CASTOR Detector Study.

• re-processed files

Motivation

• Flow effect could be detected in high eta regin, eta < -5 at CASTOR detector.
• Run Number : 151027
• Centrality Cut : 0 ~ 60%

CASTOR detector performance.

• From 17 November 2010 CMS General Weekly Meeting, CERN, "Status and prospects of the CASTOR calorimeter", page 7.
  • Mod. 7 and Mod. 8 had been broken by the magnetic field.
• For aquiring a flow signal, the sectors were merged along the module.

Energy and Hit Distribution.

• The hit distribution was filled same value, 65649, but the energy distribution was not symmetry.
• A number flow, dN/d(phi-psi2) could not be counted, then a new hit definition was needed.

Castor Hit Distribution Module by Sector	Castor Energy Distribution Module by Sector

Merged Module.

• As you can see the Merged each module plots, a number of 60 GeV hit energy was regarded background.
• Then, the hit definition is determined to cut 0 ~ 60 GeV.

	Sector 1	Sector 2	Sector 3	Sector 4
Merged each module

	Sector 5	Sector 6	Sector 7	Sector 8
Merged each module

	Sector 9	Sector 10	Sector 11	Sector 12
Merged each module

	Sector 13	Sector 14	Sector 15	Sector 16
Merged each module

Track Event Plane.

A Blue line is number of track by track phi without detector weighting. After weighting, dN/Phi distributions are flating.	As you can see the blue line, dN/dPsi was tilted to 90 degree. After weighting, the red line has still little fluctuation but not tillted.

Elliptic Flow in CASTOR except Mod.6, Mod.7, Mod.8 and Mod.9.

• From 2D module-sector energy distribution, the module 6 to 9 energy distribution was not symmetry because magnetic effect.
• The Mod.10-Sec.5, Mod.12-Sec.7 and Mod.13-Sec.13 are much lower than other sectors in each module.
• That parts are corrected to multiply by 10/9 ratio.

Little fluctuation but not tilted. Almost hits are symmetric over phi.	It shows that energy distiribution over phi is symmetric with new hit definition, 0~60 GeV

dN/d(phi-psi) looks flat but has cosine fluctuation.	As looking 0 and Pi, a TRACKER and CASTOR are showing similar event plane in energy scale.

Measured v2 without track correction. It shows oppositing ordinary flow shape.	The v2 value is too high. It needs correction.

Corrected v2

• Track v2 resolution
• Seperated two part in eta regin, -2.0 ~ 2.0, to -2.0 ~ -0.4 and 0.4 ~ 2.0.

dN/dPhi track weighting in eta regin -2.0<eta<-0.4.	This plot is TRACKER minus eta regin track dN/d(phi-psi)

dN/dPhi track weighting in eta regin 0.4<eta<2.0.	This plot is TRACKER plus eta regin track dN/d(phi-psi).

v2 resolution

Summary