Modification of the near-side jet peak at √ s NN = 2 . 76 TeV Pb–Pb collisions measured by the ALICE detector Mónika Kőfaragó CERN ALICE, Utrecht University 6th May 2016 Wigner Theoretical Physics Seminar
The current ALICE detector Strip (SSD) Current ITS Drift (SDD) Pixel (SPD) Current ITS has six layers Only two layers equipped with pixel detectors Mónika Kőfaragó Modification of the near-side jet peak 2 / 11
Upgrade of ALICE in the 2nd LHC long shutdown (2019/2020) Motivations and strategy: High precision measurements of heavy flavor and charmonia at low p T and low-mass dileptons cannot be selected by a hardware trigger Record large minimum bias samples read out all Pb–Pb collisions at 50 kHz Integrated luminosity of 10 nb − 1 in Pb–Pb (plus pp and p–A data) factor 100 in statistics compared to LHC Run 1 and 2 (2009 - 2019) Mónika Kőfaragó Modification of the near-side jet peak 3 / 11
Upgrade of ALICE in the 2nd LHC long shutdown (2019/2020) Motivations and strategy: High precision measurements of heavy flavor and charmonia at low p T and low-mass dileptons cannot be selected by a hardware trigger Record large minimum bias samples read out all Pb–Pb collisions at 50 kHz Integrated luminosity of 10 nb − 1 in Pb–Pb (plus pp and p–A data) factor 100 in statistics compared to LHC Run 1 and 2 (2009 - 2019) Upgrades: Electronics and readout of the New Inner Tracking System (ITS) Time-Projection Chamber (TPC) New Muon Forward Tracker (MFT) Readout electronics of several Smaller beam pipe detectors Online and offline system New Fast Interaction Trigger (FIT) Mónika Kőfaragó Modification of the near-side jet peak 3 / 11
Design objectives for the upgrade of the ITS Improve impact parameter resolution by a factor of 3 ( 5 ) in r- ϕ (z) at p T = 500 MeV / c First layer closer to interaction point: 39 mm → 23 mm Material budget: ∼ 1 . 14 % X 0 → 0 . 3 % X 0 for the three innermost layers Pixel size: 50 µ m × 425 µ m → 29 µ m × 27 µ m CERN-LHCC-2013-24 J. Phys. G(41) 087002 Mónika Kőfaragó Modification of the near-side jet peak 4 / 11
Design objectives for the upgrade of the ITS Improve impact parameter resolution by a factor of 3 ( 5 ) in r- ϕ (z) at p T = 500 MeV / c First layer closer to interaction point: 39 mm → 23 mm Material budget: ∼ 1 . 14 % X 0 → 0 . 3 % X 0 for the three innermost layers Pixel size: 50 µ m × 425 µ m → 29 µ m × 27 µ m Improve tracking efficiency and p T resolution at low p T 6 layers → 7 layers All layers pixel chips (instead of strip, drift and pixel layers) CERN-LHCC-2013-24 J. Phys. G(41) 087002 Mónika Kőfaragó Modification of the near-side jet peak 4 / 11
Design objectives for the upgrade of the ITS Improve impact parameter resolution by a factor of 3 ( 5 ) in r- ϕ (z) at p T = 500 MeV / c First layer closer to interaction point: 39 mm → 23 mm Material budget: ∼ 1 . 14 % X 0 → 0 . 3 % X 0 for the three innermost layers Pixel size: 50 µ m × 425 µ m → 29 µ m × 27 µ m Improve tracking efficiency and p T resolution at low p T 6 layers → 7 layers All layers pixel chips (instead of strip, drift and pixel layers) Fast readout (present ITS is limited to 1 kHz) Pb-Pb: up to 100 kHz pp: several 100 kHz Fast insertion/removal for yearly maintenance CERN-LHCC-2013-24 J. Phys. G(41) 087002 Mónika Kőfaragó Modification of the near-side jet peak 4 / 11
Requirements for the upgrade of the ITS Outer layers Middle layers 7 layers of pixel sensors ( r = 23 − 400 mm) Inner layers 10 m 2 of silicon with 12 . 5 Gpixels | η | < 1 . 22 for tracks from 90 % of Beam pipe the most luminous region Mónika Kőfaragó Modification of the near-side jet peak 5 / 11
Requirements for the upgrade of the ITS Outer layers Middle layers 7 layers of pixel sensors ( r = 23 − 400 mm) Inner layers 10 m 2 of silicon with 12 . 5 Gpixels | η | < 1 . 22 for tracks from 90 % of Beam pipe the most luminous region Parameter Inner barrel Outer barrel Silicon thickness 50 µ m 100 µ m Spatial resolution 5 µ m 10 µ m < 300 mW / cm 2 < 100 mW / cm 2 Power density Event resolution < 30 µ s Detection efficiency > 99 % < 10 − 6 per event per pixel Fake hit rate 15 - 35 cm − 2 0 . 1 - 1 cm − 2 Average track density TID radiation * 2700 krad 100 krad 1 . 7 × 10 13 1 MeV n eq /cm 2 10 12 1 MeV n eq /cm 2 NIEL radiation * * Including a safety factor of 10 Mónika Kőfaragó Modification of the near-side jet peak 5 / 11
