Current Status of the VTX analysis and the DCA measurement

Current Status of the VTX analysis and the DCA measurement
Takashi HACHIYA RIKEN 2012/3/8 PHENIX Colaboration FSU.

PHENIX Colaboration Meeting @ FSU.
Contents The method of DCA measurement with VTX Current status of Geometry Calibration CNT based Tracking DCA measurement Reaction Plane Measurement Summary 2012/3/8 PHENIX Colaboration FSU.

VTX Software Team Person Working On Yasuyuki Akiba Supervise Sasha Lebedev Organize the software team and the strip software Mike McCumber SATrack and Tool development Matt Wysocki Kalman Filter module Ryohji Akimoto SATrack and Primary Vertex Measurement (as yesterday presented) Hidemitsu Asano Geometry calibration and Beam Center Maya Shimomura Geometry calibration Mikhail Stepanov Maki Kurosawa BG estimation Aneta Iordanova Embedding module John Chin-Hao Chen Hot&Dead for Strip and Online Monitor in Run 12 Hiroyuki Sako Hot&Dead for Pixel Lei Ding BG estimation, H&D and geometry calibration (as yesterday presented) Alex Shaver dE/dx calibration Jason Bryslawskyj Fast production in run12 Rachid Noiucer Hot&Dead for the Strip Takashi Hachiya CA based Tracking, Hot&Dead for pixel, Fast production in run12 2012/3/8 PHENIX Colaboration FSU. If I miss people in the list, I am sorry

For the DCA measurement
Clustering sensor 3D position on PHENIX coordinate (Geometry calibration) Particle ID Use not only VTX, but Central Arm (RICH, EMCAL, TOF). Tracking B3 B2 B1 B0 connecting clusters for tracking Primary Vertex DCA Measurement 　　 Charm / Bottom separation All information is needed 2012/3/8 PHENIX Colaboration FSU.

Track reconstruction method
We have two methods Standalone Tracking method Only VTX information is used Large detector coverage & worse momentum resolution Used for Primary Vtx & RP Measurement It might be possible to measure DCA in p+p CNT based tracking method DCH track is used as a guide and associated with VTX Clusters Acceptance is limited by Central Arm Better momentum resolution Used for the DCA measurement in Au+Au (p+p) B3 B2 B1 B0 VTX 1 VTX DC+PC RICH TOF EMCAL Central Arm 2 DchTrack 2012/3/8 PHENIX Colaboration FSU.

Geometry Calibration People Maya SHIMOMURA, Hidemitsu ASANO, Mikhail STEPANOV, Lei DING, Maki KUROSAWA, Takashi HACHIYA and Yasuyuki AKIBA We have a local meeting dedicated for the alignment twice a week. Organized by Maya and supervised by Yasuyuki. 2012/3/8 PHENIX Colaboration FSU.

Geometry Calibration Calibration Parameters Beam Center Calibration VTX West and East Central Arm Alignment of the Ladder by Ladder position. Iterative procedure of the alignment Starting from the survey geometry. 1)  2)  1)’ 2)’  1)’’  2)’’… Two alignment methods External method using CNT track (Main method) Internal method for consistency and outside CNT acceptance Alignment in phi and z separately. 2012/3/8 PHENIX Colaboration FSU.

Beam Center Calibration with the VTX
Beam center is used as a starting point of the alignment φb:angle of track in X-Y plane φb=atan 𝑦1−𝑦0 𝑥1−𝑥0 (x0,y0) hit at B0 (pixel) (x1,y1) hit at B1 (pixel) DCA from (0,0) X Y Beam center (Xbeam,Ybeam) L0 L1 DCA(cm) b 0.4 0.2 0.0 -0.2 -0.4 DCA = Ybeam*cosφb - Xbeam*sinφb fit function From the fit, (xbeam, ybeam) is determined Similar beam center calibration for the CentralArm(DC) 2012/3/8 PHENIX Colaboration FSU.

Geometry Alignment in phi
The external method is used for the phi alignment Consistency check with the internal alignment Residual is aligned at zero in dphi for all ladders (all layers, all ladders) This took a large effort by Hidemitsu, Maya, Mikhail, but it is finally converged B3 B2 B1 B0 dphi3 dphi2 0.4 dphi0(cm) -0.4 0.0 dphi0 distribution Before the alignment After alignment 0.2 0.2 0.0 0.0 -0.2 -0.2 (plot from MAYA) 2012/3/8 PHENIX Colaboration FSU.

