LAV status report for the NA62 LAV working group Preliminary test beam results Future activities Progress on simulation A. Antonelli INFN-LNF SPSC meeting CERN 23 November 2009

LAV “Post-card” 12 LAV stations mounted along 120 meter decay region 6 meters apart 4 different types: –160, 240 blocks; 5 layers in vacuum –240 blocks; 4 layers in vacuum –256 blocks; 4 layers in air Angular coverage 7-50 mrad Inefficiency < from few hundred MeV to 35 GeV Building blocks: OPAL calorimeter lead glass blocks, for a total of 2500 crystals 2007 efficiency measurements with electron beams: 1-  <10 -4 for 200 MeV<E<500 MeV A. Antonelli INFN-LNF SPSC meeting CERN 23 November 2009 A1-A11 Vacuum

ANTI-A1 prototype In summer 2009 the first station A1 was built at LNF and shipped to CERN. It is now mounted on the blue tube A test beam run with the complete system including prototype front-end electronics (FEE) was performed at the end of October A. Antonelli INFN-LNF SPSC meeting CERN 23 November 2009

FEE requirements FEE time resolution (~500 ps) < lead-glass resolution Energy resolution ≈ 10%/√E Max rate ≈ MHz/ch (real rate/block < 100 KHz) Able to manage very large signals ≈10V Measure energy 20 MeV – 20 GeV in a single block Strategy Measure Time Over Threshold to evaluate charge Use custom TDC cards for the readout (HPTDC) Use Tell1 as TDC motherboard

Basic Ideas Build a low cost TOT system with large dynamic range –Use commercial devices (not a dedicated ASIC) –Clamp signal amplitude while maintaining original TOT (needs very fast low capacitance diodes) –Amplify the signal (x5) to increase slope and to enlarge signal width (>15 ns) –Compare the amplified clamped signal with a threshold to start and stop an LVDS signal –Use two different thresholds on each physical channel: - Correct for slewing online, improve sensitivity for large signals –Send the LVDS signal to the TDC

A. Antonelli INFN-LNF SPSC meeting CERN 23 November 2009 Front end electronics inputs (from detectors) 32 test out (to TDC) 5x

A. Antonelli INFN-LNF SPSC meeting CERN 23 November 2009 Front end electronics channel prototype boards have been built and used in the test beam

A. Antonelli INFN-LNF SPSC meeting CERN 23 November test beam results: Setup Entire veto with HV ON, use nominal values from equalization with cosmic rays 80 channels instrumented for readout: 16 per layer, summing up to 5 half-rings Dual readout: (active spitting) Clamping + discriminator board output  HPTDC Analog output  QDC (80 ch’s) Trigger with logical OR of signals from first half-ring (low-threshold discriminator) Dedicated DAQ, SPS signals used Can program trigger threshold for each channel remotely Raw files automatically transferred and decoded Online monitor to check veto activity, understand geographical map Instrumented

A. Antonelli INFN-LNF SPSC meeting CERN 23 November 2009 Validate time-over-threshold as readout method: Equalization procedure with muon runs: Equalize using QDC, compare results from TDC Study response for few-GeV electrons, compare with  Evaluate energy resolution, linearity of response Evaluate time resolution Validate Montecarlo simulation DATASET Muon runs 50 million Electron runs E = 2, 4, 6 GeV, 4 different positions in phi and different FEE threshold 2009 test beam results: Goals & Dataset

Online monitor Very useful tool, can check TDC or ADC activity in last burst Can plot single events or overall counters for previous burst Allowed easy fixing of the more obvious cabling mistakes

Preliminary analysis - QDC Select straight muons using isolation cuts Analyze single channels when all other cells in path fire Ch 17 Ch 19 Ch 21 QDC counts (4096 = 400 pC)

Preliminary analysis - QDC Check average MIP value and MIP width for each channel Offline cosmic-ray calibration gives a MIP of 45 QDC counts (4 pC)  MIP value  (QDC counts) Channel number 1 st layer  (MIP value) (QDC counts) First half-ring biased since it is used to form trigger (equivalent to ~30% of MIP)

TDC hit thresholds Fraction of events with at least 1 TOT hit vs QDC counts muon run Energy scale deduced from gain measured during calibration: 7 mV or 10 mV threshold values seem preferable 15 mV to 25 mV are too hard to be applied as single thresholds QDC counts Energy in block (MeV) mip

A. Antonelli INFN-LNF SPSC meeting CERN 23 November 2009 Time over threshold TOT Reconstruct TOT from closest pair of leading-edge/ trailing-edge hits from TDC Same dependence for each channel Muon run, 7 mV threshold Time over threshold (TDC counts) QDC-pedestal (QDC counts)

A. Antonelli INFN-LNF SPSC meeting CERN 23 November 2009 Time over threshold TOT Fit QDC vs TOT with a polynomial function Jumps due to ringing close in time to the signal, will be cured modifying the voltage divider Electron run 2 GeV Time over threshold (TDC counts) QDC-pedestal (QDC counts) threshold LVDS OUT

A. Antonelli INFN-LNF SPSC meeting CERN 23 November 2009 Equalization performances Offline cosmic-ray calibration gives a MIP 4 pC muon run Select straight muons using isolation cuts Reconstruct the charge from the time over threshold Mip from charge ant TOT gives compatible results

A. Antonelli INFN-LNF SPSC meeting CERN 23 November 2009 Time resolution 2 GeV electrons run Time differences between two subsequent blocks Slewing correction Q obtained from time over threshold Very preliminary  t singleblock=0.743/sqrt(2)=0.5 ns After slewing correction

A. Antonelli INFN-LNF SPSC meeting CERN 23 November 2009 Future work Comprehensively revising LAV design based on our experience in constructing and testing ANTI-1. Schedule is very tight: Must build and commission 11 LAV modules in years The complete set of designs will be ready by the beginning of 2010 All construction tools have been optimized to make this schedule feasible The front end electronics design will be frozen by the end of the year. Incollaggi o Wrappin g Banana

Simulation progress Geant4 Simulation of lead-glass, all details taken into account: wrapping, light guide, glue, photocathode dimension etc. Photon from Cerenkov light are tracked taking into account the appropriate distribution for: Absorption length vs E  Refractive index vs E  Reflectivity vs  Photoelectron from the photocathode are generated according to the photocathode efficiency vs

Response comparison We compared simulation with data taken at Napoli Cosmic Ray test stand in 2008 Z (M.I.P.) Simulation well reproduces quantitatively the data MC DATA

Fast simulation Parameterize the photoelectron emission efficiency with respect to photons position, direction and energy by means of a 4-dimensional matrix The matrix had variable size bins to reduce the size (38000 bins). The tracking of optical photons is slow (10-20 s / event) The execution times is 130 times smaller Fast simulation Detailed simulation

2008 Test First layer of blocks: Height Beam hit point Fototube Energy (MeV)Heigth (cm)BlockEvents Electrons beam, different energy and impact point

Prototype (electron) efficiency Inefficiency of DATA (red) and simulation (blue) with various experimental setups

Evaluate inefficiency for photons Create shower library Insert LAVs MC in the NA62 MC Next Step

A. Antonelli INFN-LNF SPSC meeting CERN 23 November 2009 Conclusions First LAV station was constructed and installed on the blue tube with success Preliminary analysis of test beam data was performed.,Encouraging results on the FEE performance have been obtained. Must build and commission 11 LAV stations in years (very tight schedule) Tools and construction procedures have been optimized to meet this schedule We have completed a detailed but yet fast simulation of the LAV system by parametrizing the optical photons tracking in G4 Comparison with experimental data available is encouraging