals (for the TileCal barrel) by the end of 2005: 1) Integrate all final readout components into the system and certify communication with ADC-Is. 2) Integrate the min.bias code with the TDAQ and DCS of TileCal. 3) Integrate MBMig system with CIS and LAS systems.

29. Calibration at 1027-1028 ? Ilya Korolkov • Below Lum=5x10^29, less than a single min.bias hit/cell/10msec is expected in every cell of the TileCal, including the sample A cells. The histogram of the values measured from the integrator becomes of a peculiar type containing two distinguished parts: • 1) Pedestal events when no hits happened in the cell during the integration time, with the Gaussian shape directly measurable on pedestal events. • 2) Signal tail spanning several ADC counts (~80MeV/ADC count), with the shape that is result of convolution of • - min.bias deposition spectrum - not known (but from MC) • - RC response function - directly measurable • - noise Gaussian as in the pedestal events - measurable • Neither of two parts change shape as the Lum go lower. What does change is the ratio of the entries. If one could decouple the part of the signal tail (we have to do studies on it. D0 will be in this mode upto 10^32), one can use it’s mean value for the absolute calibration on given channel. • - 1% stat error on the mean with the data from 30 (300) hours at Lum=10^28 (10^27), 240 channels at 20Hz. • - Gains can be set to x3 (x8 may be) by HV system. • - Have to study if OP amplifier gains can be increased. X.Portell Example of the energy deposition by min.bias events per collision in a given TileCal cell (MC) A1 Calibration of the system at L=(10^27-10^28) would be very challenging but may be possible. We need to do dedicated studies on the options.

30. Ilya Korolkov Low Frequency noise Sigrid & Iacopo

31. Summary Ilya Korolkov The min.bias monitoring system, dedicated to monitoring the performance of the TileCal optics and read-out, might be used as one of the lum monitors of ATLAS. The system is based upon anode current integrators that are attached to every readout channel of the TileCal. The read-out of the integrators is not a part of the standard ATLAS readout. The system performance is optimized for the nominal luminosity (1034). The stat. error on the relative luminosity measurement per sweep (2.5sec) is expected to be ~12% for L=1030, ~4% for L=1031, <1% for L=(1032-1035). Calibration of the system at L=(1027-1028) would be very challenging but may be possible. We need to do dedicated studies on the subject. The frequency of the update on the relative luminosity from the system will depend on the demands and computing resources available.

32. Summary Ilya Korolkov Most of the hardware components used in the system are produced and were tested over the years. The readout software is under development, a prototype had been tested at the Combined Test Beam 2004. The commissioningof themonitoringsystem is part of the TileCal phase-1 commissioning Work Packages.