Geometry Alignment in Z
The external method is also used for the Z alignment. First, Lei reported that the Z positions of ladders are not aligned. Hidemitsu performed the Z alignment Current status, Final iteration is running. We will finish soon Before alignment B0 West B0 East Ladder # dZ mean (cm) After alignment B0 West B0 East Ladder # dZ mean (cm) From Hidemitsu’ Slide From Hidemitsu’ Slide 2012/3/8 PHENIX Colaboration FSU.

Geometry Calibration Summary
We developed the method to align the global offset between VTX and Central Arm. 1st version alignment is completed Beam Center and the offset Phi alignment Z alignment Next Step Confirm that the alignment is unchanged for other runs Beam center calibration (run-by-run)  Ready for the VTX production 2012/3/8 PHENIX Colaboration FSU.

Primary Vertex Measurement
3D primary vertex is determined using SA tracks event by event basis presented by Ryohji Result Clear correlation in Z(VTX) vs Z(BBC) Beam Profile is seen in X-Y vertex Beam Width is 85um. Y-VTX vs X-VTX Y-VTX distribution Z(VTX) vs Z(BBC) X(VTX) (cm) Y(VTX) (cm) BeamSize -0.1 0.0 0.2 0.1 -0.2 1mm 10 1mm = 85um Z(VTX) (cm) -10 Y(VTX) (cm) 2012/3/8 Z(BBC) (cm) PHENIX Colaboration FSU.

Primary Vertex Resolution
West – East in X West – East in Y West – East in Z 600um 300um 300um 49.6um  24.8um 150um  75um 89um  45um 39.7um (sim) 29.2um (sim) 48.8um (sim) (cm) (cm) (cm) Resolution is evaluated using the difference of the primary vertex for the VTX West and East. 𝜎 West = 𝜎 East = 2 ∙𝜎 Total if assuming Ntrk is half. 𝜎 Vwest – V east = 𝜎 West 𝜎 East 2 =2 ∙𝜎 Total These values are similar with that in simulation shown in Ryohji’s slide. Z alignment is not finished yet 2012/3/8 PHENIX Colaboration FSU.

CNT based Tracking Algorithm DCA distribution DCA resolution Centrality dependence and pT dependence 2012/3/8 PHENIX Colaboration FSU.

Algorithm : Track Association to VTX hit
CNT track Actual Track B3 B2 B1 B0 dphi range dphi3 dphi2 Algorithm : Track Association to VTX hit Use CNT track as a seed. Search for the associated hit at the outer layer. loose cut for large DCA Search for the next associated hit using the residual correlation. Choose the “Good” associated hits using the least chi2. dphi3 vs dz3 dphi3 (cm) dz3 (cm) 1cm dphi3 (cm) dphi2 (cm) 5mm 1mm 𝜒 2 = 𝑑𝑝ℎ𝑖′ 𝜎 𝑝ℎ𝑖 𝑑𝑧′ 𝜎 𝑧 2 𝑑𝑝ℎ 𝑖 ′ =𝑑𝑝ℎ 𝑖 𝑖 −𝑑𝑝ℎ 𝑖 𝑗 𝑑 𝑧 ′ =𝑑 𝑧 𝑖 −𝑑 𝑧 𝑗 2012/3/8 PHENIX Colaboration FSU.

Center of B bending Track vector DCA0 DCA calculation 1) DCA0 calculation DCA0 is calculated using track vector at B0 hit Track is bent by B-field. Based on the vector, track trajectory is calculated as a circle. DCA0 is calculated. 2-1 DCA0 can be improved using the outer layer hit 2-2 DCA0 can be improved by refitting with Kalman Filter method Matt is working Associated cluster is kept in the DST. 2) Further improvement of DCA (in progress) DCA0 DCA Measured vector at DCH DCH B0 True track vector B3 l3 l0 2012/3/8 PHENIX Colaboration FSU.

