# Presentation: 518701

## Trigger Performance Studies and Data Analysis

**Trigger Performance Studies ****and Data Analysis**

**PHENIX Muon Trigger Upgrade Review, September 25, 2008**

- Matthias Grosse Perdekamp, Illinois

- (I) Overview:
-          Physics Goal
-          Experimental Challenges
-          Upgrade Scope
- (II) Trigger Rejection
- (III) Technology Choice and R&D
- (IV) Offline Analysis

## (I) Overview -- Physics Goal

- Measure inclusive single longitudinal spin asymmetries in
- polarized proton-proton collisions to determine quark and
- anti-quark helicity distributions:

- Clean theoretical link:  inclusive lepton asymmetry  PDFs
*Single spin asymmetries with weak bosons at RHIC *
*P.M. Nadolsky, C.P. Yuan, Nucl.Phys.B666:31-55,2003*
-  Event generator: RHICBOS

## (I) Overview -- Experimental Issues

- (A)  Select W-events from 9.6 MHz p-p collisions (level 1 rejection > 10000)
-        Challenges   Decay muon backgrounds
-                             Beam backgrounds
**Offline ******** Analysis Issues**
- (B)  Assign events to W- or W+ asymmetry: ALμ- and ALμ+
-        Challenge     Tracking: charge separation for pT > 20 GeV
-   Link W-events to correct bunch crossing (beam polarization!)
-        Challenge     Timing better than 100 ns
-   Eliminate backgrounds in inclusive lepton data sample
-        Challenges  Physics backgrounds: charm, botton, Z0
-                                Tracks with falsely reconstructed high pT
-                                Cosmic ray background

## (I) Overview: Upgrade Scope

- RPC1(a,b)

- RPC3

- RPC3

- muID
- north

- muID
- south

- muTr south

- muTr north

- muTr-trigger

_**Existing Muon Arms:**_
- o muID (triggering)
- o muTr (tracking)
- o trigger rejection
-    ~ 200 - 500

- _Trigger Upgrade:_
- o remove low pT muons from hadron decay  tracking
- o reject beam backgrounds + tag polarization information  timing
-              instrument muTr with trigger boards that send tracking I
-                  info to level 1 trigger processors

_**Upgrade:**_
- o muTr trigger electronics: muTr 1-3   send tracking info to level-1 trigger

- o RPC stations: RPC 1+3                    tracking + timing info to level-1 trigger
-    note: RPC1 has larger acceptance than RPC3 at large radii, RPC1+ RPC3 give best
-     timing coverage. RPC1+10 cm absorber (but not 30cm) can be installed simultaneously.

_** **__**Trigger idea:**_
-  Reject low momen-
-  tum muons
-  Cut out-of-time
-  beam background

## (I) Overview: Installation Schedule

- _Trigger Upgrade:_
- o remove low pT muons from hadron decay  tracking
- o reject beam backgrounds + tag polarization information  timing
-              instrument muTr with trigger boards that send tracking I
-                  info to level 1 trigger processors

- Shutdown            muTr-trigger         RPC                    Absorber
-                              electronics
-     2008                north: 1+2+3        south:                  south:
-                                                          2 half octants      octant prototype
-                            south: 2 octants
-     2009               south: 1+2+3        north: RPC3         north: 30 cm absorber
-                                     -----------north ready for first W-physics----------------
-     2010                                            south: RPC3        south: 30 cm absorber
-                                                    -----------north ready for first W-physics----------------
-     2011                                            RPC1                   30  10 cm absorber

- Muon Trigger Project

- Before the arrival of the forward vertex
- detector (FVTX) in 2011 an absorber
- will be necessary to suppress off-line
- backgrounds.

- absorber plans will be decided based on test results + schedule for W-physics

## (II) Trigger Rejection -- Collision                  			Related Backgrounds

- RPC1(a,b)

- RPC3

- muID
- north

- muTr south

- muTrig1-3

- _Trigger Upgrade:_
- o remove low pT muons from hadron decay  tracking
- o reject beam backgrounds + tag polarization information  timing
-              instrument muTr with trigger boards that send tracking I
-                  info to level 1 trigger processors

_**Collision related backgrounds:**_
-    GEANT based studies of
-    trigger rejection and efficiency
-    Signal: Pythia  106 W-events
-    Background: Pythia  106 min. bias events
-  Trigger algorithm:
-  (1)   *RPC1 || muTrig1 x muTrig2 *
*        **x muTrig3 x RPC 3 x muID*
*        **** **Δ**strip≤ 3*
* *
* *(2)   *Δ**Φ**=**Φ**1**-**Φ**muTrig3**≤2,3* degrees
-  Noise: 1kHz for each muTr strip           Absorber: 0,10 or 30 cm of *Cu*
-             10Hz/cm2 in the RPCs

## (II) Trigger Rejection -- Collision                  			Related Backgrounds

-    **Station 1 setup               Absorber                Trigger Rejection**
**                                                                          ****Δ****Φ****= 2   ****ΔΦ****= 3 degrees**** **
**   ****muTrig1 + RPC 1              0 cm                    18000    12000          **
**   ****muTrig1 + RPC 1            10 cm                    35000    26000    **
**   ****muTrig1                           30 cm                    65000    50000**

- Trigger rejection above the required factor 10000.
- Absorber increases rejection significantly but is not
- required for triggering.

