Argonne National Laboratory · Photons 25 % ECAL with 15%/√E 0.072 E jet Neutral Hadrons 10 % ECAL + HCAL with 50%/√E 0.162 E jet Confusion If goal is to achieve a resolution

José RepondArgonne National Laboratory

: Calorimetry reinvented

Colloquium at Georgia State UniversityAtlanta, GA

October 10, 2017

J.Repond: Calorimetry reinvented

2

Particle physics studies the nature of particles that are the constituents of what is usually referred to as matter (wikipedia)

These studies often involve the collision of stable particles (protons, electrons) at high energy, producing events with (more, many, new) particles

Examples of colliders: LHC, ILC, Tevatron, HERA, LEP, EIC…

Particle detectors detect the long-lived particles emanating from these collisions:

Charged: p, K±, π±, μ±, e±, Neutral: γ, n, KL0, ν


3

Particle Detectors contain a number of subsystems

- Vertex detector → measurement of tracks close to interaction point → measurement of secondary vertices (KS

0…)→ measurement of track impact parameters (charm, beauty)

- Inner tracking detector → measurement of charged tracks and their curvature (momentum) - Calorimeter → measurement of the energy of particles (destroys the particles) - Solenoid → provides magnetic field to bend tracks depending on their momentum - Muon chambers → identify tracks which punched through the calorimeter unharmed

…most colliding beam detectors look more or less like this one

destructive

4

Why do Jet Physics?

High energy particle colliders produce

Collimated jets of hadronic particles

Given an appropriate algorithm, particles in events can be associated to jets

parto

n

{p1, p2, … pn} → {J1, J2, … JN}

with n » N

Use jets to reconstruct momentum of partons study short distance QCD heavy particles decaying into qq, e.g. W±, Z0

Jets can be associated with partons ofunderlying hard scattering

5

2 Examples of measurements with jets

Dijet in photoproduction at HERA

→ reconstruction of the fraction of photon energy participating in the hard scattering

Dijet production in deep inelastic scattering at HERA

→ reconstruction of the fraction of the proton momentum taken by the interacting parton

e

jetT

jetTobs

yE

eEeEx

jetjet

2

22

11

)1(2

2

Q

Mx jjBj


6

Electromagnetic Showers IInitiated in matter by incident photons or electrons (positrons)

Dominant processes

Electrons → bremsstrahlung (emission of a photon, when subject to deflection from original trajectory)

Photons → pair production (creation of electron-positron pair in the

electric field of nuclei)


7

Electromagnetic Showers II

Interplay of bremsstrahlung and pair production

Leads to the development of a shower of particles

Sandwich calorimeter

Most widely used calorimeter concept in HEP Absorber plates interleaved with active sensors (e.g. scintillators) Absorber plates incite the particles to shower Active sensors measure particles through the ionization process

Particle Ab

so

rber

Act

ive

Shower in a calorimeter

Similar process for hadrons →hadronic showers

charqediparticle NE


8

EM and HAD Response in Calorimeters

Typical calorimetric response

To hadrons and electrons of same energy different

e.g. Evis(20 GeV e–)/Evis(20 GeV π–) ~ 1.6 in CDF

Hadronic showers in calorimeters

Have an electromagnetic and a hadronic component The fraction of these components fluctuate from shower to shower Plus, the response to em and hadronic component different (also within a single shower)

Poor resolution for hadronic showers

π- e-

ATLAS Forward calorimeter


9

Solution → Compensation

Equalize the response to e– and π– (of same energy) e/π ~ 1 Can be done with e.g. Uranium and scintillator sandwich calorimeters ZEUS: Thickness of scintillator tuned to provide e/π ~ 1

Hadronic jets of particles produced at colliders

Mixture of charged, neutral hadrons and photons How to optimize their energy resolution?

