Quarknet Presentation 20022

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Quarknet Presentation 2002-2

• By
• Yasar Onel
• University of Iowa
• Iowa City, IA 52242

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CMS Detector Subsystems
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CMS in the Collision Hall
Tracker ECAL HCAL Magnet Muon
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(No Transcript)
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Calorimetry - I
Electrons, photons and hadrons will be stopped by
the calorimeters allowing their energy to be
measured. The first calorimeter layer is designed
to measure the energies of electrons and photons
with high precision. Since these particles
interact electromagnetically, it is called an
electromagnetic calorimeter (ECAL). The event
display on the right shows a simulation of the
two-photon decay of a 130 GeV Higgs boson in CMS.
The two photons are not seen in the tracker
(inner part) but deposit their energy in the ECAL
(seen as the red "blocks")
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Calorimetry - II
Particles that interact via the strong
interaction, hadrons, deposit most of their
energy in the next layer, the hadronic
calorimeter (HCAL). Neutrinos escape direct
detection but their presence can be inferred as
an apparent energy imbalance in a collision. The
event display on the left shows a simulation of a
180 GeV Higgs boson decaying to two Z bosons,
which in turn decay into two electrons (seen as
red blocks in the ECAL) and two hadronic jets -
seen as blocks in the HCAL
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The physics channel that imposes the strictest
performance requirement for the electromagnetic
calorimeter (ECAL) is the decay of the Higgs
boson with mass in the range 100-140 GeV into two
photons. All the terms making up the energy
resolution (i.e. stochastic, constant and noise)
have to be kept small and should be roughly equal
at photon energies corresponding to approximately
half the Higgs mass.
Calorimetry - III

• The resolution of the energy measurement of the
  electromagnetic calorimeter is driven by three
  major parameters
• The shower containment and photostatictics
• The electronic noise and pileup energy
• The constant term
• The full energy resolution is the sum of these
  terms and is shown in the figure on the left.

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Calorimetry - IV
The performance required from a hadron
calorimeter (HCAL) is less constrained by the
physics processes. The jet energy resolution is
compromised by effects such as the jet-finding
algorithm, the fragmentation process, the
magnetic field and energy pile-up when running at
high luminosity. The important characteristics
are the transverse granularity and the h
coverage.
The energy resolution in the Barrel HCAL for
pions as a function of beam momentum is displayed
for interactions in the HCAL only and in ECAL or
HCAL. The absolute energy scale was set using 50
GeV pions interacting only in the HCAL.
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Calorimetry - V
Measured energy resolution for electrons (upper
figure) and pions (lower figure) for the HF
calorimeter. In the hadronic energy study, the
intrinsic resolution is found to scale with the
logarithm of the energy (squares in the lower
figure).
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EM Calorimeter - I

• -High performance electromagnetic calorimeter
• -Scintillating crystal calorimeter
• -Lead tungstate crystals
• Excellent energy resolution
• 80,000 crystals
• APDs

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EM Calorimeter - II
-The crystals in the barrel have a front face of
about 22x22 mm2 - which matches well the Moliere
radius of 22 mm. -The crystals must have a total
thickness of 26 radiation lengths - corresponding
to a crystal length of only 23 cm. -In the
endcaps the crystals are slightly wider - with
rear faces measuring 30x30mm2
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EM Calorimeter - III
The light monitoring system is designed to inject
light pulses into each crystal to measure the
optical transmission.
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EM Calorimeter - IV
CMS will utilize a preshower detector in the
endcap region (rapidity range 1.65 lt h lt 2.6).
Its main function is to provide g-p0 separation
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EM Calorimeter - V
The scintillation light from the crystals must be
captured by a photodetector, amplified and
digitized. A schematic of the readout sequence is
shown in the figure below
The first element is the PbWO4 crystal, which
converts energy into light. The light is
converted into a photocurrent by the
photodetector. The relatively low light yield of
the crystal necessitates a preamplifier in order
to convert the photocurrent into a voltage
waveform. The signal is then acquired and
digitized. The resulting data are transported off
the detector via optical fiber to the upper-level
readout
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EM Calorimeter - VI
Photodetector (Avalanche Photodiode) principle
Photons convert in the p layer. Photoelectrons
drift towards the abrupt p-n junction where
ionization starts and avalanche breakdown occurs.
The avalanche breakdown results in impact
electron multiplication.
To avoid the design and construction of a very
large quantity of radiation-hard electronics, the
data are transported, immediately after the
digitization step, to the counting room by
fiberoptic links
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EM Calorimeter - VII
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EM Calorimeter - VIII

• The upper level readout has four main functions
• formation of trigger tower energy sums
• pipelining (storing the data until receipt of a
  Level-1 trigger decision)
• transmission of the data from the triggered event
  to the Data Acquisition System
• providing interface functions for the on-detector
  electronics

