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Better tower granularity might be needed due to pileup and 'fake' jets. ... Bunch crossing ID can be extended to 12.5 nsec ( 80 MHz) as established in test beam. ... – PowerPoint PPT presentation

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Title: Super LHC SLHC

Super LHC - SLHC
LHC Detector Upgrade Dan Green Fermilab
  • Physics Basics
  • Z vs
  • Rapidity Range
  • Minbias
  • Pileup and Jets
  • Occupancy and Radiation Dose
  • Tracker Upgrade
  • Calorimetry
  • Muons
  • Trigger and DAQ

CERN-TH/2002-078 Physics Potential and
Experimental Challenges of the LHC Luminosity
Upgrade 10x will be challenging!
Mass Reach and L
  • The number of Z detected in leptonic decays is
  • For , if N
    100 is discovery level then M 5.3 TeV is the
    mass reach in 1 year (M4 -gt 5.3 TeV).
  • The leptons will be sharply limited to low y or
    large angles (barrel).

Mass Reach vs L
VLHC LHC Tevatron
In general mass reach is increased by 1.5 TeV
for Z, heavy SUSY squarks or gluinos or extra
dimension mass scales. A 20 measurement of the
HHH coupling is possible for Higgs masses lt 200
GeV. However, to realize these improvements we
need to maintain the capabilities of the LHC
5 TeV
1 TeV
Heavy States decay at wide angles. For example Z
of 1 and 5 TeV decaying into light pairs.
Therefore, for these states we will concentrate
on wide angle detectors.
Inclusive Interactions
  • The inclusive p-p interaction has an inelastic,
    non-diffractive cross section 50 mb.
  • It produces equal numbers of
    which are distributed uniform in rapidity, y,
    with a density 9
    pions per unit of y.
  • The pions have a distribution in transverse
    momentum with a mean, 0.6 GeV.

Detector Environment
Bunch spacing reduced 2x. Interactions/crossing
increased 5 x. Pileup noise increased by 2.2x if
crossings are time resolvable.
Pileup and Luminosity
  • For 50 mb, and 6 charged pions/unit
    of y with a luminosity
  • and a crossing time of 12.5 nsec
  • In a cone of radius 0.5 there are 70 pions,
    or 42 GeV of transverse momentum per crossing.
    This makes low Et jet triggering and
    reconstruction difficult.

Z(120) at L/5 and L
Jet cone and 90 degrees to cone in ?
Log(z), z k/ET
Z(120) Mass Resolution
Note that the calorimeter cells are still fairly
sparsely populated (granularity

) at 1034 . With the cuts shown, the
dM/M with Gaussian fits is the same at L/5 and at
L. Use the fact that QCD implies that there is a
core of the jet at small dR and large z. Extend
to 10x L using tracker and energy flow inside the
jet? If x-ing is time resolvable, pileup is
only 5x. Tracker can be used (energy flow) to
remove charged energy deposits from vertices
within the x-ing which are not of interest.
Tracker and Energy Flow
  • For 120 GeV Z match tracks in ? and ? to
    hadronic clusters within the jet. Improves
    dijet mass resolution. Units are HCAL tower
    sizes. Also use track match to remove charged
    pion deposits from pileup vertices ?

WW Fusion and Tag Jets
Pileup, R0.5, y3
These jets have and ltygt 3. Lose 5x in fake
rejection. We must use the energy flow inside a
jet cone to further reduce the fake jets due to
pileup ( uniform in R).
WW fusion
SLHC Detector Performance
  • Tracking and b-tagging
  • Isolated high pT (gt 20 GeV) tracks - it should
    be possible to maintain similar efficiency and
    momentum resolution
  • without a tracker upgrade, for fixed b-tagging
    efficiency, rejection against light quarks will
    deteriorate by factor 8 (pT 50 GeV)
  • Electron identification and measurement
  • For electron efficiency of 80 jet rejection
    decreases by 50
  • Muon identification and measurement
  • If enough shielding is provided expect
    reconstruction efficiency and momentum resolution
    not to deteriorate much
  • Forward jet-tagging and central veto
  • Essential handle to increase S/N for WW and ZZ
    fusion processes
  • Performance can be significantly degraded
    though algorithms could be optimised
  • Trigger
  • High thresholds for inclusive triggers use of
    exclusive triggers selecting specific final

Tracking Detectors
  • Clearly, the tracker is crucial for much of the
    LHC physics e.g. e, ?, jets (pileup, E flow), b
  • The existing trackers will not be capable of
    utilizing the increased luminosity as they will
    be near the end of their useful life.
  • It is necessary to completely rebuild the LHC
    tracking detectors.