DCA distribution (Au+Au 200GeV MB)
DCA (pT>1GeV) DCA (pT>1GeV) Nhit>=3hits B0, B2, B3 is required |dz3|<0.5, |dphi3|<0.5 Chi2(dphi)<3 For electrons N0>2 && E/p>0.5 DCA is calculated using primary vertex (event by event). All hadrons Electrons E/p (0.7<p<0.9GeV/c) DCA distribution Fit by Gaussian All hadrons: 72.4um  0.3um Electrons: um  14.3um It seems that electrons have wider distribution than hadrons. But… need more statistics. (60k events are analyzed) All track N0>2 Background 2012/3/8 PHENIX Colaboration FSU. B0 hit is required

Centrality Dependence of DCA (pT>1GeV/c)
60-92% 40-60% 20-40% 5-20% 0-5% 819um 843um 811um 811um 822um Fit with gaussian + pol2 (BG) Gaussian sigma is shown. The width looks no centrality dependence. 60k events are analyzed (1 PRDF) Nhit>=3hits B0, B2, B3 is required |dz3|<0.5, |dphi3|<0.5 Chi2(dphi)<10 (loose cut) For electrons N0>2 && E/p>0.5 2012/3/8 PHENIX Colaboration FSU.

pT dependence of the DCA (MB)
153um 117um 98um 86um 78um 68um Nhit>=3hits B0, B2, B3 is required |dz3|<0.5, |dphi3|<0.5 Chi2(dphi)<10 (loose cut) For electrons N0>2 && E/p>0.5 The width is narrower with higher pT. 60k MB event is analyzed. 2012/3/8 PHENIX Colaboration FSU.

pT dependence of DCA width
Data Simulation pT(GeV/c) (um) DCA resolution between data and simulation is compared. DCA resolution = Gaussian sigma Simulation : Alan’s Talk at Review (values are taken by eye from his slide) pT dependence looks similar, but the resolution in the data is slightly worse. In data, Prim. Vtx. resolution is also included (~30um) . 2012/3/8 PHENIX Colaboration FSU.

p+p analysis in Run 12 We take p+p 200GeV data in Run12 10% data is reconstructed to the DST in the fast production Calibration Hot & Dead Map for both pixel and stripixel Geometry alignment Quick analysis First Result from the quick analysis with the DST Beam profile is wider DCA width is 107um (Run11 alignment is used) DCA(pT>1GeV/c) y-vtx(cm) 1mm 1mm x-vtx(cm) 2012/3/8 PHENIX Colaboration FSU.

Background Estimation using the event mixing
Small Angle Rotation method Event mixing in the same event to evaluate the background from the random association. Random association is sensitive to the local particle density (JET and flow). CNT track is rotated  5 degrees in theta and phi direction randomly. The rotation method looks reasonably working Maki and Lei are working on this. Lei showed yesterday dphi3 at B3 Outer most pixel layer 5 cm  5 deg CNT track 5mm Real track Rotated track 2012/3/8 PHENIX Colaboration FSU. dphi3(cm)

Reaction Plane Measurement with VTX
Reaction Plane is measured by VTX clusters and SATrack. All 4 layers are used. Both re-centering and flattening is performed The RP resolution of the VTX cluster is RP2=0.35 This is much better than the BBC and comparable with the RxnP detector We plan to store the 1st to 6th RP in the DST. It is useful for Vn analysis Reaction Plane is studied by Tsukuba Students: Hiroshi Namagomi and Satoshi Horiuchi supervised by ShinIchi Esumi n=2 0.4 0.2 0.0 -0.2 VTX cluster N-S BBC RP2 = <cos n(i - j)> <sin n(i - j)> Centrality C P 2012/3/8 PHENIX Colaboration FSU.

Toward Physics In order to obtain the Physics result until QM2012, we start the discussion, at the VTX software meeting, about what we complete Organized by Yasuyuki Akiba. Current Plan We must focus on the RAA and vn of hf-electrons until QM2012. Hf-electron yield in Au+Au and p+p 200GeV Hf-electron v2 in Au+Au 200GeV Tasks Real data analysis Real data QA Simulation analysis … Task list is in Offline wiki (maintained by Yasuyuki) 2012/3/8 PHENIX Colaboration FSU.

Summary Geometry calibration is almost done Aligned in both phi and z direction The code development of CA based tracking is almost done. DCA resolution is 80um There are remaining items After this, DST production will start. Quick p+p analysis in the run 12 is started. Reaction Plane by VTX has a good resolution To Physics, We start the discussion 2012/3/8 PHENIX Colaboration FSU.

Backup 2012/3/8 PHENIX Colaboration FSU.