Layout of the upper-level readout. The optical
receiver deserializes the data from the Very
Front-Ends. The linearizer transforms the
incoming data to a representation which
facilitates analysis by the trigger (e.g.
formation of energy sums) without further
conversions
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Hadronic Calorimetry - I
-Identification and measurement of quarks,
gluons, and neutrinos-Measuring the energy and
direction of jets and of missing transverse
energy flow in events. -h5 -identification
of electrons, photons and muons as well.
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The hadron barrel (HB) and hadron endcap (HE)
calorimeters are sampling calorimeters with 50 mm
thick copper absorber plates interleaved with 4
mm thick scintillator sheets.
Hadronic Calorimetry - II
Copper has been selected as the absorber material
because of its density. The HB is constructed of
two half-barrels each of 4.3 meter length. The HE
consists of two large structures, situated at
each end of the barrel detector and within the
region of high magnetic field. Because the barrel
HCAL inside the coil is not sufficiently thick to
contain all the energy of high energy showers,
additional scintillation layers (HOB) are placed
just outside the magnet coil. The full depth of
the combined HB and HOB detectors is
approximately 11 absorption lengths.
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Hadronic Calorimetry - III
Light emission from the tiles is in the
blue-violet, with wavelength in the range l
410-425 nm. This light is absorbed by the
waveshifting fibers which fluoresce in the green
at l 490 nm. The green, waveshifted light is
conveyed via clear fiber waveguides to connectors
at the ends of the megatiles.
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Hadronic Calorimetry - IV
Megatiles are large sheets of plastic
scintillator which are subdivided into component
scintillator tiles, of size Dh x Df 0.87 x 0.87
to provide for reconstruction of hadronic
showers. Scintillation signals from the megatiles
are detected using waveshifting fibers. The fiber
diameter is just under 1 mm.
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HPD
Hybrid PhotoDiode mates photocathode to Si diode
(pixels) array. There is a 12kV drop. If E and
B are parallel, works in 4 T CMS field.
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RBX Readout Module

• The readout module (RM) integrates the HPD, front
  end electronics, and digital optical drivers. PRR
  passed March 1-2.

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HE - Full Assembly
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HB SX5
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(No Transcript)
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Why HF?

• Covers the pseudorapidity range 3-5
• HF psedorapidity range 4.5-5 will get
  100Mrad/year. Therefore the detector should be
  able to withstand this exceptionally high
  radiation field.
• Two main objectives
• To improve the measurement of the missing
  transverse energy EmissT
• To enable identification and reconstruction of
  very forward jets

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Experimental Technique

• Light is generated by Cherenkov effect in quartz
  fibers
• Sensitive to relativistic charged particles
  (Compton electrons...)
• d2N/dxdl2paz2(sin2q/l2)
• (2paz2/ l2 )1-1/b2n2
• bmin 1/n
• Emin 200 keV
• Amount of collected light depends on the angle
  between the particle path and the fiber axis

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HF PPP1 Side View
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HF Fiber Spacing (PPP1)
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Response to Electrons and Pions

• HF PPP1 responds linearly within 1 to electrons
  in the energy range tested (6 200 GeV). The
  pion (neg) response is highly nonlinear.

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Electromagnetic Energy Resolution
137/sqrt(E) with 1.6 fiber packing Fraction
(HAD95)

• Electromagnetic energy resolution is completely
  dominated by photostatistics (Np.e.). The usual
  parametrization, a/sqrt(E) b, results in a192
  and b9 for the PPP1. 0.85 fiber fraction
  degrades the EM energy resolution by a sqrt(2)
  compared to HAD95 (1.6).

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Fiber Radiation Damage and Induced Resolution
54 Mrad QP

• Quartz fiber irradiation studies have been
  carried out in the last several years. The
  induced attenuation profile shows that there is
  less absorbtion in 400-500 nm (PMT) region
  compared to either shorter or longer wavelengths.

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HF Fiber
QP (Quartz, Plastic) Fused silica core, polymer
cladding, UV-cured acrylate buffer. 850 km for
600 core N.A. 0.33 /- 0.02

• QQ (Quartz, Quartz)
• Fused silica core, fluorine-doped silicate
  cladding, polyimide buffer.
• 100 km for 600 core
• N.A. 0.22 /- 0.02

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FLUKA Calculations

• Recent radiation background simulations show
  improvement in the design of the shielding around
  the PMT region by a factor of two. There is no
  issue with the radiation dose or neutron flux
  where the PMTs are located.
• All neutrons 2.54x1012
• Neutrons (Egt100KeV) 1.63x1012
• Neutrons (Egt20 MeV) 5.12x1011
• Ch. Hadrons 2.26x1010
• Muons 4.65x109
• Photons 1.53x1012
• Dose 7 krad

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HF - Mechanics Wedge Concept
PMT Plate
Ferrule Plate
Strong Back
Air-core Light Guides
20-degree Steel Wedge
Borated (Pb) Polyethylene
Fibers Source Tubes

• The concept wedge allows for a simpler
  construction scenario. Each 20-degree sector is
  optically and electrically independent. This
  makes manufacturing, quality control and testing
  more streamlined.