Tracker - Occupancy
  • The occupancy, O, for a detector of area dA and
    sensitive time time dt at (r,z) is
  • e.g. Si strip 10 cm x 100 ?m in a 12.5 nsec
    crossing at r 20 cm is 1.5
  • For higher luminosity, decrease dA, or decrease
    dt (limit is x-ing time) or increase r smaller,
    faster or further away.

Tracker Occupancy
  • Preserve the performance using
  • Push Si strips out to 60 cm. development
  • Push pixels out to 20 cm. development
  • For r lt 20 cm. Need new technologies basic
  • Shrink dA 5x at fixed r to preserve b tagging? If
    12.5 nsec bunchx, need 5x pixel size reduction.
  • Possibilities
  • 3-d detectors electrodes in bulk columns
  • Diamond (RD42) - radhard
  • Cryogenic (RD39) fast, radhard
  • Monolithic reduced source capacity.

Monolithic Pixel - DEPFET
Combine the detector and the readout for pixels?
Tracker Ionizing Dose
  • The ionizing dose due to charged particles is
  • The dose depends only on luminosity, r, and
    exposure time ?.
  • For example, at r 20 cm, the dose is 3 Mrad/yr
    ignoring loopers, interactions, .

Tracker ID vs. Radius
Define 3 regions. With 10x increase in L, need a
3x change in radius to preserve an existing
Tracking RD -I
  • Region 1 r lt 20cm
  • Occupancy -gt Need pixels of a size factor 5
    smaller than used today
  • (125x125 ?m2 -gt 50 x 50 ?m2) -gt benefit
  • RD Pixels Sensor Technologies
  • new sensor materials defect engineered Si, CVD
    diamond, SiC, passivated amorphous Si etc.
  • 3-D detectors and new biasing schemes
  • Cryogenic Si tracker development
  • monolithic pixel detectors
  • Region 2 20ltrlt60 cm
  • Need cell sizes 10 times larger than current
    pixels but at 10 times lower cost/channel than
    current Si microstrips -gt benefit p-resolution
    and pattern
  • Si Macro-pixels of an area lt 1mm2 pads or
    shorter ?strips ?
  • Could be upgrades of innermost Si microstrip
    layers of current detectors
  • RD to demonstrate low-cost macro-pixels
    concept, thin Si detectors.

Tracking RD - II
Region 3 r gt 60 cm Si-strips decrease size of
strips i.e. increase no. of channels by gt 50 Use
standard radiation resistant ?strip
technology RD Feasibility of processing
detectors on 8 or 12 Si wafers. Monitor
commercial production progress. Engineering RD
new materials, light weight, stable structures,
cooling, alignment, implications for cryogenic
operation, installation and maintenance
aspects Activation 250 mSv/h implications for
access and maintenance Cost Reduce cost/channel
by a factor of 10 Timescale Need 8-10 years
from launch of RD 4 years to build, after
4 years of RD and prototyping ?
Electronics Moores Law
  • Micro-electronics line-widths decrease by a
    factor 2 every 5 years. DSM (0.25 ?m) is
    radiation hard.Today 0.13 ?m is commercially
    available. In the lab 0.04 ?m, e.g. extreme UV
    lithography, is in existence. Expect trend will
    continue for a decade.
  • RD
  • Characterize emerging technologies
  •  more radiation tolerance required dose and
    Single Event Effects
  •  advanced high bandwidth data link technologies
  • system issues addressed from the start

ECAL Shower Dose
  • The dose in ECAL is due to photon showers and
  • In the barrel, SD is . In the
    endcap, SD
  • At r 1.2 m, for Pb with Ec 7.4 MeV, the dose
    at y0 is 3.3 Mrad/yr, at y1.5 it is 7.8

HCAL and ECAL Dose
The dose ratio is
. Barrel doses are not a problem. For
the endcaps a technology change may be needed for
2 lt y lt 3 for the CMS HCAL. Switch to quartz
fiber as in HF?
  • For both ATLAS and CMS the barrel will probably
    tolerate the increased dose. There are issues of
    2.2x increased pileup noise and poorer
    isolation for electrons. Shorter shaping times to
    resolve x-ing?
  • ATLAS LA has space charge and current draw
    issues. CMS has APD leakage current noise issues
    in the barrel. The CMS endcap needs development.