## (II) Trigger Rejection & Efficiency vs Detector Alignement

***RPC1 || muTrig1 x muTrig2 x muTrig3 x RPC 3 x muID, ******Δ******strip≤ 2, *****10cm absorber**

- Rejection

- Efficiency

- pT [GeV]

- misalingment in degrees

**x10****3**** ****  **

- 0.00     Perfect alignment
- 0.02     degree RPC1 rotated
- 0.03                 “
- 0.04                 “
- 0.25                 “

- Misalingment: Robust rejection, sensitive efficiency
-                         alignment to 2mm in RPC1 to 5 mm in RPC3

## (II) Trigger Rejection -- Beam                 			Related Backgrounds

- (II) Trigger Rejection -- Beam                 			Related Backgrounds

- Estimate of high momentum beam
- background based on muID triggered
- data (with and without collision trigger)
- at pbeam=100 GeV and L=1x1031cm-2s-1:
- There are 60Hz of beam related tracks
- with a longitudinal momentum
- pz > 10 GeV/c.
- Scale to pbeam = 250 GeV and
- L=16x1031cm-2s-1  240 Hz
- (or 25% of the intended bandwidth)

- BBC collision trigger do not remove high momentum beam background since we will have  an average of 1 collision/crossing at L=1.6x1031cm-2s-1

## (II) Trigger Rejection -- Beam                 			Related Backgrounds

- Clock
- Forward
- Forward+CollisionTrigger
- Forward+Single Muon

- Time of
- incoming
- beam

- Time of
- collision
- products

- Measurement of the beam back-
- ground time structure during run
- 2004 using forward scintillators at
- the location of RPC-3, the single
- muon and the collision triggers:
- A gate of +/-10ns on the RPC time
- (3ns timing resolution) reduces
- beam backgrounds (all momenta)
- by about a factor 20 and appears
- more efficient than the collision
- trigger in removing background.
- For high momentum background
- tracks the rejection is 2 if the high
- momentum  beam background
- travels with equal probability with
- either the incoming or outgoing
- beam bunches  120 Hz or smaller
- (less than 15% of the bandwidth)

- RPC
- gate

- Measure/”define”  rate
- < 500 Hz/cm2 (x10 safety)

## (III) Technology Choice and R&D

| Requirements | CMS Bakelite RPCs | Glas RPCs | Scintil-lators | Cathode Strip Chambers |
| --- | --- | --- | --- | --- |
| Rate=500 Hz/cm2 | >1kHz/cm2 | - | + | + |
| timing~3ns | ~1.5 ns | + | + | - |
| Radiation hardness | LHC!! | + | + | + |
| Cost + Production | GT/KODEL | - | - | - |
| Integration | Compact
Half octants | - | + | + |

- CMS bakelite technology
- developed for muon trigger
- applications at the LHC.

- CMS specs exceed
- PHENIX specs!

- Korea University is
- PHENIX collaborator!

## (III) Technology Choice and R&D

- Plan:     Adapt CMS technology so that CMS R&D results. For
-              example, we insist on identical materials and construction
-              procedures to make sure the radiation hardness studies
-              are still valid.
- Goals:  (I) analyze and understand CMS bakelite RPC technology
-             (II) develop PHENIX front end electronics for RPCs
-            (III) develop and optimize detector production and assembly
-            (IV) grow RPC expertise necessary to deploy and operate
-                   the detectors successfully.