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Mechanics HF Wedge Structure

• 20-degree sectors will be made from machined
  square bricks to conform to 20-degree wedge.
• Mechanical assembly is straight forward two
  independent studies found no fundamental problems
  with this construction technique.
• The optical assembly (bundles and ferrules) is
  easier.
• It lends itself better for multiplexed fiber
  insertion operation at different stations and
  20-degree wedge is the smallest unit for
  insertion operation.
• Source tube placement in the tower centers is
  easier.

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HF Wedge and Optical Assembly

• HF 20-degree sectors will be assembled into a
  superstructure with the aid of two L-shaped
  lifting fixtures. Each sector is optically and
  electronically independent.

The routing of the fibers and source tubes are
designed and being tested on the PPPWedge this
month (February 2001).
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HF READOUT BOX OPTICS DESIGN
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First 2 HF Wedges in Superstructure

• The wedges will be bolted onto the superstructure
  for support and it also serves as a part of the
  steel shielding.

Steel Superstructure
Readout Boxes
20-degree HF Wedge
Back-plane
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½ HF in Superstructure
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Assembled HF

• The HF will rest on a transporter table that
  enables motion to clear the beam pipe during
  installation and maintenance.

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HF Design Parameters Update (Sept 2000)

• The HF fiber matrix is optimized for the required
  performance and ease of optical assembly. Two
  independent simulation studies indicate that the
  fiber spacing can be coarsened without much
  degradation in performance.
• Fiber Spacing
• 5 mm x 5 mm square grid (from 2.5 mm x 2.5 mm)
• Quartz fiber packing fraction
• 0.85 ( 600-micron core dia.)
• Fiber OD 800-micron dia.
• The fiber hole/groove max OD 900-micron
• Dead region between wedges
• 5 mm or less between fibers of neighbor wedges
• No change in
• h x f segmentation (0.175 x 0.175)
• 165 cm (EM), 143 cm (HAD)
• Diffusion welded grooved steel plates

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HCAL - ? Coverage
(A.Nikitenko)
HF needed for tag jets, missing ET and jet vetoes
(SUSY)
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Higgs Discovery Reach
The WW fusion process, isolated by 2 tag jets
with formation of the Higgs and subsequent decay
into W W may be THE discovery mode for Higgs
masses lt 200 GeV.
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Tag Jets in WW -gt 2lv
M 130, 160, 190,
115 GeV
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Higgs Discovery Limits
The main final state is ZZ --gt 4l. At high masses
larger branching ratios are needed. At lower
masses the ZZ and ??? final states are
used. LEP II will set a limit 110 GeV. CMS will
cover the full range from LEPII to 1 TeV.
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HCAL Electronics - Overview
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Calibration Tools
E) Test beam - normalization between GeV vs. ADC
vs. A,B,C,D - ratios elec/pion, muon/pion -
before assembly a few wedges, 2002 F) Physics
events - mip signal, link to HO muon - calo
energy scale (e/pi) charged hadron - physics
energy scale photonjet balancing Zjet
balancing di-jets balancing di-jet mass W-gtjj in
top decay gtgt non-linear response gtgt pile-up
effect
A) Megatile scanner - Co60 gamma source - each
tile light yield - during construction all tiles
and fibers (HF) B) Moving radio active source -
Co60 gamma source - full chain gain - during
CMS-open (manual) all tiles and fibers (HF) -
during off beam time (remote) tiles in layer 0
9, all fibers C) UV Laser - full chain timing,
gain-change - during off beam time tiles in layer
0 9, all fibers all RBX D) Blue LED - timing,
gain change - during the off beam time all RBX
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HCAL DCS

• HV power supply monitoring
• LV power supplies monitoring
• LV tº on-board monitoring
• Source calibration
• Laser calibration
• LED calibration
• Parameter downloading

LV1
Laser
HV

Source motor drivers
RBX parameters DB
HV
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CMS_HF For Heavy Ion Physics

• Heavy quarkonium, hard jet and high-mass dimuon
  production.
• Impact parameter determination since forward
  rapidity region is free of final state
  interactions.
• Insensitivity of the forward rapidity region to
  details of the nuclear collision dynamics, HF can
  be used for the fast selection of inelastic
  nucleus-nucleus collisions.
• Non-statistical fluctuations of the rad/em energy
  reaction in the forward rapidity region could be
  quartz matter fireball formation??
• Forward energy region contains the most energetic
  reaction products.