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SiD Calorimetry: “Progress” at Snowmass. Ray Frey for the Cal. WG. Goal: Optimize performance (i.e. sensitivity to new physics)... using appropriate technologies

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Sid calorimetry progress at snowmass
SiD Calorimetry: “Progress” at Snowmass

Ray Frey for the Cal. WG

Goal: Optimize performance (i.e. sensitivity to new physics)...

using appropriate technologies

While we tend to focus on jet energy resolution as the metric and PFA’s as the means, we should not forget about other important requirements:

  • Multi-jet final states (not Z→q qbar)

    • With or without beam constraint

  • Leptons

    • including taus

  • Heavy quarks

  • Missing energy/mass

  • Combinations of the above

  • (non-pointing) neutrals

  • And in addition, we need to provide:

    • Charged-particle tracking for decays/non-pointing tracks

    • Bhabha reconstruction in endcaps: acollinearity, E, luminosity

    • far forward e- tags, lum., and hermeticity → new group?

SiD Cal R. Frey

What is the baseline calorimeter
What is the “baseline” calorimeter ?

ECal: Silicon-tungsten, finely segmented, 30 layers

HCal: SS or tungsten with any one of 3 digital (?) techs:

← 15M$/mm

SiD Cal R. Frey

Jose Repond

Segmentation is good
“Segmentation is good”

  • Si/W pixel size:

  • Simulations are using 5x5 mm2

  • prototypes are 16 mm2

  • readout chip: designed for 12 mm2

  • How small can we go?? 2-4 mm2 ?

  • Need a physics argument for small pixels.

  • Can get 300 m photon position resolution -G.Wilson

1.5 x the pad size

Fraction of the photon(s) energy per event , closer to a charged track than some distance

J.-C. Brient


Distance in cm

SiD Cal R. Frey

Hcal response
HCal response

Do we understand HCal response, especially for neutral hadrons ?

  • Issues

  • Is the response linear at low energies?

  • Geant issues: low-E cross sections, cut-off parameter

  • Role of slow neutrons (more in scint.) ?

  • Is the response sufficient (resolution) for the gaseous detectors at low energy?

    • thinner radiator? (2cm→1cm SS) ; tungsten radiator?

    • add hydrogenous or n-sensitive material??

Sample of resolution studies by Lei Xia, ANL:




Projection geometry 7.4mm – 12mm cell size


In general, we aim to optimize the detector with PFA’s based on fully simulated data.

However, we can learn about ECal optimizations using fast MC based on full simulations or data. Examples:

  • Brient charged-photon separation: fast MC based on criterion from data/full MC

  • 2-photon separation: D. Strom, based on data. Can apply to fast MC.



I would like a detector which can examine new physics processes in such detail...

Also use it to obtain excellent jet energy resolution (we hope).

Steve Magill

SiD Cal R. Frey

Full pfas applied to sid
Full PFAs applied to SiD

Neutral hadron contribution – S. Magill

A. Respereza

Note: Z→u,d,s

Pfa s underlying algorithm development
PFA’s: Underlying algorithm development

OK, so we’re not quite “there” yet...


SiD Cal R. Frey

Pfa algorithms contd
PFA algorithms (contd)


  • Full PFA’s under development for SiD:

  • ANL, SLAC – Magill, Graf, Cassell, Kuhlmann

    • H-matrix, track extrapolation, and nearest n’bor had. clust.

  • ANL – Lei Xia – cluster based

  • NIU – Chakraborty, Lima, Zutshi – cluster based

  • Note: these include MIP tracking and cluster/track association algorithms

SiD Cal R. Frey

Pfa outline
PFA outline

Example, from

Lei Xia, ANL

  • Calibration of calorimeter

    • Done

    • Not tuned for clustering algorithm

  • Clustering algorithm

    • Done: hit density driven clustering

    • Not tuned with PFA performance

  • Clustering ID

    • Not done: cheating with MC information

    • Basically just need to distinguish EM and HAD showers

    • Identify shower fragments and merged showers would be a plus

  • Track finding algorithm

    • Not done: cheating with MC information

    • Applied some quality cut (tight/loose)

  • Track-cluster matching

    • Done: ‘helix-swim’ extrapolation, min(hit,track)

    • Not tuned with PFA performance

  • Jet algorithm

    • Not included yet

    • Only studied Z-pole -> qqbar (uds) events

  • Detector mode

    • Only SiDmay05 at this moment

      • Si tracker, Si/W EM calorimeter, RPC DHCAL

SiD Cal R. Frey

Sid calorimeter concluding remarks
SiD Calorimeter – concluding remarks

  • Baseline detector design(s) established

  • Recent items: Highly-segmented ECal: Good ; HCal response: ok??

  • Large effort to develop PFAs to be used to study design parameters

  • First results encouraging

    • but presumably resolution is still algorithm limited

  • To facilitate comparison need to

    • Adhere to baseline design(s)

    • Use lcsim software structure and lcio data

    • Adhere to modular structure when developing code (done)

  • Define basic performance criteria for comparison (sanity checks):

    • Single particle response: linearity and energy resolution as function of energy for different particles

    • Two particle separation: efficiency and purity of hit (energy) assignment as function of distance

      • pion & photon, pion & neutral had, neutral had & photon

    • Particle ID: matrix of generated and reconstructed IDs with single particles

    • Z-pole events: reconstructed jet-jet mass

    • WW events at 500 and 1000 GeV: reconstructed single W mass

SiD Cal R. Frey


  • Wednesday telecons – plan to continue to use these to

    • Understand response/resolution and detector-related issues

    • Forum for PFA developers and reconstruction issues for SiD

  • Need to make significant progress on SiD optimizations by end of the year!

  • To do this we need to keep in close contact within the cal. group and with the other WGs (benchmarking, tracking, ...)

  • Suggestions?

SiD Cal R. Frey