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Fourth Concept Calorimetry

IDAGDan Green

Fermilab

DESY Review

Previous calorimeter review was positive and supportive. Main issues are not technical but managerial.

Algebra for Dual Readout• Suppose both Q (quartz) and S (scint) are calibrated

with an e beam, so Q and S are measured in “electron GeV”.

• Suppose h/e is determined by mapping out pion/electron mean over a range of energy.

• Where f = f(E) is the neutral energy fraction of the hadronic cascade. <f> evaluated a la Wigmans or Groom (PDG) – e.g. <f> = 0.11 log(E)

• The aim of dual readout is to simultaneously measure E and f and thus avoid the resolution term due to neutral fluctuations event by event, dE = df(e-h) if the calorimeter is not compensating

)/)(1(/ ehffe

Algebra - II• Measuring the Q and S response and knowing h/e for both Q and

S, event by event E and f can be solved for:

• The result for energy is linear in Q and S and therefore an ensemble of particles, a jet, can be measured and yield the correct energy, without df fluctuations, without the need to separate the energies of the individual hadrons in a jet as is needed in PF algorithms.

)]1)(/[()(

)1/()1(),1/()(

)/(],)/)(1([

)/(],)/)(1([

SQSQf

SQE

ehehffES

ehehffEQ

SS

Algebra - III• On the other hand the result for f is non-linear, so that one gets a

weighted mean for f.

• For example 2 particle overlap in some cell:

)}1]()()/{[(])()[( 2121212112 SSQQSSQQf

481.0

477.0

21.85,45.41,98.15

56.60,2.27,28.9

507.0,43.0,33.0

7.0,2.0

10050

10020

1005020

1005020

1005020

f

f

SSS

QQQ

fff

Fourth Calor - Warsaw

Fourth @ Warsaw - Linearity

Extracting E appears to be good to a few % w.r.t. the mean value.

Fourth UIC - OverallAll fiber baseline. Depth is ~ 7.8 λ. Dual readout with time history (n)

Fourth- UIC, Energy ResolutionEnergy resolution achieved is within requirements

Fourth – UIC, n DetectionThe binding energy fluctuations are determined event by event using the delayed n recoils in the scint fibers. Note the anti-correlation of the n signal with the Q signal (e.m.)

Fourth – UIC, Particle ID

Use S and C signals to separate mu (small energy deposit) and e (more C than S) and pions (mix of S and C)

Fourth – UIC, Crystals

Baseline is fibers. Crystals have advantages. No longitudinal segmentation for redundant measurements.

Results from CMS Test Beams

• For the LHC there have been extensive tests of the calorimetry

• These data allow for the extraction of <fo>, the mean neutral fraction of a hadronic shower as a function of beam momentum for pion momenta between 2 and 300 GeV

• There were TOF and Cerenkov available which made it possible to study responses to pi, K and p at low momenta.

Data on pion/electron Response

This data was taken with a “mip” in the ECAL. The response is purely that of HCAL which is a brass/scintillator sandwich. Note that the data cannot be explained by a single logarithmic behavior for f.

Extraction of the Mean Neutral Fraction

Assuming that for the HCAL, e/h = 1.4 independent of energy, one can extract the average neutral fraction as follows:

Note that e/h=1.4 fits at high energy but fails, <fo> < 0 at low energies - < 10 GeV. If f>0 then pi/e > h/e=0.7

)/1/()//(

)1(

ehehef

eE

hfefE

o

e

oo

Particle Species Dependence

The kaon and proton response is rather different from the pion response. In a single readout calorimeter this limits the resolution. In a dual readout it appears that a different f will be found at the same E for different species.

Depth of 7.8 Int Lengths

Baseline is a fairly deep calorimeter with plastic (S) and quartz (Q) fibers. Depth is sufficient.

Expect single particle resolution of:

Where 35% -> 26% with slow n readout (binding energy losses) using time structure of S signal

%5.1/%35 E

Summary• The particle species dependence should be removed by solving for f

event by event. For example f for pions will be larger than for p because the ‘leading particle’ can be a neutral pion in the former case, but a neutron in the latter.

• Nevertheless, it would be useful to validate that assertion.• There appears to be energy dependence in the e/h ratios which

appears at low energies. It would be useful for the Collaboration to log data below 20 GeV and then re-visit the calibration strategy.

• In situ calibration of the HCAL if there is a crystal ECAL in front should be carefully examined.

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