Parameters of VTX Side view Cutaway view from beam axis
Big Wheel (for Electronics holding and cooling) 2 stripixel layers 2 pixel layers Side view Cutaway view from beam axis Structure : 2 pixel layers, 2 stripixel layers Layer Kind R(cm) Z(cm) # ladder RO Channel Occupancy(Au+Au) X0 Pixel 2.5 10 10 1,310,720 0.53% 1.28% 1 5 20 2,671,440 0.16% 2 Stripixel 11.7 16 16 122,880 4.5% 5.43% 3 16.6 19 24 221,184 2.5% 2011/2/15 Focus Seminar, Takashi HACHIYA

Beam Center and the Offset of the coordinate system
We have 3 coordinate systems DCH coordinate (PHENIX coordinate) for the central arm VTX west and east barrel coordinate systems Geometrically independent each other. VTX coordinate should be aligned to the DCH coordinate (PHENIX) The beam position can be used to adjust these coordinate systems. DCH measures the beam position using the zero field data Alpha angle vs phi in DC VTX measures the beam position using the both zero and full field data DCA vs phi in VTX alpha DCA (cm) phi 2012/3/8 Made by Hidemitsu PHENIX Colaboration FSU. Made by Hidemitsu phi

Beam Center and the Offset of the coordinate system
The beam position can be used to adjust these coordinate systems. VTX measures the beam position using the both zero and full field data DCA vs phi in VTX DCH alignment relative to the beam center DCH measures the beam position using the zero field data Alpha angle vs phi in DC DCA (cm) phi Made by Hidemitsu alpha phi 2012/3/8 Made by Hidemitsu PHENIX Colaboration FSU.

Track reconstruction method
We have two complementary methods Standalone Tracking method Only VTX information is used Large detector coverage & worse momentum resolution Used for Primary Vtx & RP Measurement It might be possible to measure DCA in p+p Central Arm based tracking with VTX Cluster DCH track is used as a guide and associated with VTX Clusters Coverage is limited by Central Arm Better momentum resolution Used for the DCA measurement in Au+Au (p+p) 1 VTX B3 B2 B1 B0 VTX DC+PC RICH TOF EMCAL 2 Central Arm DchTrack VTX p resolution(sim) DC p resolution We have 2 track reconstruction methods. One is the standalone tracking method The other is the DCH based tracking method. In this method, DCH track is used as a guide and associated with the VTX cluster. These methods have good and not good points. Good point for standalone tracking is :to reconstruct the track by Only VTX information. It means all the VTX coverage is available. But on the DCH based tracking, The detector coverage is limited by Central arm region. On the other hand, the momentum resolution of the standalone tracking is worse Compared to the DCH tracks %because the magnetic bending of the track is small in the VTX region. %Now, we have 2 algorithms for standalone tracking. Using those algorithms, %We can get more confident result. %But DCH has good momentum resolution. Bottom figure shows the momentum resolution as a function of pT. %This is calculated from simulation for standalone tracking %and Dch track is from run 2? Data. 2012/3/8 PHENIX Colaboration FSU.

Comment on the Standalone Tracking
We decided not to use the SATrack for the DCA measurement in Run11. After the extensive study of the SATrack using the simulation by Ryohji and Mike, we found that the SATrack with 3 associated clusters is mostly fake. In the high multiplicity environment. Large dead area in the detector. We limit the purpose of the SATrack for Primary vertex measurement Reaction Plane measurement Jet measurement using the track from the primary vertex We put the severe restriction for the algorithm of SATracking No cluster sharing at B0 Use the primary vertex for the track reconstruction The large DCA can not be measured. We might remove this limitation in p+p 2012/3/8 PHENIX Colaboration FSU.

