Performance Study of Pair-monitor 2009/06/30 Yutaro Sato Tohoku Univ.

Pair-monitor 1 Pair-monitor is a silicon pixel detector to measure the beam profile at IP. The distribution of the pair B.G. is used. –The same charges with respect to the oncoming beam are scattered with large angle. –The scattered particles have information on beam shape. The pair-monitor is required to measure the beam size with 10% accuracy. e-e- e+e+ IP e + beam e - beam Pair-monitor Distribution of pair B.G. X [cm] Y [cm] X [cm] 1σ x (nominal)2 σ x

Tohoku group has developed –development of the readout ASIC for the pair-monitor. –the performance study of pair-monitor. The combined analysis with BeamCal was performed. –Pair-monitor is a silicon pixel detector to measure hit counts. –BeamCal is a calorimeter to measure energy deposit. Beam parameters (σ x, σ y, Δ y /σ y ) were reconstructed using the matrix method (second order).Content 2 Offset Δ y [nm] e - bunch e + bunch

Simulation setup CM energy : 500GeV Noinal beam size (σ x 0, σ y 0, σ z 0, ) = ( 639nm, 5.7nm, 300 μm ) Tools : CAIN (Pair background generator) Jupiter (Tracking emulator) Magnetic field : 3.5 T + anti-DID Pair-monitor is located in front of the BeamCal. Scattered e + was studied. 3 LumiCal BeamCal Pair-monitor IP

The beam parameters are reconstructed by the Taylor expansion. → The measurement variables were studied. Matrix method for reconstruction 4 Matrix of the first order termMatrix of the second order term Measurement variable Beam parameter (X) The beam parameters are reconstructed by the inverse matrix.

The radial distribution changes, due to the difference of P t ’ kick at IP. ( P t ’ is the perpendicular momentum to the e - beam line. ) Measurement variables were defined. R max : Radius to contain 97.5% of the all hits. ( Pair-monitor ) R ave : Average radius weighted energy deposit. ( BeamCal ) Radial distribution 5 σ x = 639 [nm] σ x = [nm] Pt’ [MeV] ( R i is the radius of the i-th cell ) e - bunchz’ axis Pt’Pt’ e + bunch e+e+

R max and R ave were obtained with various beam parameters. R max and R ave decrease for larger horizontal beam size (σ x ). Variable : R max and R ave 6 σ y = 5.7 [nm] σ y = 8.55 [nm] σ y = 11.4 [nm] σ y = 17.1 [nm] R max [cm] v.s. Horizontal beam size (σ x ) [nm] R ave [cm] v.s. Horizontal beam size (σ x ) [nm] R max [cm] R ave [cm] Horizontal beam size (σ x ) [nm]

The azimuthal distribution at IP also changes with the beam parameters. The measurement variables with the pair-monitor were defined. → N D1 /N all for vertical beam size (σ y ) N U /N D2 for relative offset (Δ y /σ y ) e - bunch (z’ axis) e + bunch e+e+ e+e+ Azimuthal distribution 7 σ y = 5.7 [nm] σ y = 17.1 [nm] φ’ [rad] Hit distribution

N D1 /N all and N U /N D2 were obtained with various beam parameters. N D1 /N all and N U /N D2 change as a function of the beam parameters. Variable : N D1 /N all, N U /N D2 8 N U /N D2 v.s. Vertical beam size (σ y ) [nm] N U /N D2 N D1 /N all v.s. Vertical beam size (σ y ) [nm] N D1 /N all σ x = 639 [nm] σ x = [nm] σ x = [nm] σ x = [nm] Δ y / σ y = 0 Δ y / σ y = 0.2 Δ y / σ y = 0.4

The total number of hits (N all ) and total energy deposit (Edep all ) also have information of the beam parameters. 1/N all and 1/Edep all change as a function of the σ x and σ y. Variable : 1/N all, 1/Edep all 9 σ x = 639 [nm] σ x = [nm] σ x = [nm] σ x = [nm] Δ y / σ y = 0 Δ y / σ y = 0.2 Δ y / σ y = 0.4 1/N all v.s.Vertical beam size (σ y ) [nm] Vertical beam size (σ y ) [nm] 1/N all

Measurement variables Pair-monitor … R max, N D1 / N all, N U / N D2, 1 / N all BeamCal … R ave, N D / N all, N U / N D, 1 / Edep all Matrix components were determined by the fitting with the second polynomials. Reconstruction of beam size 10 Matrix of the first order term Matrix of the second order term Measurement variable Beam parameter (X) Beam parameter can be reconstructed.

