CALOR2002. The Future of Calorimetry In High Energy Physics Dan Green Fermilab. Outline. Introduction Status Improvements in Detectors Non-compensation “constant term” Mixed Media Energy Flow Missing E T Intrinsic Limitations Transverse Position Leakage and Depth Signal Speed
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The Future of Calorimetry
In High Energy Physics
in “ECAL” + HCAL. Particle ID uses differences in Xo and (e,) and in radiation cross section (e, ).
At some point the muon becomes much harder to identify as an object that “only ionizes”.
Jet energy error is ~ single particle error, if the only error is energy measurement.
Dijet mass error is determined by jet error
Missing energy error is also determined by single particle error.
With fine sampling, W << 1, and small source capacity (accordion) precision , high speed, EM calorimetry is possible.
e.g. PbWO4 – CMS
Fully active devices have no sampling
fluctuations. However, there is
noise and photon statistics, and light
dE/E ~ 0.7 % at 100 GeV
even though stochastic
coefficient is only ~ 2.3 %
Non-compensation leads to dE/E which decreases as ln(E).
As energy increases fo -> 1 and effect of e/h is reduced. At very high energy non-compensation is not an issue.
Limited at the LHC by pileup causing id errors due to the intrinsic size of a hadron shower ~ .
For present energy scales at the LHC and LC use tracker energy measurement if possible. At a VLHC this will not help.
radius 0.9 has
~ 400 towers
of HCAL and
~ 10,000 towers
of ECAL in CMS.
is sparse -> can
identify tracks with
HCAL lego shown.
Mean 81.7 GeV, (21%) Mean 105.5 GeV, (17%)
Missing ET is a global variable. There is a 16% improvement in the missing ET significance using energy flow (no pileup). Data set is badly mismeasured high Et dijets.
Tesla ECAL study – fine grained.
dx ~ Xo * a /E
d ~ dx/R.
EM shower angle limited by stochastic shower fluctuations.
the number of
“particles” in a
jet, especially the
dense “core” of
a jet. Limits set
to “energy flow”
Good hadron energy measurements will require a depth > 10 due to late developing shower leakage and fluctuations .
There is a finite probability of a single hadron to “leak” a large fraction of its’ energy.
With g splitting and with pion decays, depths > 10 are not useful.
Jets “leak” too – 0.1 % will lose > ½ of the energy due to splitting.
# Jets with energy > Missing ET
The jet splitting creates a SUSY background. Cutting on angle is not very incisive.
LHC calorimetry is fast enough to minimize pileup effects.
Calorimeter signals at LHC is ~ contained in 1-2 bunching crossings.
Si Diode E field
10 kV h
FSR is the biggest effect. The underlying event is the second largest error (if cone R ~ 0.7). Calorimeter resolution is a minor effect.
n.b. no FSR here, so dM/M ~ 9% for “boosted” Z. Pileup is not the dominant effect.
dijets in CMS with and
without FSR. The
dominant effect of FSR
rms rises from
~ 11% to ~ 19%, the
distribution shifts to
smaller M/Mo, and a
radiative low mass tail
This technology will not survive in the endcap HCAL if the LHC L increases (independent of C.M. energy).
At high s, the proton can radiate photons. With 2 very small angle recoil tags, 2 photon physics can be studied in a p-p machine. New detectors needed?
LEP are down
by large factors.
L is needed – e.g.
requires a very
dM/M ~ 3%
dE/E ~ 18%/E for jets. This is to be compared to ~ 60% at the LHC.
Only minor EF improvements in missing ET. FSR is soft at wide angles
elastic recoils, scale
~ 10 keV and 10-8 pb
If next generation is successful, many SUSY points will be covered. Complements HEP searches.
V Q I
searched for at
LHC and LC.
n.b. – SUSY is a dark matter candidate giving correct relic abundance since annihilation is weak. Favors light SUSY.