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Fourth Concept Calorimetry IDAG Dan Green Fermilab

Fourth Concept Calorimetry

Jan 27, 2016



Kathy Sander

Fourth Concept Calorimetry. IDAG Dan Green Fermilab. DESY Review. Previous calorimeter review was positive and supportive. Main issues are not technical but managerial. Algebra for Dual Readout. - PowerPoint PPT Presentation
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Page 1: Fourth Concept Calorimetry

Fourth Concept Calorimetry

IDAGDan Green


Page 2: Fourth Concept Calorimetry

DESY Review

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

Page 3: Fourth Concept Calorimetry

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

Page 4: Fourth Concept Calorimetry

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.











Page 5: Fourth Concept Calorimetry

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

















Page 6: Fourth Concept Calorimetry

Fourth Calor - Warsaw

Page 7: Fourth Concept Calorimetry

Fourth @ Warsaw - Linearity

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

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

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Fourth- UIC, Energy ResolutionEnergy resolution achieved is within requirements

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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.)

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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)

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Fourth – UIC, Crystals

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

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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.

Page 14: Fourth Concept Calorimetry

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.

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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









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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.

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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

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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.