Cantilevers, Conditions Databases and Gauge Couplings

1
Cantilevers, Conditions Databases and Gauge
Couplings
Paul BellManchester HEP Christmas Group
MeetingJanuary 2006

• 1. Hardware ATLAS SCT End-Cap Assembly and
  Integration
• 2. Software ATLAS SCT Offline Software and the
  Conditions Database
• 3. Physics Wgg production Quartic Gauge
  Couplings and the Radiation Zero

2
Activities to Date
2001 2002 2003
2004 2005
PhD, University of Birmingham
Anomalous quartic gauge couplings at OPAL in the
nngg final state ATLAS study of Wgg
production quartic gauge couplings and radiation
zero
System test of the ATLAS barrel SCT
QA testing of the ATLAS SCT end-cap modules
CERN fellowship
SCT offline software, conditions database issues
ATLAS SCT EC assembly integration
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1. ATLAS SCT End-Cap Assembly and
Integration
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1. ATLAS SCT EC Assembly and IntegrationIntroduct
ion ATLAS and the SCT
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1. ATLAS SCT EC Assembly and Integration
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1. ATLAS SCT EC Assembly and Integration
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1. ATLAS SCT EC Assembly and Integration

• Construction
• Four concentric barrels and two end-caps each
  of nine disks
• Tiled with 4088 Si micro-strip modules 988 per
  end-cap
• Physics Role
• Gives four space point measurements per charged
  particle track
• Vital role in momentum, vertex and impact
  parameter measurements inside psuedorapidity
  range of h lt 2.5
• Performance
• Gives transverse momentum resolution of dpT/pT
  0.3 for
• pT 500 GeV
• Binary readout each module has two silicon
  planes with 768 channels per side readout by 12
  FE chips

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1. ATLAS SCT EC Assembly and IntegrationEC
Assembly Liverpool and Nikhef
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1. ATLAS SCT EC Assembly and IntegrationEC
Assembly
Modules-to-disk and disk-to-cylinder taking place
at macro-assembly sites - Nikhef (EC-A) and
Liverpool (EC-C) - ECs shipped to CERN as
complete cylinders of 9 disks from these
sites Nikhef Status - module-to-disk completed
for 7of 9 disks - 6 finished disks have been
tested - disk-to-cylinder completed for disks 7,
8, 9 Liverpool Status - module-to-disk completed
for all disks - all disks inserted to cylinder
and aligned - power tapes ("LMTs') defining the
schedule - disk testing inside cylinder still to
be done Expect shipment to CERN mid-Feb for EC-C
and after mid-March for A
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1. ATLAS SCT EC Assembly and IntegrationEC
Assembly
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1. ATLAS SCT EC Assembly and IntegrationEC-C
Programme at CERN

• 1. Reception testing
• - verify no damage occured in transport, focus on
  thorough checks of cooling circuits
• Approximately 3.5 weeks (till early March)
• 2. Final assembly (addition of thermal
  enclosures)
• - transfer to cantilever beam used for
  integration, assemble thermal enclosure, GS
• Approximately 6.5 weeks (end April)
• 3. Testing inside thermal enclosure
• - re-check cooling circuits, test noise
  peformance of modules now in final environment
• Approximately 3 weeks (mid May)
• 4. Integration with TRT
• - roll TRT over the SCT cylinder to complete ID
  EC
• Approximately 5 weeks (mid June)
• 5. Combined testing
• - move to test area, cable up, perform tests (6
  weeks), uncable, prepare for pit
• Approximately 10 weeks (start Sept.)

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1. ATLAS SCT EC Assembly and IntegrationFinal
Assembly Stage

• EC arrives semi-complete
• Note the TPP frame for reception tests and
  eventual combined tests
• Must be transferred to cantilever stand for
  addition of thermal enclosure
• TRT eventually rolls over the EC held on the beam

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1. ATLAS SCT EC Assembly and IntegrationThe EC
Area in SR1, CERN
Reception, assembly and integration take place
inside the EC area of SR1
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1. ATLAS SCT EC Assembly and IntegrationThe EC
Area in SR1, CERN
Reception, assembly and integration take place
inside the EC area of SR1
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1. ATLAS SCT EC Assembly and IntegrationThe EC
Area in SR1, CERN
Reception, assembly and integration take place
inside the EC area of SR1

