ATLAS Forward Protons and TriggerAndrew Brandt (UT-Arlington)

DOE ReviewNov. 14, 2008Arlington, TX

•Who am I? B.S. College of William&Mary 1985 PH.D. UCLA/CERN (UA8 Experiment-discovered hard diffraction) 1992 1992-1999 Post-doc and Wilson Fellow at Fermilab -Discovered hard color singlet exchange JGJ -1997 PECASE Award for contributions to diffraction -Proposed and built (with collaborators from Brazil) DØ Forward Proton Detector -QCD and Run I Physics Convenor -Trigger Meister, QCDTrigger Board Rep., Designed Run II Trigger List 1999-2004 present UTA Assistant Prof 2004-present Assoc. Prof -OJI, MRI, ARP awards for DØ FPD -2005 started fast timing work (ARP, DOE ADR) -2008 sabbatical on ATLAS

•ATLAS Forward Protons•ATLAS Trigger•Miscellaneous related stuff

Forward Protons at LHC (FP420, AFP)Central Exclusive Higgs production pp p H p : 3-10 fb

beam

p’

p’roman pots

dipole

dipole

22 )''( ppppM H

E.g. V. Khoze et alM. Boonekamp et al.B. Cox et al. V. Petrov et al…Levin et al…

M = O(2.0) GeV

Hgap gap

b

b -jet

-jet

p p

``The FP420 R&D Project: Higgs and New Physics with ForwardProtons at the LHC,'' FP420 R&D, arXiv:0806.0302 [hep-ex].

``Letter of Intent for ATLAS FP: A project to installforward proton detectors at 220 m and 420 m upstream and downstream of the ATLAS detector,'' A. Brandt, B. Cox, C. Royon et al., AFP Collaboration, http://www.cern.ch/jenni/AFP.loi\_atlas.pdf.

I had a major editorial rolein both documents and amon the Management Boardof both groups

Physics of AFP

• At lowish luminosity (30-60 fb-1) we can : Establish the quantum numbers of SM Higgs Be the discovery channel in certain regions of the MSSM Make high precision measurements of WW / ZZ couplings Perform interesting QCD measurements (0.002 < xIP < 0.015 )

•In addition, at higher luminosity (> 100 fb-1) we can : Discover exotic bound states such as gluinoballs Make direct observation of CP violation in some SUSY Higgs scenarios Disentangle wide range of SUSY scenarios, including ~degenerate Higgs

•FP420 turns the LHC into a energy tunable glue-glue (and ) collider

FP420 Components

• Modified Cryostat to create space for detectors and allow detector movement close to the beam

• 3D silicon detector for position measurement (also being developed as a solution for ATLAS upgrade silicon detector due to rad hardness)

• Fast TOF counter for pileup rejection

Pileup Background• Example: 3 interactions, one with hard scatter, and two with diffractive protons

• This is a huge concern due to high rates of single diffraction (1% of diffractive protons give a hit within the detectors)

• At UTA we (Brandt, Duarte, Pal, Spivey, Howley) have been addressing this issue in two ways:

1) By studying exclusive Higgs signal and pileup backgrounds, developing and testing new

pileup rejection variables

2) By developing a timing detector to reject events where the protons do not come from the central vertex

10 picoseconds original design goal(light travels 3mm in 10 psec!)gives large factor of background rejection;phased plan, start with 20 ps (<2 year timescale),need better than 10 ps for full machine luminosity (<4 years)

Use time difference between protons to measure z-vertex and compare with tracking z-vertexmeasured with silicon detector

Pileup Background Rejection

Test Beam Studies for FP420 Fast Timing

WHO?Developers: UTA (Brandt), Louvain, Alberta, FNAL

WHY?

How?

How Fast?

TB shifters: UTA, UC-London, Louvain, Prague

Fast Timing Is Hard!

• 3 mm =10 ps• Detector• Phototube• Electronics• Reference timing• Rad Hardness of detector, phototube and

electronics, where to put electronics in tunnel• Lifetime and recovery time of tube, grounding• Background in detector and MCP• Multiple proton timing

ISSUES Time resolution for the full detector system:1. Intrinsec detector time resolution2. Jitter in PMT's3. Electronics (AMP/CFD/TDC)

FP420 Baseline Plan1 GASTOF 2 QUARTICs

Lots of 3D siliconTwo types of Cerenkov detector are employed:

GASTOF – a gas Cerenkov detector that makes a single measurement

QUARTIC – two QUARTIC detectors each with 4 rows of 8 fused silica bar allowing up to a 4-fold improvement over the single bar resolution

Both detectors use Micro Channel Plate PMTs (MCP-PMTs)

The Detectors : 1) GASTOF(Louvain)

Not so much light since use gas,but full Cerenkov cone is captured.Simulations show yield of about 10 pe accepted withinfew ps! 1 measurement of ~10 ps

4x8 array of 6 mm2 fused silica bars

The Detectors : 2) QUARTIC

UTA, Alberta, FNAL

Only need 40 ps measurement if you can do it 16 times (2 detectors with 8 bars each)!

proton

phot

ons

Updated station layout.

