Manfred Jeitler, HEPHY Vienna Level-1Trigger in 2012 Lisbon, 6 Sep 2012 1

Level-1 Trigger in

2012

Manfred Jeitler

HEPHY Vienna

-90 kHz rate

- 3% deadtime CM

S r

un

201

624

L

HC

Fill

299

8

Manfred Jeitler, HEPHY Vienna Level-1Trigger in 2012 Lisbon, 6 Sep 2012 2

challenges and performance in 2012

LHC very successfully increased luminosity up to almost 8e33

– PeakLumi = 7573.567×1030cm-2sec-1

– PeakPileup = 34.117

– in run 201624 (fill 2998)

cope with this without losing good data!

Manfred Jeitler, HEPHY Vienna Level-1Trigger in 2012 Lisbon, 6 Sep 2012 3

plot by Darin Acosta

challenges and performance in 2012

Manfred Jeitler, HEPHY Vienna Level-1Trigger in 2012 Lisbon, 6 Sep 2012 4

challenges and performance in 2012

more and more trigger algos must be disabled !

(mapopripped)

plot by Darin Acosta

Manfred Jeitler, HEPHY Vienna Level-1Trigger in 2012 Lisbon, 6 Sep 2012 5

muon rate strongly suppressed... ...while keeping the efficiency

mainly by better pt assignment in CSC Track Finder also by more sophisticated merging scheme in GMT

– Global Muon Trigger

rate down by 50%– over full range

– 30% for |η|<2.1

shown in plot

Manfred Jeitler, HEPHY Vienna Level-1Trigger in 2012 Lisbon, 6 Sep 2012 6

calorimeter jet seed threshold

jet an especially HT rates are strongly pileup dependent– HT is ET summed over identified jets above (low) energy threshold

» 10 GeV

– overall illumination of calorimeter creates fake jets

cure: introduce threshold for jet “seed” – currently 5 GeV

must be done in GCT– Global Calorimeter Trigger, upstream of GT (Global Trigger)

– outside of “Level-1 trigger menu”

very effective in reducing rates

Manfred Jeitler, HEPHY Vienna Level-1Trigger in 2012 Lisbon, 6 Sep 2012 7

calorimeter jet seed threshold

Manfred Jeitler, HEPHY Vienna Level-1Trigger in 2012 Lisbon, 6 Sep 2012 8

L1 trigger close to its present limit ...... but not at the end of its tether!

with LHC’s impressive progress we have had to also improve the trigger– by just raising thresholds we would be losing physics already

substantial improvements achieved this year

some more still be possible

but to profit from the LHC upgrade CMS also must upgrade the L1 trigger

Manfred Jeitler, HEPHY Vienna Level-1Trigger in 2012 Lisbon, 6 Sep 2012 9

L1 upgrade stage zero:optical links between GCT and GT

fast galvanic serial links between GCT and GT had been a worry– no spares available, no data check possible

new electronic modules with optical links installed before 2012 run

– “Optical PSB” (or “oGTI”)

– learning experience for mostly optical connections in upgrade project

CRC check recently implemented must be careful when touching a running system

– due to misconfiguration calo monitoring data were not correctly read for some time

– now fixed, everything working fine– don’t forget certain “features” such as GCT input

masking!

Manfred Jeitler, HEPHY Vienna Level-1Trigger in 2012 Lisbon, 6 Sep 2012 10

Sorry for keeping you

waiting ...

... but we know (now) that you enjoy your L1 trigger just as much if it’s served 12 BX later!

... and it will taste better if cooked a bit longer!

Manfred Jeitler, HEPHY Vienna Level-1Trigger in 2012 Lisbon, 6 Sep 2012 11

Why just-in-time delivery of L1A?

the upgraded trigger will be better than the present system but not faster :

– carry out more complex operations

– collect and use more information for decision making

– use of serial optical links allows using more information (higher bandwidth) and is less error prone (fewer cables that can break) but requires time for SERialization / DESerialization (SerDes)

Manfred Jeitler, HEPHY Vienna Level-1Trigger in 2012 Lisbon, 6 Sep 2012 12

latency + 12 BX test

finding the maximum admissible latency is not trivial because:

Tracker and Preshower might become gradually inefficient at too high latency

can only be checked realistically with data +12 BX on top of present (production) latency is

theoretical maximum– at higher latency inefficiency must occur at some level

the test in June showed that +12 BX is safe!– took a full fill with this latency, data are OK

– rolled back for production afterwards

– we will certainly use this budget for the L1 Trigger upgrade

Manfred Jeitler, HEPHY Vienna Level-1Trigger in 2012 Lisbon, 6 Sep 2012 13

L1 and BPTX

present CMS configuration relies on BPTX beam monitor being fully available all the time– have to tell collision bunches from gaps between:

– for suppressing HF prefiring (see below)

– for calculating the trigger dead time

– for special checks (e.g., beamgas events in unpaired bunches)

this dependence is dangerous– as shown by a few (rare) hickups

other option: just use filling scheme published by LHC– also this is not always failsafe

– ATLAS relied on it and lost some data

Manfred Jeitler, HEPHY Vienna Level-1Trigger in 2012 Lisbon, 6 Sep 2012 14

BPTX : coping with the dependence

ideal: take LHC record and cross-check with BPTX before stable beams– cannot change after ramp

– implementation in progress

in the meantime: have created special configuration key for running without BPTX– not ideal for data but reduced dependence

early warning system in case of BPTX problems– DQM plots developed to warn about problems already during

LHC ramp

what about long-term maintenance of BRM / BPTX ?– small group

– importance tends to be understimated by funding agencies

Manfred Jeitler, HEPHY Vienna Level-1Trigger in 2012 Lisbon, 6 Sep 2012 15

HF Prefiring prefiring of HF from particles hitting the photomultipliers

directly– instead of creating scintillation light in the detector, as a well-behaved

particle should

suppress now by vetoing bunch crossings before a collision crossing– this is why we need BPTX most badly!– “PreBPTX veto”– impossible in 25-ns running– for upcoming 25-ns test: will probably not use

jet triggers

HF will replace all photomultipliers during LS1– hope that this will fix the problem– if not: remove HF from single-object triggers

Manfred Jeitler, HEPHY Vienna Level-1Trigger in 2012 Lisbon, 6 Sep 2012 16

forward physics: collaboration with TOTEM CMS and TOTEM are two separate experiments with

separate DAQ– might change over LS1

but their triggers cooperate– CMS receives several bits from TOTEM over LVDS signals

– some “Technical Trigger” bits, some used in Algorithms

– TOTEM receives from CMS the L1A and some BGOs» via an unused “APVE output”

– including BC0 (“bunch crossing zero”) and OC0 (“orbit counter reset”)

can merge CMS and TOTEM data off line

several successful low-lumi runs taken jointly CMS will use TOTEM’s “T2” for minimum-bias trigger in

upcoming p-Pb test run

Manfred Jeitler, HEPHY Vienna Level-1Trigger in 2012 Lisbon, 6 Sep 2012 17

where is TOTEM?

Roman Pots 9.5 < η < 13140 m, 220 m

Manfred Jeitler, HEPHY Vienna Level-1Trigger in 2012 Lisbon, 6 Sep 2012 18

CMS Talking To TOTEM

Manfred Jeitler, HEPHY Vienna Level-1Trigger in 2012 Lisbon, 6 Sep 2012 19

BCM1F for beam-gas veto?

last year’s beam gas problems prompted studies to reduce effect at Level-1 by using the “BCM1F” detector– fight beamgas-induced high trigger rate by veto signal

– such events may be worse than normal events because of high Pixel occupancy

– Previously Known as PKAMs

– other idea: use HF asymmetry

beam gas much less of a problem in 2012 hard to study the veto performance

– but also less important!

no conclusion yet if this approach will (have to) be used

Manfred Jeitler, HEPHY Vienna Level-1Trigger in 2012 Lisbon, 6 Sep 2012 20

give me more ...

backup slides

Manfred Jeitler, HEPHY Vienna Level-1Trigger in 2012 Lisbon, 6 Sep 2012 21

BC0 L1A @BX=a

L1A @BX=a+m+n

L1A @BX=a+m

physics triggers

Manfred Jeitler, HEPHY Vienna Level-1Trigger in 2012 Lisbon, 6 Sep 2012 22

BC0

calib @BX=3490

calib @BX=3490+m+n

calib @BX=3490+m

TEST ENABLE @ same BX as before

calibration trigger