Acceptance with VTX in DATA
pT distribution Acceptance in data Peripheral events are used in this study. (BbcCharge<100) ~ 60-92% Ratio nhit>=2/N_CNT = 0.6 nhit>=3/N_CNT = 0.35 nhit>=4/N_CNT = 0.1 nhit>=3&chi2<10/N_CNT = 0.2 nhit>=4&chi2<10/N_CNT = 0.06 It seems that the dead area makes acceptance small. In case of ideal geometry, the efficiency with 2hit is 96% 1)CNT 2)CNT + nhit>=2 3)CNT + nhit>=3 4)CNT + nhit>=4 5)CNT + nhit>=3 + chi2<10 6)CNT + nhit>=4 + chi2<10 pT (GeV/c) Acceptance 2012/3/8 PHENIX Colaboration FSU. pT (GeV/c)

Performance of CATracking in the ideal geometry
Acceptance pT[GeV/c] 1)CNT 2)CNT + nhit>=2 3)CNT + nhit>=3 4)CNT + nhit>=4 5)CNT + nhit>=3 + chi2<10 6)CNT + nhit>=4 + chi2<10 Acceptance w.r.t CA Track Simulation Single particle of Pi+ and Pi- 10*10000events 0.5um in X-Y vtx and 1 cm in Z-vtx Flat pT < 4 GeV/c Acceptance nhit>=2/N_CNT = 0.96 nhit>=3/N_CNT = 0.9 nhit>=4/N_CNT = 0.5 nhit>=3&chi2<10/N_CNT = 0.35 nhit>=4&chi2<10/N_CNT = 0.2 Acceptance Curve Acceptance increases gradually with higher pT up to 1GeV/c in pT and is flat for higher pT. The curve is due to the acceptance of the VTX. See active area in the plot. We lose the tracks with lower pT = N_CNT with VTX associated N_CNT Active Area Charge/pT 2012/3/8 PHENIX Colaboration FSU. Phi0

Acceptance in Single particle Sim
Raw pT distribution Simulation Single particle of Pi+ and Pi- 10*10000events 0.5um in X-Y vtx and 1 cm in Z-vtx Flat pT < 4 GeV/c Ratio nhit>=2/N_CNT = 0.96 nhit>=3/N_CNT = 0.9 nhit>=4/N_CNT = 0.5 nhit>=3&chi2<10/N_CNT = 0.35 nhit>=4&chi2<10/N_CNT = 0.2 Turn-ON curve Efficiency increase gradually with higher pT up to 1GeV/c in pT. This is slightly slow. Should be more steep 1)CNT 2)CNT + nhit>=2 3)CNT + nhit>=3 4)CNT + nhit>=4 5)CNT + nhit>=3 + chi2<10 6)CNT + nhit>=4 + chi2<10 pT[GeV/c] Ratio 2012/3/8 pT[GeV/c] PHENIX Colaboration FSU.

Simulation Study 2 Acceptance in phi0
N>=3+B3 N>=3+B2 CNT N>=2 N>=3 N>=4 In the right plot, N+B3 (N+B2) has some spike structures since there are open areas btw ladders in the strip. B3 and B2 has open area independently. By requiring N>=4, the combination of the open area in B2 and B3 decrease the actual active area. 2012/3/8 PHENIX Colaboration FSU.

Simulation Study 3 phi0 phi0 N>=3 N=3&&B3 N>=3 N=3&&B2 20.8% 21.3% phi0 𝑁≥3 Combination of B0, B1, B2 B0, B1, B3 B0, B1, B2, B3 B0, B2, B3 (negligible) B1, B2, B3 (negligible) 1) 1)+2)+3)+4)+5) =20.8% 2) 1)+2)+3)+4)+5) =21.3% 3) 1)+2)+3)+4)+5) =55.5% N>=3 N>=4&&B3&&B2 55.5% Ratio of Active Area 𝑁≥4 𝑁≥3 = 2012/3/8 PHENIX Colaboration FSU.

Track Finding Algorithm
dphi range CNT track Use CNT track as a seed. Assuming track comes from prim vertex. Search the associated hit at the outer layer(cf:B3) with loose dphi cut Track from secondary vtx has lager dphi First hit is not only at B3, but at the other layer. |dphi| < 4mm Search the next associated hit using the hit correlation The difference btw hit at B3 and B2 should be small if these hit are made from a single track. This cut is called as “correlation cut” 2 dimensional cut is applied. |dphi3-dphi2|< 2mm |dz3 –dz3|< 5mm This is too loose. B3 dphi3 Actual Track B2 dphi2 B1 B0 dphi3 vs dz3 dphi3 (cm) dphi3 (cm) dz3 (cm) dphi2 (cm) 2012/3/8 PHENIX Colaboration FSU.

