Prospects with the ALICE Inner Tracking System in LS3

d0,⇤b

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pT,⇤b

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✓ : pointing angle

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dca⇤+c ,⇡�

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Dimitra Andreou for the ALICE Collaboration dimitra.andreou@cern.ch

The ALICE experiment is planning the construction of a novel ultra light vertex detector during the next LHC LS3 (2025-2027). The latest innovations in the silicon imaging technology, offer the opportunity to further reduce the thickness and increase the area of the ALPIDE sensors developed for the Inner Tracking System upgrade of LS2. Through the process of stitching, wafer-scale Monolithic Active Pixel Sensors (MAPS) will be produced. These sensors will be thinned down to 20–40µm, a thickness at which the flexibility of silicon allows the bending of the sensor and the construction of cylindrical layers. T h e t h r e e innermost layers of the ITS will be replaced with three layers of curved silicon-only sensors. These novel modifications will reduce the material budget from 0.35% X0 to 0.05% X0 per layer.

The beam pipe will be replaced with a smaller one with Inner Radius (IR) 16mm and thickness 500µm. The reduction of the radial distance of the first layer to the interaction point from 23mm to 18mm along with all t h e above modifications will

i m p r o v e t h e p o i n t i n g

resolution a n d t h e

tracking efficiency of low-momentum particles.

The physics program of the ALICE experiment will benefit from the ITS upgrade mostly for the low pT measurements of c h a r m a n d b e a u t y hadrons and of low-mass dielectrons.

Λ0b

sNN = 5.5TeV

Λb /B

Λ0b → Λ+

c π− , Λ+c → pK−π+

• Thermalisation and hadronization of heavy quarks in medium, in the beauty sector:

• Decay length: 417 µm • Decay channel considered: • Combined B.R.= 0.49% x 6.28% • MC full simulation and reconstruction of

ITS2, 106 Pb—Pb events at • Hijing background + Injected signal

Letter of Intent for an ALICE ITS Upgrade in LS3

• Selection with particle identification and topological cuts

• Multiple rotation method (pion track) for increased background statistics

2 4 6 8 10 12 14 16)c(GeV/

bΛT, p

0

5

10

15

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25

30

35

Sig

nific

ance

ALICE Simulation = 5.5 TeVNNsPb-Pb, , 0-20%-1 = 10 nbintL

) +π-pK→+

cΛ (-π+cΛ→bΛ

UpgradeITS3

ITS2

ALI−SIMUL−332192

Significance measurement

Beampipe inner/outer radius (mm) 16.0/16.5

IB Layer parameters Layer 0 Layer 1 Layer 2

Radial position (mm) 18.0 24.0 30.0Length (sensitive area) (mm) 270 270 270Pseudo-rapidity coveragea ± 2.5 ± 2.3 ± 2.0Pixel sensor dimensions (mm2) 280 ⇥ 56.5 280 ⇥ 75.5 280 ⇥ 94.0Number of pixel sensors/layer 2Pixel size (µm2) O(15 ⇥ 15)b

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ALICE-PUBLIC-2018-013

0 2 4 6 8 10 12 14 163−10×

(cm)cΛ vertex σ

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160

Entri

es/b

in

246810121416182022

610×

ALICE Simulation = 5.5 TeVNNsPb-Pb, , 0-20%-1 = 10 nbintL

c < 9 GeV/T

p ≤6

Upgrade ITS2Signal

Background

0 2 4 6 8 10 12 14 163−10×

(cm)cΛ vertex σ

0

20

40

60

80

100

120

140

160

Entri

es/b

in

1

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3

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5

6

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8

9610×

ALICE Simulation = 5.5 TeVNNsPb-Pb, , 0-20%-1 = 10 nbintL

c < 9 GeV/T

p ≤6

Upgrade ITS3Signal

Background

Signi f icance =Signal

Signal + B(3σ)

• Significance calculation for ITS2 vs ITS3

• Central events 0-20% for luminosity Lint = 10nb−1

Beauty measurements with the new ITS