Forward Trigger Upgrade and AuAu Pattern Recognition

V. Cianciolo, D. SilvermyrForward Upgrade Meeting

August 18-19, 2004

2

Motivation• This group is proposing to upgrade the

Muon Arms to increase their trigger rejection power in pp collisions.

• We suffer from significant inefficiencies in central AuAu events.

• Can we solve both problems at once?

3

AuAu Efficiency Loss• J/ efficiency in central AuAu

events is ~20 (30)% for the North (South) Arm

• Reconstruction code still under development, but ~50% of clusters have contributions from >1 track.

• The statistical improvement cannot be much better than x3.

– For most measurements it is hard to justify large expenditures for a “marginal” improvement.

– For low-statistics, low S/N signals (J/ in central AuAu collisions) this improvement can be crucial (e.g., by reducing a 3-year measurement to a 1-year measurement).

• Also a systematic effect.– When the efficiency is low any error

on our calculation of that efficiency (due to incomplete simulation of real-life effects) is magnified in the cross section determination.

North

Arm

J/

Effi

cienc

y

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How Can The Trigger Upgrade Help? Reduce Occupancy

• Assume 1-degree -slices (based on discussions w/ Wei) • We set a goal of 0.5% occupancy and find we need 28 (20) -pads

per -slice for station 1 (station 3).• Plots show occupancy (vs. ) South Arm MuTR Stations 1 and 3 for

200 AuAu “central” events.– Minimum bias events scaled up by x4. – 24 equal- pads per -slice.– Note: for station-1 equal- pads are probably not the optimum choice,

but that’s not important for now.

(degrees) (degrees)

Occ

upan

cy O

ccup

anc

y

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Would 2D info really help with AuAu reconstruction?

• We can’t make a iron-clad case now.– Someone would need to incorporate a hypothetical detector into PISA, run some simulations and

re-tool the reconstruction algorithm. – Hugo, Melynda, etc. could comment on the feasibility of this.

• However, consider all hits on station-3 in MB AuAu events. We determine the number of possible partner hits on station-1 based on two cuts:

– () < 23 - 9/15()– () < 23 - 9/15() && < 1– These two cuts are appropriate for 2.5 GeV muons (pmin of interest to heavy flavor)

• We then count the number of combinations per station-3 hit (left) and per event (right).

• The basic contention motivating these plots is that high-strip occupancy leads to stereoscopic ambiguity, thus eliminating much of the segmentation in the orthogonal direction at the pattern recognition stage.

(degrees) (degrees)

Red – -cut onlyBlack – and -cuts

Red – -cut onlyBlack – and -cuts

# C

ombi

natio

ns p

er S

t3

Hit # C

ombi

natio

ns p

er

Eve

nt

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“Known” Benefits of 2D Info• You really know where the hits are.

– You know how many hits contributed to a cluster.– This must help w/ fitting cluster position.– Deprecate the weight of those clusters?

• Most hits have no potential high-momentum partner – why do any cluster fitting for them?

• You have (many) fewer combinations that need to undergo detailed reconstruction.

• Both seem like great potential for significantly reducing execution time.

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Downstream Chamber Location?• Collision-related hit density highest in “gap-5” due to splash off DX.• Tight correlation should be lost in “gap-5” due to multiple scattering. For the trigger, go in between station-3 and gap-0.

• Having 2D info in back of the MUID may help with heavy flavor measurements in AuAu and may also be important for W physics, but not from a trigger point of view. They would make it significantly more difficult to falsely extend a track by combining it with a hit from behind.

Gap

0

Gap

1 Gap

2 G

ap

3 Gap

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“Gap 5”

MuI

D G

ap H

its (2

00 A

uAu

MB

Eve

nts)

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PC FEE• David points out that there are 90k channels

of PC electronics currently on the shelf (~half in the form of chips, half assembled into Readout Cards (ROCs)).

• Each ROC has 48 channels and 4 trigger bits.– With suggested segmentation a ROC would cover

a 2 degree slice, and each 1 degree slice would have 2 trigger bits (one for low-, one for high-).

• Each FEM reads out 45 ROCs, or 90 degrees.– Need 4 FEMs/chamber; 8 per arm.

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Connecting it to MUIDLL1• PC not a part of the trigger, but 4 bits per ROC are available.• From previous slide we have 45*4=180 bits per FEM. • This fits on two 6XBCLK fibers.

– Need a New Trigger Board (one per FEM) but the pieces are all literally copies of what is on a MUID ROC.

• An entire arm (16 fibers) would fit onto one Generic LL1 Board

PC FEM8/arm

New Trigger Board8/arm

6XBCLKGeneration

MuMUX6 FPGA

G-Link Daughterboard

BCLK

Data (1)45*2 bits MuMUX6

FPGAG-Link

Daughterboard

Data (2)45*2 bits

Generic LL1 Board

Accepts all fibers for one arm

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Timing?

• Up to now this talk has had no mention of using timing info.

• If it is really needed I don’t think the PC FEE option works.

• One possibility may be to use MUID FEE with a modified ROC.

• The signals would go through some (new) appropriate preamp and discriminator.

• They would be gated on a signal derived from BCLK with width and delay programmed to gate in only collision-related signals.

• The simplest solution would be to use 96 channels/ROC. Then all the rest of the system could be used unchanged.

48 Channels per PC DMU

BCLK w/ programmable width, delay

Signal i

Signal i+1

Signal i+2

Signal i+3

Signal i+4

Data FIFO

BCLK w/ programmable width, delay

Signal i

Signal i+1

Signal i+2

Signal i+3

Signal i+4

BCLK w/ programmable width, delay

Signal i

Signal i+1

Signal i+2

Signal i+3

Signal i+4

BCLK w/ programmable width, delay

Signal i

Signal i+1

Signal i+2

Signal i+3

Signal i+4

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Modified MUID FEE• The solution on the previous slide represents 9

FEMs/arm, which is probably somewhat expensive, and is overkill for two reasons:– Bandwidth limits (conversion time and DCM

communicaiton) allow us to have many more signals/ROC.– We don’t need to send all the accepted event bits to the

trigger – only 1/12 with the suggested numerology.• Various limitations suggest a maximum of 288

channels/ROC.– This would reduce the requirements to 2 FEMs/arm.

• Necessary development for this option:– A scheme to get all those signals onto a ROC.

• New transition cards and passthrough backplane.– A plan for processing all those signals on a ROC.

• Board real estate may be a problem, but reduced complexity (no CFD, no complicated timing adjustment circuitry) may solve this.

– A trigger interface board, as described for PC FEE option. • It could live in the MUID FEM crate.

– Relatively minor mods to the FEM firmware.