Track Finding Algorithm 2
Determine the best combination of the associated hit with the CNT track Chi-Square 𝜎 𝑝ℎ𝑖 , 𝜎 𝑧 were determined using the data Sigma vs p is fit by the empirical function f(p) = a + b/p^c, a,b,c is parameter Currently dphi is well calibrated, but dZ is on going (close to be done). 𝜎 𝑝ℎ𝑖 is reliable, but 𝜎 𝑧 gives wider than the actual sigma. B3 Actual Track 𝜒 2 = 𝑑𝑝ℎ𝑖′ 𝜎 𝑝ℎ𝑖 𝑑𝑧′ 𝜎 𝑧 2 𝑑𝑝ℎ 𝑖 ′ =𝑑𝑝ℎ 𝑖 𝑖 −𝑑𝑝ℎ 𝑖 𝑗 𝑑 𝑧 ′ =𝑑 𝑧 𝑖 −𝑑 𝑧 𝑗 B2 B1 B0 P dependence of 𝜎 𝑝ℎ𝑖 𝜎 𝑝ℎ𝑖 2012/3/8 PHENIX Colaboration FSU. p(GeV/c)

Offsets of the Coordinate Systems and Beam Center
We have 3 coordinate systems CentArm coordinate (PHENIX coordinate) for the central arm VTX west and east barrel coordinate systems Geometrically independent each other. VTX coordinate should be aligned to the CA coordinate (PHENIX) The beam position can be used as a reference point to adjust these coordinate systems. DCH measures the beam position using the zero field data VTX measures the beam position using the full field data for the west and east separately. East DC Central Arm West BeamCenter 2012/3/8 PHENIX Colaboration FSU.

Offsets of the Coordinate Systems and Beam Center2
Beam center measurement for the offset DCH measures the beam center using the zero field data Alpha angle vs phi in DC VTX measures the beam position using the full field data DCA vs phi in VTX is fit by DCA = Ybeam*cosφb - Xbeam*sinφb Beam center and the offset of the coordinate systems is determined Offset of VtxToCnt = (-0.169,-0.122,0.) (cm) Offset of EastToWest = (0.132,-0.010, ) (cm) Beam center = (0.052, ) (cm) 　α alpha DCA (cm) 2012/3/8 phi Made by Hidemitsu PHENIX Colaboration FSU. Made by Hidemitsu phi

Geometry Alignment in phi 2
We found the problem after the dphi alignment. This work is done by Maya Phi dependence of dphi has a slope We considered this is why the ladders are placed in the shifted radius Track R difference ϕ dϕ Ladder In software In real If the ladder is place at the shifted R, dphi has an additional dϕ This shift can be estimated by fitting the function: 𝒅𝝋=𝑨∙tan 𝝋+𝑩 A: R difference (should be shifted) B: Center position in phi at each ladder. Before After (plot made by MAYA) 2012/3/8 PHENIX Colaboration FSU.

DCA correction by dphi3 DCA0 is calculated using track vector by DCH and hit at B0. The direction of the measured track vector is slightly changed by multiple scattering. Therefore DCA0 is not true DCA. This MS effect must be corrected. Track bending by B-field is also corrected. DCA=DCA0 – a(dp3-DCA0) a is a factor determined by the ratio of the length l3 and l0. Measured vector at DCH DCH B3 True track vector l3 B0 l0 DCA0 2012/3/8 DCA PHENIX Colaboration FSU.

pT dependence of sigma Sigma vs pT Sigma(cm) (cm) (cm) (cm) (cm) (cm) (cm) (cm) (cm) pT(GeV/c) Residual distritubion is Fit by gaussian Sigma vs pT is fit by f(p) = a + b/p^c Currently dphi is considered. for a while, dphi is well aligned. (cm) (cm) 2012/3/8 PHENIX Colaboration FSU.

Chi2 distribution for Nhit (homework)
Nhit is equivalent with N-1 NDF. Nhit=2 Nhit=3 Nhit>3 𝜒 2 = 𝑑𝑝ℎ𝑖 𝜎 𝑝ℎ𝑖 𝑑𝑧 𝜎 𝑧 2 dphi, dz is difference btw dphi_N – dphi_M (N,M is sublayer ID =0 ~ 7) 2012/2/16 RIKEN VTX software meeting

DCA distribution with chi2(dphi) cut
Selection: |dphi3|<0.5, |dz3|<0.5, chi2 (dphi) cut, pT>1GeV/c The tail reduces significantly with tighter chi2(dphi) cut 2012/3/8 PHENIX Colaboration FSU.

