Luminosity Monitoring OUTLINE Luminosity ONline and OFFline Luminosity

Luminosity Monitoring OUTLINE • Luminosity ONline and OFFline • Luminosity measurement in ALICE: • V 0, T 0 and ZDC (for heavy-ions) • LHC Luminometers • Trigger, DCS and Monitoring Tapan Nayak Aug 10, 2006 Offline Meeting

Luminosity: Online & Offline • Luminosity ONLINE: • Measurement using V 0, T 0, ZDC (for heavy-ions) and LHC Luminometer • Luminosity calculated ONLINE from measured values (1 st order estimation without detailed corrections) • Online display and monitoring • Feedback to LHC: luminosity, vertex sizes …. • Write to our data-stream • Luminosity OFFLINE: • Calculation of absolute luminosity with all corrections • Effect of short term (in every fill) and long term luminosity changes • uncertainty in luminosity to be properly calculated • available in the data-stream for physics Aug 10, 2006 Offline Meeting

Luminosity Measurement We will measure the rate, d. N/dt, of a given process with cross section, s. We need to determine the efficiency (e) of the detector for the process and the acceptance (A). Knowing these, the luminosity can be obtained from the above expression and monitored during data taking. Both efficiency of the detector and acceptance have to be determined with proper error estimation in these quantities in the presence of upstream materials. In ALICE, luminosity will be monitored by: • V 0 • T 0 • ZDC (for heavy-ions) • LHC Luminometer Aug 10, 2006 Offline Meeting

V 0 and T 0 V 0 A (Left) V 0 C (Right) T 0 Left T 0 Right 340 90 -350 +70 h - coverage 2. 8 to 5. 1 -1. 7 to 3. 7 4. 5 to 5. 0 -2. 9 to -3. 3 # of channels 32 32 12 12 84. 78 37 ps z-position(cm) Active area(cm 2) Time resolution 1 ns V 0 C V 0 A T 0 -L RB 24 Aug 10, 2006 Offline Meeting IP T 0 -R RB 26

V 0: Beam-Beam & Beam-gas interactions BGA t. V 0 A< t 0 Aug 10, 2006 t 0 t. V 0 A> t 0 BB t. V 0 C> t 0 Offline Meeting BGC t. V 0 C< t 0

Luminometer at Point-2: The LETI Cd. Te detector Aug 10, 2006 Offline Meeting Enrico Bravin

Status of Cd. Te detector • The design of the detector has been ready for a while… Technology stretched to the limit in terms of rad-hardness can not be used in IP 1 and IP 5 • Design of mechanical supports undergoing (probably the same moveable support for IP 2 and IP 8) • Decision to proceed with this technology taken only at the end of 2005 …Order to LETI sent end of April • LETI needs about 12 months to produce 4 monitors… looks just ok, delivery of first monitor expected for end October 2006 • Front end electronics could be off the shelf, in any case it is just a simple linear preamplifier. In contact with ATLAS (BCM) • For the acquisition system we hope to use the DAB as for the IC thus profiting from the development done by LBNL Aug 10, 2006 Offline Meeting

Cd. Te detectors integration The Cd. Te detector goes here beyond a Cu block of between 4 and 20 cm depth IP How about ALICE ZDC? Is it going to be OFF for pp? ? Aug 10, 2006 Offline Meeting

Compatibility of ZDC with LHC luminometer Nora De Marco • The compatibility depends on the amount of converter necessary for the luminosity monitor Luminosity Monitor Z ZPN 2 IP • LHC luminometer may be used in H. I. runs if compatible with ZN TCTH D 2 Aug 10, 2006 Offline Meeting 9

Questions regarding the Luminometer and BCM 1. Can the response of Luminometer be simulated or is it needed? Is it needed to calculate the acceptance and efficiency? The simulation of the response of the Luminometer is in progress. Details will be provided to us afterwards. 2. Slow control for the luminometer: this will be done by LHC group. 3. How do we get the information to ALICE-DAQ or ALICE-monitor? This information comes to us from LHC. Presently the Luminosity number is planned to be sent to us every bunch. We should get an integrated number, in addition. Need to know about BCM of ALICE – Mark Tavlet is working on that. Aug 10, 2006 Offline Meeting

ALICE to provide: • Luminosity / Rates – MB triggers from V 0 give MB interaction rate (using CTP counters) – Translation from rates to luminosity …. • Position and size of luminous region – Can we get these data from V 0 or T 0 online? (z only !) – ITS online (~ 1 sec rate) ? Aug 10, 2006 Offline Meeting

Monitoring of Luminosity 1. DCS: V 0, T 0, ZDC, ITS, (Luminometers(? ), BCM(? )) 2. We need to monitor important beam related parameters 3. Values to be communicated to LHC by DCS Mood • V 0 • counts • active channels …. • acceptance, efficiency • T 0 Calculated from V 0 / T 0: Aug 10, 2006 • counts • active channels …. • acceptance, efficiency • ITS • #of track hits, tracklets • Vertex in x, y, z • ZDC …. • LHC Luminometer • Estimated Luminosity Offline Meeting

Scheme for Online Monitoring of Luminosity With: Giacinto de Cataldo & Filimon Roukoutakis Pierre Vande-Vyvre and Alessandra Mazzoni ALICE DCS LHC_DCS INF_LHC Preliminary suggestion ZDC T 0 V 0 detector DAQ Main data stream CTP TMLuminosity MOOD Interaction record, scalars Aug 10, 2006 Offline Meeting 13

Issues related to Luminosity 1. 2. 3. 4. Luminometer for point-2 and compatibility with ZDC Time scale for Luminometer, BCM Trigger definitions: proper strategy for startup Luminosity Monitoring • How the information is shared? • Implementation 5. Sending information to LHC 6. 7. 8. 9. Aug 10, 2006 Offline readiness Simulation of beam-gas, pileup Simulation of acceptance, efficiency, etc. Calculation of vertex online: x, y, z • Where is it processed and how it will be sent to monitoring and to LHC? Offline Meeting