## (III) Technology Choice and R&D

- GSU                    detector construction, RPC performance, Q&A (A,C)
- CIAE      	  develop detector box, signal plane, support structure  (C)
- UIUC                   2-d efficiencies, rate capability, gas mixture (“open” RPC)
- BNL                     assembly, Q&A (using prototypes C and D)
- Colorado              test readout electronics on RPC (using prototype C)
- Nevis                   develop front end electronics

- Generation 1-5     GSU prototypes, PKU prototype, open UIUC prototype
- Prototype A          3 detectors built at GSU with gas gaps from KODEL
- Prototype B          original CMS barrel detector gaps and signal planes
- Prototype C          3 RPC3A detector modules: full production chain
- Prototype D          3 half octants of RPCs: full production chain
- RPC-1 Prototype  RPC-1 octant: full production chain, test “split gaps”

## (III) Technology Choice and R&D :              						Prototypes C and D

**Scintiallator Trigger Hodoscope**

**10 shelves for RPCs up to 640 channels**

**Scintillator Trigger Hodoscope**

**NIM crate with DAQ**

**3 PHENIX RPC TDCs within crate**

- (III) Technology Choice and R&D :              						Prototypes C and D

- Past: establish assembly and Q&A procedures for RPC 3
- Next: establish 2-d efficiency measurements as outgoing Q&A
- Last week: first complete chain of prototype D + PHENIX FEE!

## (III) First results from Prototype D       with PHENIX FEE

**Noise rate:**
**RPC H.V = 9.4 kV**
**PHENIX RPC FEE Threshold = 200 mV**

- Noise Rate (Hz/cm2)

**RPC test stand event display**

**cosmic ray trigger scintillators**

**RPC readout strip planes**

**cosmic ray trajectory**

**RPC H.V = 9.7 kV**

- (III) First results from Prototype D       with PHENIX FEE

- Cluster size vs
- threshold

- Efficiency vs
- threshold

## (III) 2-D Efficiencies + Rate Capability at UIUC

-      Two 0.6 Ci Fe55 sources are attached on one side of the RPC. This creates a photon background from 10kHz on one side to 10 Hz on the other. We then study the efficiency for cosmics as function of position that is background rate!

- Timing Scintillators

- Drift Chambers (resolution ~ 1 mm)

- RPCs

- track cosmics
- and study RPC response

## (III) Rate Capability in Bakelite RPCs)

- ~ 9 kHz

- ~ 0.5 kHz

- ~ 0.05 kHz Glass RPCs

- Fe-source

- (III) Rate Capability in Bakelite RPCs)

- ~ 0.2 kHz PHENIX  req.

- Up to  500 Hz/cm2
- with uncoated bakelite.
- Linseed oil surfaces are
- under study.

- 2-d-efficiencies

- Efficiency scale

- Fe-55 *γ*
- background
- level

## Training & Education

| Bassett, Dan | UIUC |
| --- | --- |
| Bayse, Austin | ACU |
| Burnap, Alexander | UIUC |
| Deinlein, George | UIUC |
| Goldberg, Leah | Illinois Weslyan College |
| Johnson, Paul | UIUC |
| Jumper, Daniel | ACU |
| Kim, Hye Ryong | UIUC |
| Kim, Yongsun | UIUC |
| Kish, Jay | ACU |
| Lee, Chang | UIUC |
| Lichtenwalner, Phil | Muhlenberg |
| Mucia, Nicholas | UIUC |
| Natoli, Tyler | UIUC |
| Rao, Gaurav | UIUC |
| Sparks, Nathan | ACU |
| Strack, Jason | UIUC |
| Tech, Sebastian | Dortmund |
| Veicht, Aaron | UIUC |
| Watts, Cole | ACU |
| Wood, John | ACU |
| Wright, Ryan | ACU |

**2 graduate students now**
**working at BNL on RPCs!**
**undergraduate students**
**sofar in the RPC Lab:**
- 14 UIUC
- 6 ACU
- 1 Muhlenberg College
- 1 Illinois Weslyan
- 14 DNP-CEU posters sofar
**Faculty summer visitors:**
- Rusty Towell, Don Isenhower,
- Brett Fadem

## (IV) Offline Analysis

**The Issue with the non-hermetic detector**
**Backgrounds:**
-             Physics:  heavy flavor quarks, Z0
-             Cosmics: high momentum cosmic ray muons that travel
-                             through the muon spectormeter and pass also
-                             close by the interaction vertex.
-             Mis-reconstruction of the lepton charge sign for high
-             lepton momentum  diluation of asymmetries.
-             Fake high pT tracks
**Asymmetries:**
-             Event generator  GEANT Detector Response
-         Reconstruction  Asymmetry Calculation

## Non-Hermetic Detectors

- RHIC detectors are not fully hermetic...
- electron and muon acceptance of the RHIC detectors varies strongly over the rapidity range...
- Thus:
- missing transverse energy cannot be used to clean up the W signal
- Trigger has to rely exclusively on high *p*T electrons and muons
- The backgrounds to the W from Z*→**e/**μ* and QCD/fakes may be significant
- enough Z-statistics for measurement/tuning of corrections?
- Detailed simulations will be crucial to determine acceptance corrections, efficiencies, and backgrounds
- limited Z acceptance makes tuning of the simulations with Z*→**ee/**μμ* more difficult

- M. Rijssenbeek at Parity Violating Spin Asymmetry Workshop

## a “Non-Hermetic” Detector: UA2 – vs.1

- Central tracking + Preshower + EM Calorimetry; |*η*|<1
- Forward spectrometer + PS + EM Calorimetry; 1<|*η*|<3

- a non-hermetic detector...