Technology choice M onolithic A ctive P ixel S ensors using TowerJazz 0 . 18 µ m CMOS imaging process High-resistivity ( > 1k Ω cm) epitaxial layer on p-type substrate Quadruple well process: deep PWELL shields NWELL of PMOS transistors, allowing for full CMOS circuitry within active area Moderate reverse substrate biasing is possible, resulting in larger depletion volume around NWELL collection diode NWELL NMOS PMOS DIODE TRANSISTOR TRANSISTOR PWELL PWELL NWELL DEEP PWELL h Drift e e h Diffusion h e e h Epitaxial Layer P- Substrate P++ Mónika Kőfaragó Modification of the near-side jet peak 6 / 11
Specification of the pALPIDE-1 First prototype with final size (15 mm × 30 mm) 15 mm 512 × 1024 pixels 0 1 2 3 Pixels are 28 µ m × 28 µ m Digital readout with priority encoder 30 mm Four sectors with different pixel geometries and reset mechanisms Mónika Kőfaragó Modification of the near-side jet peak 7 / 11
Specification of the pALPIDE-1 First prototype with final size (15 mm × 30 mm) 15 mm 512 × 1024 pixels 0 1 2 3 Pixels are 28 µ m × 28 µ m Digital readout with priority encoder 30 mm Four sectors with different pixel geometries and reset mechanisms VPULSE AVDD PMOS Reset Diode Reset C inj 230 aF VRESET VAUX IBIAS ITHR IDB Cs source D0 M0a M0b pix_in M1 VCASN M4 IRESET PIX_OUT_B D1 VCASP M2 AVSS pix_out M5 PWELL curfeed M3 Cf AVSS Mónika Kőfaragó Modification of the near-side jet peak 7 / 11
Specification of the pALPIDE-1 First prototype with final size (15 mm × 30 mm) 15 mm 512 × 1024 pixels 0 1 2 3 Pixels are 28 µ m × 28 µ m Digital readout with priority encoder 30 mm Four sectors with different pixel geometries and reset mechanisms VPULSE AVDD PMOS Reset Diode Reset C inj 230 aF VRESET VAUX IBIAS ITHR IDB Cs source D0 M0a M0b pix_in M1 VCASN M4 IRESET PIX_OUT_B D1 VCASP M2 AVSS pix_out M5 PWELL curfeed M3 Cf AVSS Two types of reset mechanisms Mónika Kőfaragó Modification of the near-side jet peak 7 / 11
Specification of the pALPIDE-1 First prototype with final size (15 mm × 30 mm) 15 mm 512 × 1024 pixels 0 1 2 3 Pixels are 28 µ m × 28 µ m Digital readout with priority encoder 30 mm Four sectors with different pixel geometries and reset mechanisms VPULSE AVDD PMOS Reset Diode Reset C inj 230 aF VRESET VAUX IBIAS ITHR IDB Cs source D0 M0a M0b pix_in M1 VCASN M4 IRESET PIX_OUT_B D1 VCASP M2 AVSS pix_out M5 PWELL curfeed M3 Cf AVSS Input node where charge is collected Mónika Kőfaragó Modification of the near-side jet peak 7 / 11
Specification of the pALPIDE-1 First prototype with final size (15 mm × 30 mm) 15 mm 512 × 1024 pixels 0 1 2 3 Pixels are 28 µ m × 28 µ m Digital readout with priority encoder 30 mm Four sectors with different pixel geometries and reset mechanisms VPULSE AVDD PMOS Reset Diode Reset C inj 230 aF VRESET VAUX IBIAS ITHR IDB Cs source D0 M0a M0b pix_in M1 VCASN M4 IRESET PIX_OUT_B D1 VCASP M2 AVSS pix_out M5 PWELL curfeed M3 Cf AVSS Charge is transfered from C S to the output node Mónika Kőfaragó Modification of the near-side jet peak 7 / 11
Specification of the pALPIDE-1 First prototype with final size (15 mm × 30 mm) 15 mm 512 × 1024 pixels 0 1 2 3 Pixels are 28 µ m × 28 µ m Digital readout with priority encoder 30 mm Four sectors with different pixel geometries and reset mechanisms VPULSE AVDD PMOS Reset Diode Reset C inj 230 aF VRESET VAUX IBIAS ITHR IDB Cs source D0 M0a M0b pix_in M1 VCASN M4 IRESET PIX_OUT_B D1 VCASP M2 AVSS pix_out M5 PWELL curfeed M3 Cf AVSS Pixel is registered as hit Mónika Kőfaragó Modification of the near-side jet peak 7 / 11
Specification of the pALPIDE-1 First prototype with final size (15 mm × 30 mm) 15 mm 512 × 1024 pixels 0 1 2 3 Pixels are 28 µ m × 28 µ m Digital readout with priority encoder 30 mm Four sectors with different pixel geometries and reset mechanisms VPULSE AVDD PMOS Reset Diode Reset C inj 230 aF VRESET VAUX IBIAS ITHR IDB Cs source D0 M0a M0b pix_in M1 VCASN M4 IRESET PIX_OUT_B D1 VCASP M2 AVSS pix_out M5 PWELL curfeed M3 Cf AVSS Two main parameters to change the charge threshold Mónika Kőfaragó Modification of the near-side jet peak 7 / 11
Specification of the pALPIDE-1 First prototype with final size (15 mm × 30 mm) 15 mm 512 × 1024 pixels 0 1 2 3 Pixels are 28 µ m × 28 µ m Digital readout with priority encoder 30 mm Four sectors with different pixel geometries and reset mechanisms VPULSE AVDD PMOS Reset Diode Reset C inj 230 aF VRESET VAUX IBIAS ITHR IDB Cs source D0 M0a M0b pix_in M1 VCASN M4 IRESET PIX_OUT_B D1 VCASP M2 AVSS pix_out M5 PWELL curfeed M3 Cf AVSS Injection capacitance for measuring threshold Mónika Kőfaragó Modification of the near-side jet peak 7 / 11
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