atlas-cms slhc workshop, 20/3/07 costas foudas, imperial college london 1 results from studies for a...

ATLAS-CMS SLHC Workshop , 20/3/07 Costas Foudas, Imperial College London

1

Results from Studies for a Tracking Results from Studies for a Tracking Trigger for CMS at SLHCTrigger for CMS at SLHC

Overview of this talk:

• Trigger Goals at SLHC• Expected rates and occupancies at SLHC• What do we know so far from LHC studies• Proposals for Tracking Trigger


2

Minimum Bias Events, a ReminderMinimum Bias Events, a Reminder

• SLHC (1035 ; 80 MHz): 110 (less likely now)• SLHC (1035 ; 40 MHz): 220• SLHC (1035 ; 20 MHz): 440

22

70 mb deep inelastic component


3

Triggering at the SLHC with CMS Triggering at the SLHC with CMS

• Luminosity will go up by ~ factor of 10• The clock will be 20 or 40 Mhz• The FLT latency will be 6.4 sec (true for 40 MHz)• Maintain L1-Output at 100 KHz• Hence, given that the backgrounds will go up by a

factor of 10 (40 MHz) or even 20 (20 MHz) one needs to cut the rate at FLT.

• The obvious thing to do is to use tracking information in producing the L1 decision.


4

SLHC TriggersSLHC Triggers• Assuming that one decides to include the

tracking information in the L1-Accept decision, a look at the HLT algorithms prepared for LHC shows what needs to be done:

• Electron Triggers

• Tau Triggers

• Muon Triggers

• Jets triggers ?


5

SLHC RatesSLHC Rates

• Rates calculated using CMS software (ORCA) at 80 MHz double them for 40 MHz.

• No charge sharing has been included. Hence, another factor of at least two to make them realistic. 10 Gb/s/cm2 100 Tb/s

C.Foudas, A. Rose, J. Jones, G. Hall, LECC2005, Heidelberg


6

Check against older CMS resultsCheck against older CMS results

• The simulation results are consistent with early CMS results from the Tracker TDR.

• Later will give the result which included all other effects such as charge sharing

A. Rose MSci thesis Imperial 2004


7

Electron TriggersElectron Triggers

• Gain a factor of 10 by requiring a hit in the inner tracker • Another factor of 3 from using the outer tracker.• Inner Tracker is absolutely essential for a tracking trigger.

G. Daskalakis CMS Note 2002-39


8

Tau TriggersTau Triggers

• Tau Triggers also require isolated high pt stubs in the inner tracker to detect hadronic decays of taus (65%).

• The QCD jet efficiency can be reduced by a factor of 10 while tau jet efficiency rises to 75 %.

Efficiency for QCD events


9

Muon TriggersMuon Triggers

• Large Factors to be gained also for muons.• Outer tracker subs may be important here.


10

Tracking Trigger ChallengesTracking Trigger Challenges• Need to design a system which finds high Pt stubs

and places them in coincidence with L1-Cal and L1-Muon triggers.

• Raw rate from the detector needs to be reduced otherwise power and large number of electronic components (useful for trigger but inactive material

for others) will make the idea prohibitive.

• Some kind of a hit correlation finder, correlator, is needed since to reduce the number of combinatorics before one attempts to find tracks and correlate with calorimeter L1 trigger objects.


11

The Stacked Tracker idea The Stacked Tracker idea • Have a stacked pixel detector where the

two layers have a radius difference of few mm.

• Require coincidences between the pixels of the two layers to select high Pt stubs

Momentum cut.• Removes all the low pt particles.• See: J. Jones et al. , A Pixel Detector for

L1 Triggering at SLHC, LECC 2005

α


12


13

ComponentOutput

bandwidth per unit

Rate Reduction

Number of units per upstream

component

Total number of

units

Aggregateoutput

bandwidth

Sensor (20cm2)10Gb/s cm2

N/A ~0.4 ~1600 ~140Tb/s

Hit Correlator(5 per 20cm2

stack)~1.6Gb/s X50 ~2 ~2000 ~3Tb/s

Opto TX and SERDES

~3.2Gb/s N/A 12 ~1000 ~3Tb/s

12xSFP to SNAP12 Cable

~40Gb/s N/A 5 ~90 ~3Tb/s

Regional Track Generator

~50Gb/s X4 ~3 ~18 ~1Tb/s

Global Track Generator

~4Gb/s X40 ~6 ~6 ~25Gb/s

Global Track Sorter

~10-20Gb/s

X2? N/A 1 ~10-20Gb/s

Bandwidth RequirementsBandwidth Requirements


14

Two Stacked DetectorsTwo Stacked Detectors

• By introducing a second double stacked detector one can measure angles and transverse energy of tracks at reasonable resolution.

• See: J. Jones, A. Rose et al., Stacked Tracking with CMS at SLHC• LECC 2006, Valencia.


15


16

Rapidity and Pt resolutionRapidity and Pt resolution

= 10-3 – 10-4

PT / PT = 10-2


17

Summary and OutlookSummary and Outlook

• Electron Trigger Studies: A. Rose• Detector Designs/ideas: J. Jones• Need urgently to look into muon, tau and other triggers.• Some Algorithm development on FPGA (Virtex-II Pro) by IC

MSci Students already done.• Intend to study more algorithm developments using the V5

Card (see M. Stettler’s talk and M-TCA backplane)• A number of CMS collaborators have signed up for the V5

project (Maryland, Imperial, Wisconsin) with Bristol playing a significant role in Simulations and algorithm development.

• Need urgently collaborators for the most important part of this namely the detector part (Detector design, ASIC-Correlator and Electronics)

atlas-cms slhc workshop, 20/3/07 costas foudas, imperial college london 1 results from studies for a...

Documents