• Current status
• First cantilever stand is installed
• Extra floor strenthening has been added
• Stand has been load tested
• DAQ experts continue to develop DAQ code using
  the barrel sector
• Didier and Jo commission the test setups cooling
  and electronics (see Jo's talk)

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1. ATLAS SCT EC Assembly and IntegrationThe EC
Area in SR1, CERN
Space in EC area is limited so we hope to expand
into the barrel area once the SCT barrel is
integrated to the TRT A second cantilver stand
will be installed work on the two end-caps will
be in parallel
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1. ATLAS SCT EC Assembly and IntegrationTesting
After Final Assembly

• Once cylinder is inside its thermal enclosure
• but before integration with TRT, 3 weeks
• allowed for testing
• test functionallity of TE
• (internal humidity, function of
• external heaters...)
• test noise performance of modules
• in close to final environment
• Must be planned for now as we need to make
• sure necessary temporary cooling connections
• are added during assembly of thermal enclosure.

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1. ATLAS SCT EC Assembly and IntegrationIntegrati
on Stage

• Rails are installed on the floor and aligned
  parallel to SCT EC cylinder
• ID trolley with TRT inside is installed on rails
• (Radial clearance is 5mm so may use wires
  passing through inner diameter to align)
• Trolley passes over SCT...

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1. ATLAS SCT EC Assembly and IntegrationIntegrati
on Stage

• Rails are installed on the floor and aligned
  parallel to SCT EC cylinder
• ID trolley with TRT inside is installed on rails
• (Radial clearance is 5mm so may use wires
  passing through inner diameter to align)
• Trolley passes over SCT...

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1. ATLAS SCT EC Assembly and IntegrationIntegrati
on Stage

• Rails are installed on the floor and aligned
  parallel to SCT EC cylinder
• ID trolley with TRT inside is installed on rails
• (Radial clearance is 5mm so may use wires
  passing through inner diameter to align)
• Trolley passes over SCT
• SCT load then transferred from beam to trolley
• Survey stage

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1. ATLAS SCT EC Assembly and IntegrationCombined
Testing
Combined testing takes place in the test area of
SR1 (same for barrel and EC)
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1. ATLAS SCT EC Assembly and IntegrationCombined
Testing
Combined testing takes place in the test area of
SR1 (same for barrel and EC)

• Plan to read out one quadrant through all disks
  (easily enough readout for this, though not for
  whole EC)
• Could envisage with the 6 weeks allowed
• 1. Standalone Verification
• SCT (TRT off) initial verification of function
  of the SCT with TRT present
• usual tests of noise performance 5 days
• TRT verification (with SCT off) similar to above
• TRT will use at least 2/32 of total phi, either
  in 1 or 2 slices 5 days
• 2. SCT-TRT Pseudo-Combined
• SCT tests with TRT powered and not
  triggered/triggered 5 days
• TRT tests with SCT powered and not
  triggered/triggered/pairs of triggers 5 days

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1. ATLAS SCT EC Assembly and IntegrationSummary

• The SCT is part of the ATLAS inner (tracking)
  detector and consists of 4 nested barrels and two
  end caps
• End-caps consisting of 9 disks and 988 modules
  are being assembled in Liverpool (EC-C) and
  Nikhef (EC-A)
• EC-C will be delivered to CERN mid-February
  EC-A in mid-March
• Five stages prior to installation in pit
• 1. Reception testing (focus on cooling circuitry
  electrical functionality)
• 2. Transfer to cantilever beam and assembly of
  thermal enclosure
• 3. Testing inside thermal enclosure (including
  noise performance)
• 4. Integration with TRT
• 5. Combined testing with TRT
• Assembly of two end-caps will proceed largely in
  parallel and current estimates predict EC-C will
  be ready for installation by September

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2. SCT Software and the Conditions Database
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2. SCT Software and the Conditions Data
BaseOverview of SCT Offline Reconstruction
Software
Algorithms in the ATLAS software environment
ATHENA
Data Taking The bytestream converter takes
incoming "raw" data and outputs Raw Data Objects
(RDOs) From the RDOs first make clusters of
hits, then space points combining data from both
sides of a module Finally perform the tracking
(combined with other detectors)
Simulated Data
Digitization
CONDITIONS DB
Simulation Input is Monte Carlo events,
simulated in GEANT4 model of SCT geometry and
material Front-end response to the hits modelled
in a digitization algorithm (SCT_Digitization) RD
Os from the digitization algorithm then passed
through same reconstruction chain.
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2. SCT Software and the Conditions Data BaseRole
of Conditions Data

