New Challenges of Hadron Calorimetry

1
New Challenges of Hadron Calorimetry

• PFA technique is presenting several new
  challenges to hadron calorimetry. Many of them
  have been discussed extensively
• One new (to me, at least) aspect use of hadron
  calorimeter to measure neutral hadrons (only)
• These hadrons have typically low energies
• They must be measured individually, rather than
  their summed energy
• They need to be detected/measured with rather
  high efficiency
• Why??

2
The ultimate goal is jet-jet spectroscopy, rather
than single jet energy measurement

• Jet masses represent significant contribution to
  the jet-jet invariant mass (need to quantify!
  Rule of thumb Mj0.1Ej)
• Jet mass determination requires that jet
  particles are measured separately
• Very low energy (in LAB) particles make large
  contribution to the jet mass

3
Calorimeter

• 2 cm steel plates
• 200 planes 10x10 m2
• RPC as an active medium
• 1 x 1 cm2 cells
• GEANT 3.21

4
Detector response to different hadrons

• Response number of hit cells
• 2,5,10,20,50, 100 GeV p, K0L, neutrons and
  anti-neutrons
• Response as a function of energy deposited in the
  calorimeter
• v(p2m2) m for p, neutrons
• v(p2m2) for K0
• v(p2m2) m for anti-neutrons

5
Detector response to different hadrons

• Response to different hadrons is the same (2)
  for pgt50 GeV
• Significant non-linearity of the response over
  the whole range of energies
• Energy mis-measurement if the hadron shower split
  into several pieces
• 5 difference in response between charged and
  neutral hadrons (not neutrons)
• VERY different response to neutrons lt30 GeV

6
How about energy resolution?

• Large constant term in the energy resolution
• 13 for p,K
• 11 for n, ñ
• Quite different resolution below 10 GeV ngtpgtKgtñ

7
Calibration of hadron calorimeter?

• Traditionally calibrate the detector response in
  test beams. Not possible for neutral hadrons.
  Situation aggravated by difference in the
  response and by non-linearity of the response
• Monte Carlo calibration?? Sounds miserable..
• What are the ingredients of the simulation?
• Can we verify the correctness of the simulation
• Data-based calibration? Fit the beam energy as a
  function of the calibration
• Beamstrahlung/ISR
• number, nature and spectrum of neutrals

8
Neutral hadrons multiplicity and spectra

• 1 n, 1 ñ, 2K0L per event
• ltpgt 10 GeV, majority of particles lt5 GeV

9
Contribution of neutral hadrons to jet energy

• Most of the neutral hadrons are confined to a
  relatively narrow range plt5 GeV. Perhaps one can
  ignore all the non-linearities and differences in
  response and absorb them into an effective
  calibration?
• But.. contribution of a hadron to jet energy is
  weighted by the hadron energy. Weighted energy
  distribution is much flatter and extends up to
  30-50 GeV
• Contribution of the calibration error to the
  jet-jet mass resolution needs to be evaluated
• Possible calibration methods need to be studied