ZEUS

30 GeV electrons and pions

World’s best single hadron energy resolution for a colliding beam experiment

10

Trend in Calorimetry

Tower geometry

Energy is integrated over large calorimeter volumes into single channels

Readout typically with high resolution (> 10 bits/channel)

Individual particles in a hadronic jet not resolved

ET

Imaging calorimetry

Large number of calorimeter readout channels (~107)

Option to minimize resolution on individual channels (1, 2… bits/channel)

Particles in a jet are measured individually


11

Advantages of Imaging CalorimetryParticle ID

Electrons, muons, hadrons → (almost) trivial

Software compensation

Typical calorimeters have e/h ≠ 1 Weighting of individual sub-showers possible → significant improvement in σE

had

Leakage corrections

Use longitudinal shower information to compensate for leakage → significant improvement in σE

had

Measure momentum of charged particles exiting calorimeter

Application of Particle Flow Algorithms (PFAs)

Use PFAs to reconstruct the energy of hadronic jets


12

Particle Flow AlgorithmsAttempt to measure the energy/momentum of each particle in a hadronic jet with the detector subsystem providing the best resolution

Particles in jets

Fraction of energy

Measured with Resolution [σ2]

Charged 65 % Tracker Negligible

Photons 25 % ECAL with 15%/√E 0.072 Ejet

Neutral Hadrons

10 % ECAL + HCAL with 50%/√E

0.162 Ejet

Confusion If goal is to achieve a resolution of 30%/√E →

≤ 0.242 Ejet

ECAL

HCAL

γ π+

KL

PANDORA PFA based on ILD detector concept


Factor ~2 better jet energy resolution than previously achieved

18%/√E

13

Application of PFAs

Past

Pioneered by ALEPH

Used by ZEUS, CDF…

Present

CMS

Future

ILC/CLIC detectors CMS endcaps ALICE forward Any new colliding beam detector

Detectors optimized for PFAs


● Calorimeter needs to be optimized for photons: separation into ECAL + HCAL ● Calorimeters need to be placed inside the coil (to preserve resolution) ● To minimize the lateral size of showers, the RMolière of the ECAL needs to minimized ● The segmentation of the readout needs to be maximized ● The active layer or the depth of the E+HCAL needs to be minimized (cost) ● The front-end readout electronics needs to be embedded into the calorimeter

The role of the HCAL reduced to measure the part of showers from neutral hadrons leaking from the ECAL

Two performance measures of a calorimeter optimized for PFAs

J. Repond - Imaging Calorimeters

14

Energy resolution for Identification of energy depositssingle neutral particles (minimize confusion)

PFA Implications for Calorimetry

15

CollaborationGoal

Development and study of finely segmented/imaging calorimeters Initially focused on the ILC/CLIC needs Now widening to include the developments of all imaging calorimeter

Large prototypes built and tested to date

Silicon-W ECAL, Scintillator-W ECAL, Scintillator-Fe/W HCAL, RPC-Fe/W HCAL, RPC-Fe HCAL

4 continents

20 countries

60 institutes

364 physicists/engineers

2nd largest R&D collaboration in HEP


16

Electromagnetic CalorimetersRole

Precision measurement (position, energy) of photons

Absorber

Tungsten (alloy) -> small Molière radius = 3.5 mm Other possible absorbers not considered Depth about 20 X0, to minimize leakage into HCAL

Active media

Silicon pads (1 x 1 cm2 -> 0.25 x 0.25 cm2, 0.13 cm2) Scintillator strips with SiPM readout (45 x 10 mm2) MAPS (30 x 30 μm2 + digital readout) -> DECAL

Prototypes constructed and tested

CALICE Si-W ECAL (10k channels) SiD Si-W ECAL (10k channels) CALICE Scintillator-W (2k channels) ALICE FoCAL (39M channels)


17

How to test a calorimeter?

1) Linearity of the response

Ensures that

Important in traditional calorimeters Not so important in imaging calorimeters (as individual showers are being measured)

2) Resolution of the response to single particles

Typically fitted to

Constant term: non-uniformities, calibration…

Stochastic term: statistics, sampling…

Noise term: independent of energy

Don’t use

CEE

n

EE

CEE

E

)2/2/()( GeVNNEGeVNE visvis

J. Repond - Imaging Calorimetry

18

Monte Carlo Simulations: GEANT4

Electromagnetic shower simulation

Reproduces results at the < 1 % level Multiple scattering still challenging Excellent tool to validate our understanding of the detector

Hadronic shower simulation

Greatly improved in the last few years Precision better than 10% (shapes < 20%) Choice of different models combined into various Physics lists