- UA2 collaboration: M Banner *et al.*, Phys. Lett. 122B (1983) 476.
- UA2 collaboration: P Bagnaia *et al.*, Phys. Lett. 129B (1983) 130.

- M. Rijssenbeek at Parity Violating Spin Asymmetry Workshop

## (IV) Offline Analysis:                             Non-Hermetic Detectors

- (I) W-analysis (with a non-hermetic detector):
-              Observable: cross sections and asymmetries for inclusive
-                                   high pT leptons
-              1. use cross section analysis to make sure that
-                  backgrounds are understood (Z and W)
-                   tune detector Monte Carlo description
-                   understand backgrounds
-                   tune cuts for background rejection
-                       [cross sections are know from theory
-                        and previous experiment]
-               2. asymmetry analysis based on MC and background
-                   studies from cross section measurement.
-               3. extract quark helicity distributions from QCD analysis
- Topical workshop: W. Vogelang,  M. Grosse Perdekamp, B. Surrow, Workshop on Parity Violating Asymmetries at RHIC, _[http://](http://thy.phy.bnl.gov/~vogelsan/alws/agenda.html)__[thy.phy.bnl.gov/~vogelsan/alws/agenda.html](http://thy.phy.bnl.gov/~vogelsan/alws/agenda.html)_, BNL, April 26+27, 2007.

## (IV) Offline Analysis

**The Issue with the non-hermetic detector**
**Backgrounds:**
-             Physics:  heavy flavor quarks, Z0
-             Cosmics: high momentum cosmic ray muons that travel
-                             through the muon spectormeter and pass also
-                             close by the interaction vertex.
-             Mis-reconstruction of the lepton charge sign for high
-             lepton momentum  diluation of asymmetries.
-             Fake high pT tracks
**Asymmetries:**
-             Event generator  GEANT Detector Response
-         Reconstruction  Asymmetry Calculation

## (IV) Physics Backgrounds: c,b,Z0

- Hadronic decays dominate muon rates
- W dominate only above 20-25 GeV
- Charm and Bottom do not play a role
- Z0 can be treated as a dilution of 10-15%. It’s contribution is calculable and can be estimated by Z0 that decay into muon pairs.

- (IV) Physics Backgrounds: c,b,Z0

## (IV) Cosmic Ray Backgrounds

-     with a 6 week long cosmic ray run in 2007:
-     pT > 20GeV/c and distance of
-     closest approach < 5 cm          0.0098 Hz
-     Look on both sides:  x 10
-     RPC timing cut:  x 10 (direction, 20 ns gate)
-                                                     9.8x10-5 Hz
-     In 30 week run with 30% duty factor  530 cosmics

## 2007 Cosmic Ray Run with PHENIX Muon Arms

**p**

**p****T**

**r****vtx**

**z****vtx**

**charge**

**eta**

## (IV) Charge Sign Mis-Identification

- Example charge sign
- reconsturction for position
- resolution of 300um:
- Charge sign correctly
- reconstructed for ~96%
- at *p**T**=40 GeV* and ~88%
- of the muons with a
- reconstructed pT of
*p**T**= 80 GeV/c*
- The absorber has no
- significant impact.

## Generated vs Reconstructed Momentum 

- For position
- resolution of
- 300 micro meter
- MTU group has
- started work on
- muTr alingment
- system to improve
- the position
- resolution.

## (IV) False High pT Background

- (IV) False High pT Background

- Example Kaon Decay: 1-2 GeV/c and 2-3 GeV/c

- Background:
- Low momentum punch
- Through hadrons decay
- In the muon magnet to mimic
- A high momentum track!
- Signal to Background
- without absorber
-       S:B ~ 1:3
- Signal to Background
- with absorber
-       S:B ~ 3:1

## (IV) Reconstructed Asymmetries

- Without smearing
- 300pb-1 and 1300pb-1
- RHIC I          RHIC II
- With smearing

## Summary

- o We have carefully studied the performance of the future
-    PHENIX muon trigger and the possibility to measure
-    quark and anti-quark helicity distributions through inclusive
-    lepton asymmetries in W-production. We find:
- o The trigger rejection is in excess of 10000
- o CMS bakelite RPC technology was specifically developed
-    for muon trigger application in hadron colliders and is by far
-    the best technology choice.
- o A Monte Carlo study shows that the expected asymmetries
-    after taking into account all backgrounds have good sensitivity
-    for the quark helicity distributions.