FVTX Trigger Toru Nagashima, Yomei Fukushima (Rikkyo University) Shoichi Hasegwa (J-Parc) Itaru Nakagawa RIKEN and FVTX Group 1

MOTIVATION 2

CMS Reported “Ridge” feature in pp,pA Slide from Wei Lei, Rice University 3

High Multiplicity Events is the key! 4 I High multiplicity trigger in FVTX is to be developed for Run15! Slide from Wei Lei, Rice University

ExperimentpA, dApp CMS ✔✔ ATLAS ✔ PHENIX ✔ 5

PPG161 PPG Chair: Shengli Huang (Vanderbilt) PPG Members: PPG Members: John Chin-Hao Chen(RBRC), ShinIchi Esumi(Tsukuba), Jiangyong Jia(Stony), Anne Sickles(BNL), Julia Velkovska(Vanderbilt), Paul Stankus (ORNL) In preparation for PRL 6

Observed v2 in dAu Minimum bias : pp 7 Elementary process (not flow)

He3-Au V 2 MPC South MPC North RIDGE is observed for centrality < 20% in MPC 8

Key Features to observe Ridge 0 ~ 5% centrality => 20 ~ 40 tracks / rapidity unit 80 Mevents Cental dA Events in Run8 9

BBC High Multiplicity Trigger for HeAu 10

Why not BBC High Multiplicity Trigger works on pp? 11 Number of Tracks in PC BBC Charge Ridge Doesn’t show strong correlation between BBC and central arm activities HeAu200 GeV pp Clear correlation btwn central arm activities and BBC multiplicity -> Works as trigger -> Doesn’t Works as trigger

Trigger sensitive to high multiplicity Central arm : trigger on the number of 2x2 fired cells in the EMCal -> interfere with other electron trigger. FVTX Trigger (in preparation) 12 FVTX trigger is the best if (mini-QGP) is seen in FVTX rapidity region. So far the best trigger for central arm high multiplicity in pp. (Need correlation study between FVTX and Central arm.)

Required Rejection Power # of Tracks / arm > 0> 10 > 20> 30> 40 Fraction in MB 100%10%0.7%0.04%0.008% Rates in MB 1MHz100kHz7kHz400Hz80Hz Required Rejection Power ,50012, # of Tracks in FVTX / 510GeV pp Run13 Data Possible band width for FVTX Trigger

Key Features to observe Ridge 0 ~ 5% centrality => 20 ~ 40 tracks / rapidity unit 80 Mevents Cental dA Events in Run8 14 FVTX North and South separate trigger bits 100Hz per arm (Total 200Hz) 200Hz x 3600s x 24h x 7days x 9 weeks x 30% DAQ time ~ 300M high multiplicity events Goal of Run 15 - > Purity of the trigger is the issue

FVTX TERMINOLOGY AND FVTX TRIGGER 15

Debugging BNL Test Bench September,

FVTX Wedge 17

18 At least one hit in 3 out of 4 stations is required within a half sector ((  =7.5 o ). -> TrackFlag. If there are more than two tracks within a given sector (  =15 o ), the second one won’t be counted. We Request Two Trigger bits (one per arm) for FVTX trigger. AND Limited to 1bit

FEM -> FEM-IB Cable 19 About 30 cm long.

FEM Board 20 Test Pin OUT Serial Wire To FEM-IB Test-Pin

21

FEM -> FEM-IB Installation 22 November 5 th, 2014

FVTX Terminology 23 Station-0 Station-1 Station-2 Station-3 Wedge Sector Wedge FEM Cage

FVTX Trigger Parameters 24 Station-0 Station-1 Station-2 Station-3 Wedge Sector Wedge FEM Cage # of hits/wedge # of active wedges out of 4 stations Active Sector (AND/OR) # of active FEMs Arm Active Cage (AND/OR)

Trigger Concept Multi Track Multi Hit How well we can trigger multi track events by multi hit algorithm? 25 Trigger used in CMS

Multi-Track and Multi-Hit Triggers 26

Parameter Conditions for this study 27 OR

Run Information Run GeV pp Run# DAQ Time48 minutes Raw BBC Rate1.2MHz Scaled BBC Rate51 Hz Total MB Samples147k events

MULTI-TRACK TRIGGER ALGORITHM #of Active FEMs = 6,9,12 / cage

Multi-Track Mode (South) Number of Tracks/arm Number of Hits/arm Number of active FEMs >=6 / cage

MULTI-HIT ALGORITHM

MultiHit (South) # of Active Cage > =6

Multi-Track vs. Multi-Hit Algorithm MultiTrack MultiHit Low track events are more suppressed in Multi-Track than Multi-Hit Mode

# of Active Cage >= 9

FVTX Trigger Performance

Conclusion Turn on is good against the hit multiplicity, but cannot avoid low #track leak for the track multiplicity. So far, satisfactory rejection power and efficiency is not achieved in data analysis. Further study to be made to seek for better performance. If RP isn’t sufficient, the trigger needs to be prescaled. However, the FVTX trigger still provides orders of magnitudes more high multiplicity samples than MB. 40

DIFFERENCE BETWEEN ONLINE AND OFFLINE TRACK 41

Difference in Track Criteria This track will be recognized as track in both online and offline. A FEM track frag Offline track FEM i B C B This category won’t be picked up by the trigger -> cause of survival tracks

Difference in Track Criteria This track leaves only 2 hits in FVTX and won’t satisfy ¾ station criteria in the trigger A FEM track frag Offline track FEM i B C C

Difference in Track Criteria This differences can cause small fraction survives FEM track frag> x trigger condition A FEM track frag Offline track FEM i FEM i+1 B C A C C -> B This category won’t be picked up by the trigger -> cause of survival tracks Possibly remove the border within FEM FPGA

FVTX Alignment y-axis x-axis FVTX Event Display track

St-0 St-1 St-2St-3 Wedges are slightly staggered in phi direction to gain phi resolution on purpose This mismatch of phi angle between stations enhances “category C”

Low # Track Leak Cause Summary 1.Online trigger won’t recognize track which crosses boarder between sectors 2.Online trigger won’t have VTX hit information. 3.FVTX stations are staggered by a little bit in phi direction 47 No trivial solutions without significant revise in hardware configuration

BACKUP 48

He3-Au: BBC Charge vs. #Track in PC Number of Tracks in PC BBC Charge Ridge 49 - > About 20 tracks in PC in the centrality < 20% in HeAu

Multiplicity vs. rapidity 50 PHOBOS Phys. Rev. C72, d-going Au-going v2v2 smaller Larger

Multiplicity vs. rapidity 51 He3-going Au-going v2v2 smaller Larger He3Au ~ 60 ~ 25 On average ~40 tracks is a guideline to observe v 2

Run15 pp Goal FVTX North and South separate trigger bits 100Hz per arm (Total 200Hz) 200Hz x 3600s x 24h x 7days x 9 weeks x 30% DAQ time ~ 300M high multiplicity events (80 Mevents Cental dA Events in Run8) 52