Internal alignment East barrel West barrel y x

Internal alignment の パラメーターたち East barrel West barrel y x 各sensor (x, y, z) : translation vector 3× 3 : rotation matrix が各々定義されている。　 y O(east) O(west) x Pixel sensor: 30(ladder) × 4(sensor/ladder) = 120 Strip sensor: 16(ladder) × 5(sensor/ladder) +24(ladder)× 6(sensor/ladder) = 224 O(East) to O(West) offset 　 2

　momentum dependence of DCA Simulation High Momentumの粒子ほど、 DCA resolutionがよくなるはず。。。。 - この手法だけではpixelをalignできない（後述） -Stripixelのアラインメント（運動量、magnetic bendの 補正) um Measurement ? ? ? 7

External alignment DCH External alignment of the VTX w. r. t. the DCH is performed using DCH based tracking. Residual = (DCH projection – VTX cluster) Pixel , strip 全ラダーに適用. VTX clusters Residual mean (cm) Ladder# 下村さんのplotより Beam center 9

座標系問題 DCH VTX cluster & Beam center: VTX座標系で計算 DCH Hit (φ, Z) : DCH座標系で計算 両座標系の原点がずれてると、 Residual = (DCH projection – VTX cluster) の計算が狂ってしまう。 Beam center 10

Zero field run を用いてのVTX-DCH座標系合わせ RUN 11 Au+Au 200 Ge. V run after VTX 4 th repair Jun 1 st Jun 2 nd Jun 3 rd Jun 4 th Jun 6 th Jun 7 th Jun 15 th Jun 16 th Jun 20 th VTX Long Access , Magnet Polarity switch Zero filed run 346977 DC made an access Zero filed run 347148, 347149 DC made an access Zero filed run 347796, 347797 access (DC, TOF, RPC, Mu. Trig, Mu. ID) Zero filed run 349005, 349006, 349007 End of 200 Ge. V Au+Au 11

How to calculate the beam center (VTX) Y (x 0, y 0) (x 1, y 1) 1. Accumulate peripheral collision 2. Fit DCA vs φb hit at L 0 (pixel) hit at L 1 (pixel) Beam center (xoffset, yoffset) φb: angle of track in XY -plane 0 X L 0 DCA from (0, 0) L 1 (This is calculated in VTX internal coordinate) fit function DCA = yoffset*cosφb - xoffset*sinφb

DCA west phi DCA Beam center : WEST ( 0. 226 cm, 0. 056 cm) EAST ( 0. 093 cm, 0. 076 cm) phib EAST 13 (phib=atan 2(y, -x) )

Beam offset measured by DCH Thanks to Ciprian and Okada-san 　α R: average radius of the DCH α R= 224 cm (dx, dy) : beam offset >Plot α　vs　φ >Fit with [0]*sin(φ)+[1]*cos(φ) Where [0] = dx/R, [1]= -dy/R for west [0] = dx/R, [1]= dy/R for east ref : AN 923 14

run 346977　result VTX Beam center WEST ( 0. 226 cm, 0. 056 cm) EAST ( 0. 093 cm, 0. 076 cm) DCH Beam center WEST (0. 0484 cm, -0. 0394 cm) EAST (0. 0297 cm, -0. 0362 cm) y y x O(VTX east) O(VTX west) x O(DCH west) x’ = x + d. CNT_VTX + d. EW ： d. CNT_VTX : The offset of the origin of the coordinate system btw the Central Arm and VTX ： d. EW : The offset btw West and East VTX. 全cluster positionはDCH west coordinateでDSTに保存することに決定 15

DCH east – west offset ? ΔYoffset （cm ） ΔXoffset (cm) 346977 347148 347797 349006 たとえばaccessでEast Arm を開けて閉めた後、元の位置に戻っているのか？ →　A. 戻ってない(run 8, 9 pp analysisでも同程度の大きさで、戻ってない) Global Tracking (VTX cluster + DCH Tracking)によるtrack運動量, DCAの計算等に問 題が生ずるのでは？(要議論と思う) 16

Alignment for Stripixel ladder Mikhal’s slide dproj Pixel B 1 Pixel B 0 θ Stripixel Should be zero B The particle has a finite momentum, then particle trajectory bends in B-field. • The residual value between the cluster position and the straight line projection is calculated. • If particle has infinite momentum, the residual value should be zero. • The residual distribution shows 2 peaks structure. Peaks are made from positive and negative particles. • The valley position between 2 peaks should be zero if the detector alignment is perfect. --Ladder position の初期値には図面通りの値を使っていたが、その図面が間違ってて R方向に 3 mmもずれていた。ここ二週間そのせいで相当混乱したが、ひとまず収束。 17

今後の予定 DCHトラックを用いたアラインメント west east iteration Beam center からのDCAを用いた Pixel ladderのアラインメント iteration Track Residualを用いた Stripixel のアラインメント 18

backup 20

DCH alpha vs phi WEST fit alpha phi Xoffset: 0. 0484 +- 0. 0056 cm Yoffset: -0. 0394 +- 0. 0030 cm 21

DCH inner alignment problem alpha phi DCH (WEST) inner-alignment has problem. 22