• The offline reconstruction needs to know
• which readout channel is connected to which
  module
• the precise alignment of the detectors
• which channels are dead or noisy
• Furthermore, for accurate simulation the
  SCT_Digitization algorithm must know, e.g.
• which modules and readout chips on the modules
  are active
• the noise levels within/across the modules
• the threshold settings (binary readout)
• which channels are dead or noisy
• Without these data we are simulating a perfect
  ATLAS, not the ATLAS we have built

BS converter
Tracking
Clusterization
Digitization
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2. SCT Software and the Conditions Data BaseUse
of Conditions Data Base During Commissioning

• In the 2004 CTB run, limited use was made of the
  "Lisbon implementation" of the conditions
  database
• dead and noisy channels found in offline
  monitoring masked in clusterization
• channels masked in the DAQ also masked in
  digitization for accurate simulation
• cabling stored in a text file only 8 modules
• SCT/TRT barrel combined test will take cosmic ray
  data in Feb 2006
• ? want to exercise much fuller use of conditions
  data
• Now using the final version of the database COOL

• So far have implemented
• description of cosmic setup (the 504 barrel
  modules)
• access to all module configuration data in
  digitization (thresholds, chips active, bias
  voltages...)
• implementation of masked channels in
  digitization
• ? now allowing accurate simulation of cosmic
  events....

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2. SCT Software and the Conditions Data
BaseDetails Data in COOL

• COOL Basics
• Data are stored in COOL in folders which contain
  payloads
• The payloads can be integers or floats or
  pointers to data outside of COOL
• Data are stored using the principle of
  "intervals of validity"
• e.g. a bias voltage for a particular detector can
  have some value for a period from (run1, event1)
  to (run2, event2). For a given (run, event) the
  DB returns the valid value.
• SCT Configuration
• For the SCT, in our use of COOL, we are
  currently restricted to configuration data (which
  is a subset of conditions data)
• e.g. threshold is a configuration, but noise is a
  condition
• The SCT configuration is recorded in an xml file
  which is read in by the DAQ at start of a run
  this file contains all cabling information, power
  supply settings and a complete description of all
  modules (in fact, what comes out of the
  production DB from the QA)
• Tool exists (Shaun Roe) to put this into COOL, so
  then its there ready for ATHENA (me) to pull out
  whats needed
• Other people are now looking at putting the
  remaining conditions data to COOL, e.g the
  results of calibration scans (noise values)

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2. SCT Software and the Conditions Data
BaseDetails Reading Data in ATHENA

• Made a "tool" which can be called in the
  digitization algorithm to access the SCT
  configurations stored in COOL
• The tool offers the following methods
• getModuleSn(location(layer, phi, eta))
• - returns the serial number of a module at a
  certain geometrical location
• getModuleData(module_serial_number,
  data_requested)
• - returns the module-level conditions data given
  a serial number, eg, bias voltage
• getChipData(module_serial_number, chip,
  data_requested)
• - returns the chip-level conditions data given a
  serial number and chip number
• With these methods it is possible to access any
  piece of configuration data
• Actual use of the data is currently restricted to
  the masked channels no hits are simulated in
  those channels masked in the DAQ
• (masking has so far been randomly applied at the
  1 level in all simulations)

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2. SCT Software and the Conditions Data
BaseSummary

• ATLAS simulation and reconstruction software all
  runs in the ATLAS software environment ATHENA
• The algorithm SCT_Digitization simulates
  response of the modules to charged particles
• Conditions data is particularly important to
  correctly model the characteristics of the SCT in
  the digitization algorithm if we are to simulate
  the ATLAS we have built
• For the cosmic run, now have the data in COOL
  describing complete configurations of all the 504
  barrel modules in the setup
• - thresholds
• - bias voltages
• - masked channels
• - cabling
• - ....
• A tool has been provided in ATHENA to access
  these data and make them available in
  SCT_Digitization