Calorimeters CMS ECAL
Crystals Barrel OK Endcap 3krad/hr at
y2.6 Further studies at high dose rates, long
term irradiation Photosensors Barrel APDs
higher leakage current a higher noise 100
MeV/ch Endcaps VPTs RD on new devices may
be needed Electronics Barrel OK Endcap RD
More rad-hard electronics at y3? Activation
in endcaps reach several mSv/h access will be
Calorimeters ATLAS LAr
Space Charge Effects GeV/cm2/s Comfortable margin
in Barrel. Inner parts of em endcap and FCAL
may be affected
HV Voltage Drop Comfortable margin in Barrel.
Small wheel of em endcap sees a large
current precision meas. not possible
Electronics Probably OK? RD Use of another
cryogenic liquid, with less charge deposited per
GeV, or a cold dense gas to address issues of
space-charge and HV voltage drop
Critical density
  • Both ATLAS and CMS will function in the barrel
  • In the 3ltylt5 region, a reduction to y lt 4.2
    keeps the dose constant. The loss of efficiency
    is not terrible (peak tagrate at y3). Or
    replace quartz fibers with high pressure gas?
    Better tower granularity might be needed due to
    pileup and fake jets.
  • At y 3 the CMS scintillator needs development
    improved scintillator or go to quartz fibers (
    volume degraded is quite small).

HCAL - Coverage
Reduced forward coverage to compensate for 10x L
is not too damaging to tag jet efficiency
Scintillator - Dose/Damage
This technology will not survive gracefully at
y 3. Use the technology that works at LHC up
to Y 5, quartz fibers.
Muons and Shielding
There is factor 5 in headroom at design L. With
added shielding, dose rates can be kept constant
if angular coverage goes from ylt2.4 to ylt2.
Muon System
  • Current ATLAS/CMS muon systems designed with
    safety factor of 3-5 w.r.t. background
    estimations (establish real safety margin once
    LHC operates)
  • Strong geometric dependence of particle and
    radiation induced rates ,
  • Possible strategy
  • extra shielding at high ? reduces background
  • restrict high ? limit of muon acceptance
  • Radio-activation at high ? of shielding, supports
    and nearby detectors
  • - may limit maintenance access
  • Balance super robust detectors vs shielding
    and reduced high- ? acceptance
  • RD Study limit of current detectors - use of
    CSCs in barrel,
  • At high- ? - higher rates use straw chambers?

Trigger and DAQ
  • Assuming LHC initial program is successful, raise
    the trigger thresholds.
  • Rebuild trigger system to run at 80 MHz. Utilize
    those detectors which are fast enough to give a
    BCID within 12.5 nsec (e.g. Calorimetry,
  • Examine algorithms to alleviate degraded e
    isolation, for example.
  • Design for the increased event size (pileup) with
    reduced L1 rate and/or data compression.
  • For DAQ track the evolution of communication
    technologies, e.g. 10 Gb/sec Ethernet.

300 GeV Pion H2 test Beam
HTR - Bunch crossing number (LHC)
The shape of the pulse in time is as expected
due largely to scint flours. Bunch crossing ID
can be extended to 12.5 nsec ( 80 MHz) as
established in test beam.
Level-1 Trigger
  • Trigger Menus
  • - Triggers for very high pT discovery physics no
    rate problems higher pT thresholds
  • - Triggers to complete LHC physic program final
    states are known use exclusive menus
  • - Control/calibration triggers with low
    thresholds (e.g. W, Z and top events) prescale
  • Impact of Reduced Bunch Crossing Period
  • Advantageous to rebuild L1 trigger to work with
    data sampled at 80 MHz
  • Could keep some L1 trigger electronics clocked
    at 25 ns
  • Require modifications to L1 trigger and detector
    FE electronics
  • RD Issues
  • Data movement is probably the biggest issue for
    processing at 80 MHz sampling
  • Processing at higher frequencies and with higher
    input/output data rates to the processing
    elements, although technological advances (e. g.
    FPGA ) will help
  • Synchronization (TTC, etc) becomes an issue for
    short BC period

  • Continuous and extraordinary evolution of
    computing and communication technologies
    monitor the evolution of
  • Readout Network
  • Follow LHC machine luminosity exploit parallel
    evolution of technologies
  • main building block of DAQ is the switch
    interconnecting data sources (event digitizers)
    and processing nodes (event filters)
  • rapid progress in interconnection technologies
    started recently LHC needs cannot yet be
    satisfied using a completely off-the-shelf system
  • Technology Tracking
  • Complexity Handling
  • Online computing systems will have 10000 CPUs,
    issues of hardware and software management,
    reliability,remote access, security, databases
  • Technology Tracking (e.g. those found in ISPs)
  • RD How to handle bandwidth (rate ? size)
    Bandwidth is an issue both for readout and for
    event building

  • The LHC Physics reach will be substantially
    increased by higher luminosity.
  • To realize that improvement, the LHC detectors
    must preserve performance.
  • The trackers must be rebuilt with new
    technology at r lt 20 cm.
  • The calorimeters, muon systems, triggers and DAQ
    will need development.
  • The upgrades are likely to take (6-10) years.
    Accelerator is ready (2012, 2014). The time to
    start is now, and the people to do the job are
    those who did it for the present detectors.