Results (σ y ) Beam sizes were reconstructed using the matrix. The combined analysis provides more precise measurement. 11 Accuracy [%] Vertical beam size (σy) [nm] Pair-monitor BeamCal Pair-monitor + BeamCal Accuracy [%] [ σ x ] 639 [nm] [nm] [nm] [nm] [nm] [nm] [ Δ y /σ y ] ● 0 ■ 0.1 ▲ 0.25 ▼ 0.3 ○ 0.4 Vertical beam size (σy) [nm] Measurement of σ y

Results (σ x, σ y, Δ y /σ y ) The accuracy of measurements is as follows. 12 Pair-monitorBeamCalPair-monitor + BeamCal σxσx 3.2 %4.1 %2.8 % σyσy 10.1%15.6 %8.6 % Δ y /σ y 8.6 %9.4 %7.4 %

Summary Pair-monitor and BeamCal measures the beam profile at IP. –Pair-monitor is a silicon pixel detector to measure the hit count. –BeamCal is a calorimeter to measure the energy deposit. The combined analysis with BeamCal was performed. Beam parameters (σ x, σ y, Δ y /σ y ) are reconstructed using the matrix method (second order). The combined analysis can provide more precise measurement. 13 Pair-monitorBeamCalPair-monitor + BeamCal σxσx 3.2 %4.1 %2.8 % σyσy 10.1%15.6 %8.6 % Δ y /σ y 8.6 %9.4 %7.4 %

Backup 14

Inverse matrix of a non-square matrix A is defined as follows. Matrix method for reconstruction 15 Matrix of the first order term Measurement variable Beam parameter (X)

R max and R ave 16 Δ y / σ y = 0 Δ y / σ y = 0.2 Δ y / σ y = 0.4 R max [cm] v.s. Horizontal beam size (σ x ) [nm] R ave [cm] v.s. Horizontal beam size (σ x ) [nm] R max [cm] R ave [cm] Horizontal beam size (σ x ) [nm] ( R i is the radius of the i-th cell )

Azimuthal distribution 17 Δ y / σ y = 0 Δ y / σ y = 1.0 φ’ [rad] The measurement variable was defined. → N U /N D2 e - bunch (z’ axis) e + bunch e+e+ e+e+

Variable : N D1 /N all, N U /N D2 18 Δ y / σ y = 0 Δ y / σ y = 0.2 Δ y / σ y = 0.4 N U /N D2 v.s. Vertical beam size (σ y ) [nm] N D1 /N all v.s. Vertical beam size (σ y ) [nm] N D1 /N all N U /N D2 Vertical beam size (σ y ) [nm] σ x = 639 [nm] σ x = [nm] σ x = [nm] σ x = [nm]

Variable : 1/N all, 1/Edep all 19 Δ y / σ y = 0 Δ y / σ y = 0.2 Δ y / σ y = 0.4 σ x = 639 [nm] σ x = [nm] σ x = [nm] σ x = [nm] Vertical beam size (σ y ) [nm] 1/Edep all v.s. Vertical beam size (σ y ) [nm]

Result (σ x ) 20 BeamCal Pair-monitor + BeamCal [ σ x ] 639 [nm] [nm] [nm] [nm] [nm] [nm] [ Δ y /σ y ] ● 0 ■ 0.1 ▲ 0.25 ▼ 0.3 ○ 0.4

Result (Δ y /σ y ) 21 BeamCal Pair-monitor + BeamCal [ σ x ] 639 [nm] [nm] [nm] [nm] [nm] [nm] [ Δ y /σ y ] ● 0 ■ 0.1 ▲ 0.25 ▼ 0.3 ○ 0.4