Henri Videau LLR Ecole polytechnique - IN2P3/CNRSCalor Calorimetry optimised for jets Henri Videau Jean- Claude Brient Laboratoire Leprince-Ringuet Ecole polytechnique - IN2P3/CNRS Contribution to the session on jet calorimetry CALOR2002 Calorimetry optimised for jets

Henri Videau LLR Ecole polytechnique - IN2P3/CNRSCalor Calorimetry optimised for jets The physics programme for a coming electron linear collider is dominated by events with final states containing many jets, dijets from H, W, Z. We contend that, in the energy range under consideration, the best approach is to optimise the independent measurement of the tracks in the tracker, the photons in the electromagnetic calorimeter and the neutral hadrons in the calorimetry, together with a good lepton identification. This can be achieved with a good tracker and a high granularity calorimetry providing particle separation, through an efficient energy flow algorithm. But we do not contend that this is a universal panacea Studying that program from the calorimetric side on hardware and software issues is the goal of the CALICE collaboration

Henri Videau LLR Ecole polytechnique - IN2P3/CNRSCalor Calorimetry optimised for jets radiative qq at 500 GeV WW at 800 GeV Jets at the linear collider _

Henri Videau LLR Ecole polytechnique - IN2P3/CNRSCalor Calorimetry optimised for jets The analytical energy flow approach has been widely used at LEP but LEP detectors had some draw- backs ALEPH coil in the middle poor longitudinal segmentation 2d digital read- out in the HCAL and the energy ditributions are quite similar projective cracks

Henri Videau LLR Ecole polytechnique - IN2P3/CNRSCalor Calorimetry optimised for jets Impact of the jet resolution on the physics programme Parametrising 6 jets L=1 ab  1  = 0.6  3   = 0.3  6  in the separation ZZ / WW  0.3  0.6 = loosing 45% of L  0.3  0.6 = loosing 40% of L a lot more work to assess the effect on all the programme work in progress

Henri Videau LLR Ecole polytechnique - IN2P3/CNRSCalor Calorimetry optimised for jets separation ZZ / WW

Henri Videau LLR Ecole polytechnique - IN2P3/CNRSCalor Calorimetry optimised for jets Reminder on the analytical energy flow basics The energy flow of a jet is written as the sum of its components Such a method relies more on separation of particles than on intrinsic energy resolution Argument  the charged particles make about 60% of the energy and, being of rather low energy, are much better measured by the tracker Isolate the 10% neutral hadron energy  far enough from the interaction point small radiation length small interaction length matched granularity Inside coil Compactness seeing the mips

Henri Videau LLR Ecole polytechnique - IN2P3/CNRSCalor Calorimetry optimised for jets To profit from that we need a good tracker, not so much on momentum resolution but good track efficiency, small rate of fake energetic tracks good V0 identification small rate of reinteraction a good electromagnetic calorimeter, not so much on resolution but good photon efficiency, even close to tracks small rate of fakes from hadronic debris good electron identification (prompt) a good hadron calorimeter to identify muons to disentangle neutral hadronic showers from charged ones to measure their energy

Henri Videau LLR Ecole polytechnique - IN2P3/CNRSCalor Calorimetry optimised for jets Elements for a solution concerning the calorimetry Density, good separation electromagnetic/hadron sandwich tungsten / silicium 24 X0 no projective cracks 40 layers thickness < 20 cm cells matched to the Moli ₩ re radius ~ 1 cm2 good efficiency to mips. noise ~ 1/10 mips Radiator adapted to separation/resolution small cells read digitally ECAL HCAL A solution with scintillating tiles is also studied within CALICE

Henri Videau LLR Ecole polytechnique - IN2P3/CNRSCalor Calorimetry optimised for jets Aspect of the detector

Henri Videau LLR Ecole polytechnique - IN2P3/CNRSCalor Calorimetry optimised for jets Effect of going from iron to expanded tungsten Resolution Separation

Henri Videau LLR Ecole polytechnique - IN2P3/CNRSCalor Calorimetry optimised for jets Old results

Henri Videau LLR Ecole polytechnique - IN2P3/CNRSCalor Calorimetry optimised for jets