3D silicon + GASTOF or QUARTIC

Mobile BPM welded on station and calibrated with respect to pockets

Test Beam Layout

Latest QUARTIC Prototype

Testing long bars 90 mm (HE to HH) and mini bars 15 mm (HA to HD) Long bars more light from total internal reflection vs. losses from reflection in air light guide, but more time dispersion due to n()

HE

HH

HC

QUARTIC Ray Tracing

20 ps

~ 5 pe’s accepted in 40 ps

40 ps

40 ps

~ 10 pe’s accepted in 40 ps

15mm Quartz/75 mm air

90mm Quartz

Electronics

MCP-PMT Preamplifier SMA

LCFD Fast Scope

SMA

SMA Lemo

Fast Scope

For GASTOFreplace CFD/TDCwith single photon counter

QUARTIC:Photonis Planacon10 m pore 8x8Gastof:Hamamatsu 6 m pore single channel or equivalent Photek

Mini-circuits ZX606 GHZ or equivalent

Louvain Custom CFD (LCFD)

HPTDC board(Alberta) interfaces to ATLAS Rod

(a) Experiment channel

(b) or (c) TB channel

FP420 Timing Setup

G1G2

Q1

Amplifiers

Data Acquisition

• Lecroy 8620A 6 GHz 20 Gs (UTA) • Lecroy 7300A 3 GHz 20/10 Gs (Louvain)• Remotely operated from control room using TightVNC• Transfer data periodically with external USB drive

UTA funding from DOE ADR grant and Texas ARP grant

Good Event

5 ns/major division

Online Screen Capture

one histo is 10 psper bin others are 20 ps

histogramdelta timebetweenchannels

FWHM<100so /2.36 ->dt~40 ps

Offline Analysis

• Too cumbersome, not getting results in timely manner• I implement streamlined approach + round the clock analysis

shifts (one data taking shifter, one analysis shifter: Nicolas, Vlasta, Shane)

-start with basics -plot pulses -pulse heights -low threshold cut -raw times -time differences -add tracking later

overflow -> switch from 100 to 200 mv scale

acceptance

Determining Pulse Time

Burle (HF)

Hamamatsu(G1)

LCFD (HFc)

Linear fit, use 50% time

Dt

QUARTIC Long Bars after LCFD

56.6/1.4=40 ps/bar including CFD!

Time difference between two 9 cm quartz bars after constant fraction discriminationis 56 ps, implies a single bar resolution of 40 ps

LCFD Resolution

Split signal, take difference of raw time and CFD time-> LCFD resolution <27 psThis implies detector+tube ~30 ps

6 mm

6mm

Eve

nts

Strip #

Eff

icie

ncy

(a) (b)

(c)

Tracking /Scope Synchronization

All tracks HEc On

Use tracking to determine that QUARTIC bar efficiency is high and uniform

GASTOF On

GASTOF Displaced 19 mm

All tracks

dip ~1 mmwide

Multiple scatteringeffects in 400 um wide, 30 cm long stainless steel edge of GASTOF (cause veto)!1mm depletion impliestracking projection issues, detector tilted slightly, or both

edge

Laser Tests

laser diode lenses filter splitter

mirror PMT

Debugging laser setupcurrently 25 ps resolution for achannels of 4 channel 25 mtube, will study as fct. of filterand HV

Howley, Hall, Lim

ATLAS Forward Proton Summary and Outlook

• June TB two weeks of running, tremendous effort• 100+Gb of scope data, sizable fraction synchronized

with tracking from Bonn telescope• Demonstrated good data, now finalizing results, plan to write a paper this year • LOI submitted to ATLAS in September• Will need more laser tests, simulation and test beam

before design is finalized• Plan to continue tests and help secure ATLAS approval

of LOI, build U.S. ATLAS collaboration for Phase 1+2 funding

Sabbatical/Trigger

• Major emphasis of Sabbatical was to start new UTA effort on ATLAS trigger (with Sarkisyan+Pal)

• Organized Trigger Robustness Workshop

• CSC chapter editor

• Forward jet commissioning

• Minbias Trigger Validation + Low PT tracking

• Dijet trigger rates

• Diffractive triggers

• Chair Trigger Rates group, added to Trigger Coordination Group (continuing responsibility)

