NA62 Collaboration Meeting – Anacapri 1 September 2009 Massimiliano Fiorini CERN

Data samples and reconstruction NA62 Monte Carlo only Gigatracker enabled: all other detectors excluded 2 data samples: Multiple Coulomb Scattering (MSC) switched ON MSC switched OFF ~200 M events generated for each sample Reconstruction for the Gigatracker hit information  pixels  clusters from cluster position extract kaon kinematic variables (p K, θ X and θ Y ) overlay implemented in MC but still needs some check: for the moment just single track in “trigger” time window

New classes added (1) class GigaTrackerPixel gathers all the hits’ energy belonging to the same pixel sensitive volume methods implemented: AddEnergy(Double_t) GetNHit() GetEnergy() SetTime(Double_t) GetTime() GetPixelID() GetPositionX() GetPositionY() SetClusterID(Int_t) GetClusterID()

New classes added (2) class GigaTrackerCluster collection of adjacent pixels (side-side, corner-corner) in a C++ vector methods implemented: AddPixel(GigaTrackerPixel) GetNPixels() GetPixelVector() GetDistance(GigaTrackerCluster) GetEnergy() GetTime() GetPositionX() GetPositionY() GetWPositionX() GetWPositionY()

Beam Spectrometer Layout pπpπ pKpK pυpυ pυpυ θ πK 13.2 m9.6 m 60 mm GTK2 GTK3 GTK1 2 nd achromat 3 GigaTracKer (GTK) stations 4 bending magnets (vertical view – above picture) plus 1 trim magnet (horizontal view) GTK geometry, materials, pixel structure and magnets implemented in Monte Carlo by Simone B. (see his presentation on April 1 st 2009, Physics Sensitivity WG)

Single Gigatracker Station 60 mm × 27 mm station dimensions 300  m × 300  m pixel cells 18 k pixels per station GTK station materials and thickness: Si sensor (200  m thickness) Sn-Pb bump bonds (15  m thickness, 10  m diameter cylinder) Si read-out chip (100  m thickness) carbon fiber support (100  m thickness) foreseen modifications: add rectangular 300  m × 400  m pixels (according to final sensor design) include geometry and materials of cooling system(s)

Beam line geometry

Vertical view (1) Δ 12 = 13.2 m 60 mm GTK2 GTK3GTK1 Δ 23 = 9.6 m Δ 13 = 22.8 m Δ bend = 3.6 m θYθY (BL) bend = Tm

Vertical view (2)

Error estimate ( θ Y ) ~5.4  rad ~13  rad~7.5  rad total contribution ~16.0  rad

Error estimate (p K ) 0.06%0.08%0.15% 0.12% total contribution ~0.22%

Horizontal view (1) Δ 12 = 13.2 m GTK2GTK3GTK1 Δ 23 = 9.6 m Δ 13 = 22.8 m Δ trim = 625 mm θXθX (BL) trim = Tm

Horizontal view

Error estimate ( θ X ) ~5.4  rad~2.6  rad ~13  rad~7.5  rad total contribution ~16.2  rad

Reconstructed kinematic variables

Kaon momentum (p K ) mean: 75 GeV/c r.m.s.: GeV/c tails (mean ± 3 r.m.s.) amount to ~1.3 × of total

Kaon horizontal ( θ X ) angle mean: -1.2 mrad r.m.s.: ~92  rad

Kaon horizontal ( θ Y ) angle mean: 0 mrad r.m.s.: ~98  rad

Resolutions

Resolution on p K r.m.s.: GeV/c (δp/p ~ 0.21 %)

Resolution on θ X r.m.s.: 16.3  rad sigma (gaussian fit): ~12  rad

Resolution on θ Y r.m.s.: 15.9  rad sigma (gaussian fit): ~12  rad

Multiple Scattering (MSC) switched off

Resolution on p K (1) r.m.s.: GeV/c (δp/p ~ 0.19 %)

Resolution on p K (2)

Resolution on θ X (1) r.m.s.: 11.6  rad

Resolution on θ X (2)

Resolution on θ Y (1) r.m.s.: 11.1  rad

Resolution on θ Y (2)

Cutting on reconstructed momentum

Kaon momentum (p K ) mean: 75 GeV/c r.m.s.: GeV/c cut distribution tails (mean ± 3 r.m.s.) reject ~1.3 × of events

Resolution on p K (1) r.m.s.: GeV/c (δp/p ~ 0.20 %)

Resolution on p K (2) r.m.s.: GeV/c (δp/p ~ 0.20 %)

Resolution on θ X r.m.s.: 15.9  rad

Resolution on θ Y r.m.s.: 15.5  rad

Conclusions and To Do List GTK (single) track reconstruction implemented resolutions as expected: δp K /p K ~ 0.21 % (r.m.s.) δθ X ~ δθ X ~16  rad (r.m.s.) complete reconstruction will be included when MC track overlay will be checked To Do list careful study of distribution tails include track quality parameter study correlations between variables use different PhysicsList simulate (and parametrize) charge sharing in nearby pixels update GTK MC description according to latest modifications

SPARES

Cutting on reconstructed p K, θ X and θ Y

Kaon momentum (p K ) cut distribution tails (mean ± 3 r.m.s.) for the three distributions reject 2.0 × of events

Kaon angles ( θ X and θ Y )

Resolution on p K r.m.s.: GeV/c (δp/p ~ 0.20 %)

Resolution on θ X r.m.s.: 15.7  rad

Resolution on θ Y r.m.s.: 15.5  rad