Adequate simulations are aprerequisite for understanding

the physics of a new technology

Linear within ±1% up to 45 GeV Resolution adequate

-> Negligible contribution to σ(Ejet) Excellent agreement with GEANT4 simulation

19

CALICE Silicon-Tungsten ECAL

Both concept and technical implementation validated

%1.01.1)(

1.06.16

GeVEEE

Linear within ±1% up to 32 GeVResolution quite good

-> Negligible contribution to σ(Ejet)Excellent agreement with simulation

20

CALICE Scintillator-Tungsten ECAL


%1.1)(

4.06.12 6.07.0

GeVEE

E

21

ALICE Forward Calorimeter Upgrade

The ultimate digital calorimeter

Pixels of 30 x 30 μm2 area Total of 39 million channels 1-bit readout -> digital Energy reconstructed as function of number of hits

Granularity particularly important in forward direction

244 GeV electronLayer 4 Layer 8 Layer 12

Response surprisingly linear up to 244 GeV

Resolution not overwhelming

%23)(

430

)(

6

GeVEGeVEEE

22

Hadronic CalorimetersRole

Measurement of neutral hadrons (n, KL0)

Absorber

Steel preferred Tungsten was also explored More compact calorimeter (reduces cost) Degraded resolution (absorption of em component)

Active media

Scintillator pads (3 x 3 cm2) Resistive Plate Chambers (1 x 1 cm2) GEMs, Micromegas (1 x 1 cm2)

Readout

Scintillator -> 14-bit = analog Gaseous -> 1-bit = digital

Large prototypes constructed and tested

CALICE AHCAL(8k channels) CALICE DHCAL (500k channels) CALICE SDHCAL (400k channels)

23

Pions between 8 and 80 GeV/c

Software compensation

Based on energy density weights Improves both linearity and resolution

CALICE Scintillator-Steel HCAL


24

CALICE RPC-Steel HCAL – the DHCALEnergy reconstruction

To first order E proportional Nhit Response saturates (due to finite pad size) Response fitted to a power law Nhit = aEb+c Energy reconstructed as

-> Linear response within ±2%

Energy resolution

Not as good as the AHCAL Levels out at high energies (not a concern!) Can be improved with software compensation techniques

Offers an order of magnitude more granularity than AHCAL


b hitrec a

cNE

%1.03.10)(

1.04.51

GeVEEE

J. Repond - Imaging Calorimeters

25

Timing measurements

Measurement of shower timings using

Scintillator pads or RPC with pads

Positioned downstream of

Steel stack or Tungsten stack

Comparison with hadron shower models

Average 60 GeV shower in 4D

Use reconstructed interaction point in AHCAL/DHCAL

The power of imaging calorimeters

26

Electron-Ion Collider EICPolarized ep, eA collider

√s = 35 – 180 GeV Luminosity = 1034 cm-2s-1

Two possible sites

Brookhaven -> eRHIC Jefferson lab -> JLEIC

Scientific goals

Study of perturbative & non-perturbative QCD Tomography (including transverse dimension) of the nucleon, nuclei Understanding the nucleon spin Discovery of gluon saturation… Construction to start in 2025

Community optimistic about prospect of realization


27

Quantum Chromodynamics QCD

Theory of hadronic interactions (no doubts!)

Has been validated in countless experiments (LEP, HERA, Tevatron, LHC…) where perturbative calculations are possible (high energy -> small coupling)

A deeper understanding of QCD requires exploring

The non-perturbative regime of the theory

3D tomography of the nucleon and nuclei

Generalized Parton Distributions (GPDs) Transverse Momentum Distributions (TMDs)

Contributions to the nucleonic spin Confinement Nuclear modifications of the parton density functions Non-linear evolution (saturation) ….

These are currently all open questions


28

Measurements at the EICPhysical quantity Process Measurement

challenges

Structure functions F2, FL

Nuclear structure functionsInclusive scattering Electron identification,

background rejection, luminosity

Spin structure functions Inclusive scattering + polarization

Gluon density Charm,dijet production…

Secondary vertex, pion/kaon separation, hadronic jets

Generalized PartonDistributions GPDs

Deeply VirtualCompton Scattering

Forward proton,background rejection

Transverse MomentumDistributions TMDs

Semi-inclusive DeepInelastic Scattering

Pion/kaon separation

Nuclear PDFs Scattering on nuclei Nuclear fragments

Many more

J. Repond - Imaging Calorimetry29

Requirements for EIC Detectors

Vertexing

Event vertex, secondary vertices, track impact parameter

Electron identification and measurement

-4 < η < 4

Hadronic jet measurement

Excellent energy resolution (kinematic reconstruction)