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3. Wgg Production Gauge Couplings and
Radiation Zero
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3. Wgg ProductionIntroduction Some Physics

• SM electroweak lagrangian

where in the second to last term
Last term arises since generators of the SU(2)L
symmetry do not commute (non-Abelian) ? this is
the origin of the self-couplings in the SM,
giving rise to TGCs WWg, WWZ QGCs WWWW,
WWZZ, WWgg, WWZg
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3. Wgg ProductionQuartic Gauge Couplings

• Studying form and strength of TGC and QGC
  couplings tests whether fundamental interactions
  really are described by non-Abelian SU(2)L
  U(1)Y gauge structure
• In addition, QGCs may "provide a window on the
  mechanism responsible for the spontaneous
  breaking of the electroweak symmetry"
• To conserve unitarity in WW- scattering events
  the SM Higgs exchange diagram must
• conspire with the g/Z exchange diagrams and the
  QGC process

• Self couplings have not been measured precisely
  and are studied using "effective lagrangians"
• - write down the most general allowed lagrangian
  term and put limits on the coefficients.

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3. Wgg ProductionIntroduction to Wgg Production
Wgg production is sensitive to a possible AQGC
vertex of the form WWgg NB this vertex is one
of the allowed in the SM but may receive
anomalous contributions

• In addition to being sensitive to a possible
  AQGC, Wgg production is an interesting process in
  itself
• first sign of triple vector boson production
  (which have small cross-section) due to large
  branching ratio to measurable final states (W?em
  or mn) and low partonic centre-of-mass required
• contains a radiation zero in the SM

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3. Wgg ProductionSignal Simulation

• Monte Carlo has been provided by O. Eboli, Sergio
  Lietti (Sau Paulo)
• Includes all tree level diagrams leading to the
  lngg final state, with l e, m
• ISR, FSR, TGC and SM AQGC term the possible
  AQGC diagram

MC includes anomalous contribution from
lagrangian term where anomalous coupling
parameters b0 and bc 0 in SM ? cross-section
varies quadratically with these parameters MC has
been interfaced to ATLFAST in the ATHENA
environment

• Inclusive as possible set of cuts are applied on
  ATLFAST quantities (no proper trigger study)
• Two photons PTg gt 15 GeV, hg lt2.4
• One electron or muon PTl gt 25 GeV, hl
  lt2.4
• Missing energy PTmissgt 20 GeV
• Separations DRlg gt 0.8, DRgg gt 0.4
• Plus cut on W transverse mass MTW gt 65 GeV
• (removes events where photons come from final
  state charged lepton)

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3. Wgg ProductionSM Background Simulation

• Principal backgrounds to Wgg are expected to
  arise from Wg jet and W 2jet events in which
  one or both jets are mis-identified as a g
• This mis-identification occurs with probability
  1/Rjet where Rjet is the g-jet rejection factor
• Since cross-sections for W(g) events are orders
  of magnitude higher than Wgg, need high jet
  rejection factor if backgrounds are to be
  controlled
• Evaluate the backgrounds as follows
• Generate a large number of Wg jet and W 2jet
  events
• For Wg jet, for each event try the photon with
  every jet relabelled as (i.e., pretend that it
  is) a photon and for each time the event then
  passes the selection, accept it with weight 1/
  Rjet
• For W 2jet, for each event try every jet
  relabelled as a photon with every other jet also
  relabelled as a photon and for each time the
  event passes accept it with wieght (1/ Rjet)2
• Still using Rjet 1300 this needs to be
  optimised

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3. Wgg ProductionATLFAST Distributions
In 30fb-1 (3 years of low luminosity running)
for e and m channels combined - signal
events 42.4 (assuming 80 efficiency for
photons) - background events 35.9 Also fully
simulated 4000 e- events evgen, simulation,
digitization, recon. ? AODs - agreement with
ATLFAST to 10
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3. Wgg ProductionStudying the AQGCs
Transverse energy of highest energy photon, pT,
and invariant mass of photon pair, Mgg, offer
good sensitivity to the AQGC (e- channel only
shown, 30fb-1)
Sensitivity is in high pT region and for high gg
invariant masses (very little SM signal or
background here) Study not complete but first
indications based on maximum likelihood analysis
are limits on b0 around 110-4, an order of
magnitude tighter than the current LEP limits.
pTg
Solid line SM (b0 bc 0) Dashed lines b0
AQGC
Mgg
ATLFAST 10.0.1
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3. Wgg ProductionThe Radiation Zero Theory