• Many talks in menu+jet meeting, SM talk, 2 plenary talks, joined Tdaq

Trigger Robustness Workshop

was held March 4, 2008 at CERN

Goals: 1) Evaluate ability of trigger system to cope with readout, detector, and beam related problems2) Generate list of problems and a strategy to address them

organized by: Andrew Brandt (UT-Arlington) Ricardo Goncalo (Royal Holloway)

Successful one day workshop with 25 short talks and lots of discussion

Agenda: http://indico.cern.ch/conferenceOtherViews.py?view=standard&confId=29007

Robustness twiki to document progress and follow-up:https://twiki.cern.ch/twiki/bin/view/Atlas/TriggerRobustness

The UnknownAs we know, There are known knowns. There are things we know we know. We also know There are known unknowns. That is to say We know there are some things We do not know. But there are also unknown unknowns, The ones we don't know We don't know.

—Feb. 12, 2002, Department of Defense news briefing

Gordon Watts got us off to a rousing start with a quote

from anInfamous American Poet on

large experiment Trigger/DAQKnown

problem

s

Ununderst

ood problems Don’t

even know you

have them

problem

s

!

Automated Systems (or shifters)Experts and Detector/Trigger GroupsG. Watts (UW/CPPM)

Beam-related Background• Result: Several slices (muon, MET, jet) showed insensitivity to beam

backgrounds using halo (from scattering off tertiary collimator) and beam gas events generated by Alden Stradling (Wisc./UTA).

-Halo events provide low pT muons but these did not tend to give triggers. Absolute beam gas rates are expected to be very low.

-The level of impact on the trigger was consistent with noise in the detector, such that if jet thresholds are at least 10 GeV and MET thresholds at least 25 GeV, then very little impact on trigger is expected, even if backgrounds were to be much worse than anticipated.

-Provided important information to ATLAS beam background WG (of which I was a member)• Follow-up: Encouraging results indicate that beam backgrounds are not likely

to be a serious issue for trigger, nevertheless HLT algorithms to recognize unphysical patterns of energy deposition are being developed, should the rates turn out to be unexpectedly large. Generation of larger and more complete data samples should be pursued.

33

Dijet Samples: Rates&More

•Current trigger rates for experiment at 1031 calculated using a 7 Million event minimum bias sample, gives large rate uncertainty as luminosity goes up, Ex. 1 event = 10 Hz at 1033 (1 nb = 1 Hz at 1033)•Started investigating strategy for better rate measurements (see March 19 menu talk, March 26 jet talk, April 9 menu talk, April 16 jet talk)•Some of the results may be relevant for Standard Model Jet Physics

Andrew Brandt (UT-Arlington)

SM MeetingMay 6, 2008CERN

Big thanks to Edward Sarkisyan-Grinbaumfor plots, endless MC generation, Arnab Pal, Marc-Andre, Bilge for rate help

8-17

0.4nb-> don’t care about J6-J8!

J0(J2) 2(3) M events other samples 400-600k (200k for J8)

34

Standard Jx Samples Harder than Min Bias

Reco

Truth

With some pain we found this was due to MC version; MB was PYTHIA 6.4 while Jx was PYTHIA 6.3

Note: sum of Jx’s (black-dashedcurve) is greater than blue min bias,for standard dijet samples

35

Agreement Between Our J0-J3 and MB

We used PYTHIA 6.412with ATLAS default tune,scaled by number of events and cross section ratio(we used 70 mb for min bias)

Note messy features of upper cuts samples: turn-on and turn-off,mixing of bins, statistical fluctuations

36

PYTHIA 6.3 vs. 6.4

J0 PYTHIA 6.323 (default sample)

J0 PYTHIA 6.403

J1 PYTHIA 6.3

J1 PYTHIA 6.4

J2

J3Differences large at low pT small at high pT

37

PYTIA 6.3 vs. 6.4 Difference

• “Weird” events at high pT of PYTHIA 6.3 samples apparently due to new shower model which showers to beam energy cutoff scale instead of hard parton scale. This effect occurs in all bins, but causes most significant problems in low pT bins since these bins have a big weighting factor and the effects are relatively much more significant for low parton pT

• Although it is not guaranteed that PYTHIA 6.4 is more correct than 6.3, it is now the default to have less showering and it seems to make better physics sense

(see rates)

38

Trigger Rate Implication• Abnormally high trigger rates clearly due to

PYTHIA 6.3 vs 6.4 difference (*my office!)