Pion/kaon/proton separation

For most of the solid angle identification needed for p < 7 GeV/c In forward direction needed for p < 50 GeV/c

Forward proton

Large acceptance for momenta up to almost beam energy

Forward neutron

Excellent energy and angle measurement

Vertex detector

Central tracker

Calorimeter

TOF or Cerenkov

Roman pots

00 calorimeter

PolarimeterLuminosity measurement


30

4 Detector Concepts for the EIC

Jefferson lab concept

sPhenix -> ePhenix Argonne concept: SiEIC

Brookhaven concept: BEASTPHENIX#Y>#ePHENIX#Path#

4#4#

By ~2025

By ~2020

ePHENIX

PHENIX sPHENIX

Evolve sPHENIX (pp and HI detector) to ePHENIX (DIS detector)

! To utilize e and p (A) beams at eRHIC with e-energy up to 15 GeV and p(A)-energy up to 250 GeV (100 GeV/n)

! e, p, He3 polarized

! Stage-1 luminosity ~1033 cm-2 s-1 (~1fb-1 /month)


31

The SiEIC Concept

Optimized for Particle Flow Algorithms (PFAs)

Measure each particle individually with the system providing the best E/p resolution

Based on the SiD concept

Originally developed for the ILC High precision silicon tracker (5 vertex + 5 outer layers) Calorimeters with extremely fine segmentation (Silicon, RPCs)

In general

Hermetic enclosure of interaction region Concept not yet optimized for the EIC environment Reduced magnetic field (5 –> 2.5 T) Reduced depths of calorimeters Longer barrel (increased forward detection)

Optimal detector means maximum use of luminosity

32

The 5D Concept

Particle identification ( π – K – proton separation)

Important at the Electron-Ion Collider (EIC) Particle momenta < 10 GeV/c for most of the solid angle Time – of – flight with 10 ps resolution would do the job

The 5D concept

Measure (E,x,y,z,t) for every hit in tracker + calorimeter Requires ultra-fast silicon sensors Eliminates the need for additional PID detectors for most of the solid angle

Ultra-fast Silicon Sensors

Currently being developed based on the LGAD technology Best timing resolution about 27 ps Further improvements ongoing Interest in developing ultra-fast CMOS sensors (addition of amplification layer)

arXiv:1608:08681

Event generation

Produce the simulation input events

Detector simulation

Particle transport through detectors

Digitization

Turn energy deposits in active media into detector hits

Reconstruction of

Event vertex, charged tracks, Particle Flow Objects (PFO)

Perform analysis

Collection of benchmark analyses

33

Full simulation and reconstruction chain

Tools

HepSim

GEANT4 DD4Hep

LCSim

LCSim

Root scripts

Dat

a M

od

el

34

Simulation Studies

Single Particle Resolutions

Generated photons with 1 – 30 GeV Spread over most of solid angle

Determination of TOF Requirement

Using timing information in tracker and ECAL For each track fit time versus path length

Photon energy resolution

TOF PID using silicon with 10 ps resolution

Reconstruction of the F2 Structure Function

Use MSTW PDF to generate DIS events Use CTEQ PDF to correct for acceptance (problem with CTEQ phase space) Validation of entire simulation too chain

Comparison of true and reconstructed F2

35

Electron Method

Results

works quite well in general -> In particular for Q2

and at low-x

Poor resolution

at large-x or small-y (here other methods are better)


36

Conclusions

Trend towards imaging calorimeters for future applications

leading the development of such devices

Various technologies for imaging calorimetry have been validated Further R&D remains to be done

3/4 LHC experiments have adopted or are considering adopting CALICE technologies for their calorimeter upgrades

Argonne is developing a concept of a multipurpose 5D detector for the EIC

J.Repond: Calorimetry reinvented37

Backup Slides


38

Calorimetry for HEP Colliders at Argonne

HRS (PEP)ZEUS (HERA)

ATLAS (LHC)

DHCAL (ILC/CLIC)

Documents

Argonne National Laboratory · Photons 25 % ECAL with 15%/√E 0.072 E jet Neutral Hadrons 10 % ECAL + HCAL with 50%/√E 0.162 E jet Confusion If goal is to achieve a resolution