• In addition to sensitivity to the quartic gauge
  couplings, the Wgg final state also offers
• the chance to observe a "radiation zero". Theory
• In the SM, the amplitude for qqgWg vanishes for
  cosqW -1/3 where q is the angle between the q
  and the W in the parton CMS
• In the case of two photons, the radiation zero is
  preserved in the limit that the two photons are
  collinear
• A study of the radiation zero in the Wgg case was
  reported in hep-ph/9702364 (1997)
• published in Phys.Rev. D56 by U. Baur et al
• Shown here that radiation zero can be observed as
  a dip in the distribution of
• Dy(gg,W) ygg yW,
• or
• Dy(gg,e) ygg ye
• where ygg, ye and yW are the rapidities of the
  two photon system, the e- and the W
• (considering e- case only)

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3. Wgg ProductionThe Radiation Zero at ATLAS
Events in 30fb-1
ygg - ye
Again, this is only the electron channel, for
30inv fb assuming the MC is correct and the
backgrounds do not grow, the dip should be
observable
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3. Wgg ProductionThe Radiation Zero at the
Tevatron (Baur et al)
Recap theory says that the 2 photons must be
collinear to observe the zero and indeed the dip
can be seen only for cos(q)gg gt 0
from hep-ph/9702364
cos(q)gg
ygg yW
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3. Wgg ProductionRadiation Zero in Wgg at LHC
(Generator Level)

• Using the MC supplied by Eboli,
• obtained unexpected results
• Dip visible across the full range of opening
  angles
• Never anywhere in this range is it very
  pronounced
• Given that this is now pp
• not pp, expected dip to be
• symmetric in Dy ygg ye but
• with similar behaviour wrt the
• photon opening angle as seen
• at Tevatron
• Similar behaviour seen with an
• alternative generator
• ? tried to reproduce Baur's results at generator
  level by modifying Eboli's MC for the LHC to
  simulate Tevatron...

cos(q)gg
ygg yele
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Tevatron Comparison _at_ Generator Level
Left Results from hep-ph/9702364 (photon
opening angle in lab frame) Below Results from
Eboli MC
cos(q)gg
ygg yW
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Tevatron Comparison _at_ Generator Level
Left Results from hep-ph/9702364 (photon
opening angle in lab frame) Below Results from
Eboli MC Below right Results from Eboli MC
boosted to parton centre-of-mass. i.e., the
opening angle of the photons is now in parton
CMS, not the lab. (Rapidity difference same in
both frames)
cos(q)gg
ygg yW
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3. Wgg ProductionRadiation Zero at LHC Revisited

• If I boost the LHC radiation zero plot to the
  parton CMS, the dip becomes much more apparent
• now clearly seen if the opening angle of the
  photons satisifies cos(q) gt 0

cos(q)gg
ygg yele
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3. Wgg ProductionRadiation Zero at LHC Revisited

• If I boost the LHC radiation zero plot to the
  parton CMS, the dip becomes much more apparent
• now clearly seen if the opening angle of the
  photons satisifies cos(q) gt 0
• But, all very well when at generator level but
  of course we will not be able to make this
  transform on the data
• Thus, if what I am showing is true, the
  radiation zero will be more difficult to observe
  than first thought
• Open ended discussion with Eboli and Baur to try
  and understand this

cos(q)gg
ygg yele
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3. Wgg ProductionSummary

• Quartic (and triple) gauge couplings intimitely
  connected to the non-Abelian symmetry of the SM
  and should be measured as closely as possible
• Quartic gauge couplings also connected to Higg's
  sector of SM
• Wgg offers chance to probe WWgg coupling at the
  LHC and is an interesting SM process in itself
  triple vector boson production with radiation
  zero
• I set out to study the QGCs the radiation zero
  should drop out of any Wgg study "for free"
• Unexpected predictions for the radiation zero
  have been obtained
• either an error on my part or a problem with
  either Eboli's or Baur's MC
• trying to resolve this
• Also has been an exercise for me in running full
  ATLAS simulation chain
• Unfortunately very little time permitted in the
  last year