Selected Trigs

MB Jx J0 (Hz) J1 J2 J3 J4

4j35 32 203 123 35 16 23 6

3j50 63 173 86 22 13 40 11

j200 15 20 7 3 2 1 7j33 .0043 .0050j84 1.1 1.39 .5 .2 .2 .5 j120 1.36 1.66 .5 .3 .1 .5 .3

Implies multi-jet rates way over-estimated, and single jet rates over-est. by ~30%

JNu Samples

Convinced ATLAS management to try JNu (no uppercut filtered samples)for trigger rate and possibly physics studies (real life has no uppercut!)

Edward Sarkisyan-Grinbaum Edward Sarkisyan-Grinbaum (UTA)• ATLAS Performance and Physics Workshop (Nov. 5-7, 2008)• Tracking Session & Standard Model Meeting

• http://indico.cern.ch/conferenceDisplay.py?confId=41483

Low-pT Tracking Performance

• A key ingredient of basic (very) A key ingredient of basic (very) early measurementsearly measurements

• Physics interests: early QCD, minbias, diffraction, gaps, jets…Physics interests: early QCD, minbias, diffraction, gaps, jets…

• Critical for understanding underlying events, pile-up, precise Critical for understanding underlying events, pile-up, precise

measurements backgroundmeasurements background

• Practical interest: detector, SW comissioning, tuning modelsPractical interest: detector, SW comissioning, tuning models

Why low-pT TrackingWhy low-pT TrackingReconstruction is difficult: high curvature of tracks, increased multiple scattering, reduced # of hits

Low-Pt tracking completes the full track-finding strategy (global-chi2, Kalman-filter, dynamic noise adjustment, Gaussian-sum filters, deterministic annealing filter, pattern recogn., back track-finding)

Subset of Edward’s Current ActivitySubset of Edward’s Current Activity

• Efficiency and fake rates studies based on truth matching

• Comparison of different physics processes such as Minbias - SD - DD

• Studying hits in different tracking sub-detectors• Rerunning GEANT4 simulations with lower thresholds• Studies to look for secondaries that might be mistaken

as primaries (vertex, impact parameter studies) • Minbias Validation• Min bias and gap physics

43

Diffraction in ATLAS•Diffraction is a top level physics group in CMS, but until very recently, there was almost no diffraction in ATLAS•Discussion of soft diffraction, but only as background to min bias (that really hurts!)•There was a Luminosity and Forward Detector WG with the idea of possibly doing diffractive physics with ATLAS pots•Andrew Pilkington (Manchester) and I started grass roots effort early this year now we have risen to sub-sub group status! (as part of SM sub-group with QCD+MinBias)•Early focus is on two topics: 1) Central Exclusive Diffraction 2) Gaps between jets

jet

jet

(ET > 30 GeV, s = 1800 GeV)

DØ EVENT

44

ATLAS Gap Trigger StrategyJet Trigger Prescale (L1) Rate (Hz)

J10 42000 3.9

J18 6000 1.02

J35 500 1.37

J42 100 3.73

Standard jet thresholds too highly prescaledfor CEP studies.

Short term option:Use MBTS information to define a lack of activity in the forward region.

Long term goal:Use MBTS, BCM, LUCID and ZDC to definea variety of gap definitions.

Possible gap triggers in 10TeV run:• Require one jet passing J18 (J10 probably too noisy,

J35 too high) + veto on MBTS_1_1 (veto of hits on both sides means no hits on one side or

no hits on either side). • Investigating other MBTS terms such as inner ring

veto on one side + outer ring coincidence on other • Space points at L2 could be used to suppress L1Calo

noise

45

Gap Trigger Efficiency

• Gap trigger is ~65% for EXHUME CED signal sample (pT>35 GeV)

– Gives 10k rejection of non-diffractive; would bring prescale close to 1

MBTS vetoadded

46

Gap Summary

• Central exclusive production can be measured with

10-100pb-1 of data.– Helps to understand underlying event, parton

distributions, Sudakov suppression– Constrains theoretical models on diffractive Higgs

• Forward jet measurements with early data can shed light on the nature of hard color singlet exchange.

– Only needs ~10 pb-1 of data.

– Helps understand forward jets for VBF studies

• Triggers added to default trigger list

ATLAS Activities Summary/Outlook

• With excellent support from DOE and UTA, I had a very successful sabbatical opening up new trigger areas, some of which I will continue in coming year (especially trigger rates)

• Edward also got fully integrated (joined UTA in Feb.)• Plan to continue with AFP studies and approval• Will pursue project funds for trigger work• Need adequate travel support to allow four trips to CERN

+ one month in summer to maintain effectiveness in ATLAS