Fast DST production in Run 12
y-vtx(cm) x-vtx(cm) DCA(pT>1GeV/c) The fast production is in progress /common/s15/phnxreco We can use the DST for quick QA and analysis. We must repeat geometry alignment. Gaussian sigma is 110um (cm) 2012/3/8 PHENIX Colaboration FSU.

From Run 12 Result from fast production Run dependence of the beam position in X-Y Beam profile and beam center is changing with run number. Y-beam (cm) X-beam (cm) 2012/3/8 PHENIX Colaboration FSU.

Active Area in Run 11 and 12 Run 11 Run 12 2012/3/8 PHENIX Colaboration FSU.

Run 11 Run 12 2012/3/8 PHENIX Colaboration FSU.

Remaining Items of the code development on Central Arm based tracking
Speed up the reconstruction. Algorithm check by simulation. Photon Conversion Tagging … 2012/3/8 PHENIX Colaboration FSU.

Z vertex Sigma = 56. 2012/3/8 PHENIX Colaboration FSU.

<cos2(s-n)> <sin2(s-n)> Trk (pT>0.5) s-n Trk wgt=1 s-n Trk wgt=1 (pT>0.5) s-n L0 s-n L1 s-n L2 s-n L3 s-n Cls s-n Trk s-n 0.4 0.2 0.0 -0.2 |Dh|>0.0 0.4 0.2 0.0 -0.2 pT weighting does not improve the resolution… |Dh|>0. 0.4 0.2 0.0 -0.2 |Dh|>0 rxn s-n ~ 0.35 centrality by bbc charge sum (0~100%) 2012/3/8 PHENIX Colaboration FSU.

VTX Cluster R.P. correlation with BBC/MPC R.P.
<cos n(n)> <sin n(n)> VTX Cluster R.P. correlation with BBC/MPC R.P. BBC s-n MPC s-n VTX Cluster R.P BBC BBCs BBCn MPC MPCs MPCn 0.4 0.2 0.0 -0.2 n=2 0.4 0.2 0.0 -0.2 n=3 centrality by bbc charge sum (0~100%) 0.25/0.41 ~ 0.61 0.31/0.52 ~ 0.60 2012/3/8 PHENIX Colaboration FSU.

zoom - in <cos n(n)> <sin n(n)>
VTX Cluster R.P. correlation with BBC/MPC R.P. BBC s-n MPC s-n VTX Cluster R.P BBC BBCs BBCn MPC MPCs MPCn 0.4 0.2 0.0 -0.2 n=2 0.4 0.2 0.0 -0.2 0.1 0.0 -0.1 zoom - in n=3 centrality by bbc charge sum (0~100%) 2012/3/8 PHENIX Colaboration FSU.

Reaction Plane Measurement
RP VTX cluster West RP VTX Cluster East RP VTX cluster RP BBC 2012/3/8 PHENIX Colaboration FSU.

Residual Distributions
Assosiation is working. dphi3 width is a few mm. Diff btw dphi3-dphi2 is narrow with few 100um (|dphi3|<0.5&& |dz|<0.5) dphi0 width is a few 100um. dphi, dz<0.5 |dp3-dp2|<0.05 dphi at B3 dphi vs dz at B3 cm dz (cm) dphi (cm) dphi3 – dphi2 dphi3 vs dphi2 cm dphi2 (cm) dphi3 (cm) dphi0 dphi0 vs dz0 cm dz (cm) dphi (cm) 2012/3/8 PHENIX Colaboration FSU.

DCA distribution DCA vs c/pT DCA vs dphi0 Run349679 One segment is analyzed. There is no strange correlation with 1/pt and phi0 There is a small alignment issue at East side DCA width is 180um This is due to the calculation. No MS effect is taken into account. Need to update. 2012/3/8 PHENIX Colaboration FSU.

Alignment of the coordinate system between DCH and VTX
We have 3 coordinate systems DCH coordinate (PHENIX coordinate) for the central arm VTX west and east barrel coordinate systems Geometrically independent each other. VTX coordinate should be aligned to the DCH coordinate (PHENIX) The beam position can be used to adjust these coordinate systems. DCH measures the beam position using the zero field data Alpha angle vs phi in DC VTX measures the beam position using the both zero and full field data DCA vs phi in VTX If the beam center is shifted w.r.t the origin of the coordinate. These distribution has a tangent like curve. Hidemitsu is working to determine the beam center for both DCH and VTX 2012/3/8 PHENIX Colaboration FSU.