Henri Videau LLR Ecole polytechnique - IN2P3/CNRSCalor Calorimetry optimised for jets Are these performances kept at high energies? All the studies presented here have been done using Mokka an application on Geant4 The jet energies have been obtained in a multi step process knowing the extrapolation of the charged tracks reconstruct the photons in the Ecal subtract the cells of these photons identify the hadrons estimate the energy of the neutral hadrons through a neural net Different other approaches: thermodynamical or neural net This is the cornerstone of jet calorimetry

Henri Videau LLR Ecole polytechnique - IN2P3/CNRSCalor Calorimetry optimised for jets X generated  's 8 + charged 4 * neutral had. 1 O reconstructed  's Seeing a W dijet impact on the first 4 X 0 of the calorimeter in  projection The square is 100 mrad wide

Henri Videau LLR Ecole polytechnique - IN2P3/CNRSCalor Calorimetry optimised for jets number of reconstructed  's versus number of generated  's Some results at 800 GeV on photons

Henri Videau LLR Ecole polytechnique - IN2P3/CNRSCalor Calorimetry optimised for jets GeV Energy distribution for true photons and reconstructed ones including fakes

Henri Videau LLR Ecole polytechnique - IN2P3/CNRSCalor Calorimetry optimised for jets Energy distribution of generated true photons and reconstructed true photons GeV A reconstructed photon is associated to a true one if more than 75% of its energy comes from it.

Henri Videau LLR Ecole polytechnique - IN2P3/CNRSCalor Calorimetry optimised for jets Difference between the true photon energy and the reconstructed one per event. The fit is done with 2 gaussians. Norm Mean GeV  GeV Norm Mean GeV  GeV  2 /dof = 1.1 GeV

Henri Videau LLR Ecole polytechnique - IN2P3/CNRSCalor Calorimetry optimised for jets GeV Photon reconstruction efficiency at low energy

Henri Videau LLR Ecole polytechnique - IN2P3/CNRSCalor Calorimetry optimised for jets GeV Photon reconstructed energy versus true energy

Henri Videau LLR Ecole polytechnique - IN2P3/CNRSCalor Calorimetry optimised for jets Energy photons/evt kin versus rec. Distribution of event photonic true energy and reconstructed

Henri Videau LLR Ecole polytechnique - IN2P3/CNRSCalor Calorimetry optimised for jets Distribution of event photonic true multiplicity and reconstructed

Henri Videau LLR Ecole polytechnique - IN2P3/CNRSCalor Calorimetry optimised for jets GeV Neutral hadron energy distribution

Henri Videau LLR Ecole polytechnique - IN2P3/CNRSCalor Calorimetry optimised for jets A more complete reconstruction of the jets at high energy is under way.

Henri Videau LLR Ecole polytechnique - IN2P3/CNRSCalor Calorimetry optimised for jets Few more informations about the digital HCAL solution. The sensitive detector A gas detector, compact, efficient to mip, high signal and cheap! Streamer or Geiger wire detector RPC's i nformation from DHCAL subcollaboration: IHEP, Interphysica, LLR, MEPhI, Seoul U.

Henri Videau LLR Ecole polytechnique - IN2P3/CNRSCalor Calorimetry optimised for jets Gap 1.2 mm Glass plates 1 mm TFE/N2/IB 80/10/10 Efficiency to mip > 98% Pads outside Pads inside Signal on 50  : 3 V 1x1 cm 2

Henri Videau LLR Ecole polytechnique - IN2P3/CNRSCalor Calorimetry optimised for jets Scheme for a digital HCAL signal detection Fe or.. Fe Chip PCB Spacers Glass Pad insulating layer insulating layer resistive layer conductive layer

Henri Videau LLR Ecole polytechnique - IN2P3/CNRSCalor Calorimetry optimised for jets Read out scheme for a 64 channel chip Reading the chips through a token ring Cost ~ 0.2 Euros/ch ~ 64 million channels

Henri Videau LLR Ecole polytechnique - IN2P3/CNRSCalor Calorimetry optimised for jets Conclusions Join the worldwide effort of the CALICE collaboration To extract the physics produced in an electron linear collider below 1 TeV, a measurement of the jet energies with a stochastic term at a level of 0.3 or below seems mandatory. Such a precision does not seem out of reach with an adequate calorimetric hardware and a proper software. We have a roadmap with hardware developments and prototypes (2004) and with software imagination