Coordinate Systems East DC Central Arm West Beam center measured by these coordinate system BeamCenter 𝑉 𝑏𝑒𝑎𝑚 𝐷𝐶𝐻 : Beam center on the DCH 𝑉 𝑏𝑒𝑎𝑚 𝑊𝑒𝑠𝑡 : Beam center on the VTX west 𝑉 𝑏𝑒𝑎𝑚 𝐸𝑎𝑠𝑡 : Beam center on the VTX east 𝑑𝑉 𝑊𝑒𝑠𝑡−𝐷𝐶𝐻 : difference btw DCH and VTX west 𝑑𝑉 𝐸𝑎𝑠𝑡−𝑊𝑒𝑠𝑡 : difference btw VTX east and VTX west 𝑑𝑉 𝑊𝑒𝑠𝑡−𝐷𝐶𝐻 and 𝑑𝑉 𝐸𝑎𝑠𝑡−𝑊𝑒𝑠𝑡 are the offset 2012/3/8 PHENIX Colaboration FSU.

DCH – beam center alignment
alpha Beam center phi BeamCenter_X(west): cm BeamCenter_Y(west): cm Plot α　vs　φ Fit by the function 　α Where R= 2.24m (reference radius) (dx,dy) : beam offset 2012/3/8 PHENIX Colaboration FSU. ref : AN923

Calculation of the beam center using the VTX
Y Beam center (xoffset,yoffset) (x0,y0) hit at L0 (pixel) (x1,y1) hit at L1 (pixel) L0 L1 DCA from (0,0) vtxy: intersection point at x=0) φb:angle of track in XY -plane φb=atan 𝑦1−𝑦0 𝑥1−𝑥0 DCA = BeamY*cosφb - BeamX*sinφb fit function DCA b (This is calculated in VTX internal coordinate) 2012/3/8 PHENIX Colaboration FSU.

Estimation of Background For DCA Distribution DC tracks were rotated plus minus 5 degrees in theta and phi direction randomly. SVX track is associated with rotated DC track. The width of search window for svx cluster on each layer is within plus minus 4mm. At least, 2 clusters are needed for track association. If DC track rotated 5 degrees, shifted distance on B1 is 5mm. pm 5 deg Central track SVX hit cluster 5mm Outer most pixel layer 5 cm 2012/3/8 PHENIX Colaboration FSU.

Residual Distribution on B1, B2 and B3 w and w/o Rotation Blue : |Tilt angle of DC| = 0 degree Red : |Tilt angle of DC| = 5 degree Barrel Barrel 1 Barrel Barrel3 [ cm ] [ cm ] [ cm ] [ cm ] Barrel Barrel 1 Barrel Barrel3 [ cm ] [ cm ] [ cm ] [ cm ] Cut condition Residual on barrel 3 < 0.5 cm Four layer hit pT > 1 GeV/c 2012/3/8 PHENIX Colaboration FSU.

DCA Distribution Blue : |Tilt angle of DC| = 0 degree Red : |Tilt angle of DC| = 5 degree 2012/3/8 PHENIX Colaboration FSU. [ cm ]

RIKEN VTX software meeting
DCA correction by dphi3 DCA0 is calculated using track vector by DCH and hit at B0. The direction of the measured track vector is slightly changed by multiple scattering. Therefore DCA0 is not true DCA. This MS effect must be corrected. Track bending by B-field is also corrected. DCA=DCA0 – a(dp3-DCA0) a is a factor determined by the ratio of the length l3 and l0. Measured vector at DCH DCH B3 True track vector l3 B0 l0 DCA0 2012/1/26 DCA RIKEN VTX software meeting

RIKEN VTX software meeting
DCA correction 2 The factor a = 0.20 After applying the correction, the DCA width is 81um (obtained by gaussian fitting) DCA is measured with pT>1GeV/c DCA0(cm) DCA(cm) dphi3 – DCA0(cm) dphi3 – DCA0(cm) DCA(cm) 2012/1/26 RIKEN VTX software meeting

Current Status of the VTX analysis and the DCA measurement

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Current Status of the VTX analysis and the DCA measurement

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