Charming futureof SHINE
Aleksandra Snochfor NA61/SHINE
Goethe University
Tsukuba Workshop
11/12/2017

Outline• Why open charm is important?

• First measurements in NA61/SHINE 2017-2018• Precise open charm studies in 2021-2024

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Why open charm isimportant?

Questions that motivate open charmmeasurements at the CERN SPS:
• What is the mechanism of open charm production?
• How does the onset of deconfinement
impact open charm production?
• How does the formation of quark gluon plasma
impact 𝐽/𝜓 production?

To answer these questions mean number of charm quark pairs, 𝑐 𝑐ҧ ,produced in the full phase space in A+A collisions has to be known.
Up to now corresponding experimental data does not exist.

4Models of open charm production
Predictions for cതc in central Pb+Pb at 158A GeV/c
differ by a factor of about 50.

pQCD
Gavai et al. IJMP A 10 2999.
Braun-Munzinger, J. Stachel,
PL B 490, 196.
HSD
Linnyk, Bratkovskaya, Cassing,
IJMP E17 1367
HRG, Quark Coalesc. Stat.
Gorenstein, Kostyuk, Stoecker,Greiner, PL B 509, 277.
Quark Coalesc. Dyn.
Levai, Biro, Csizmadia, Csorgo,Zimanyi, JP G 27, 703
SMESGazdzicki, Gorenstein, APP B30,2705.

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Charm yield as the signal of deconfinement
𝑻𝒄 ≈ 𝟏𝟓𝟎𝐌𝐞𝐕

𝐜𝐨𝐧𝐟𝐢𝐧𝐞𝐝 𝐦𝐚𝐭𝐭𝐞𝐫𝐝𝐞𝐜𝐨𝐧𝐟𝐢𝐧𝐞𝐝 𝐦𝐚𝐭𝐭𝐞𝐫ഥ mesons → charm quarks
DD2𝑚D = 3.7 GeV → 2𝑚c = 2.6 GeV
𝑔D = 4 → 𝑔c = 12
central Pb+Pb collisions[Kostyuk, Gorenstein, Greiner,
PL B519 207]

QCD-inspired calculations[Poberezhnyuk, Gazdzicki, Gorenstein,ACTA PHYS POL B 9 48(2017)]

Statistical Model of the Early Stage6𝐽/𝜓 production as the signal of deconfinement
Open charm and 𝐽/𝜓 production within Matsui-Satz model

mediumvacuumpp

𝑃 cതc → 𝐽/𝜓 ≡𝑃vacuum cതc → 𝐽/𝜓

>

𝜎𝐽/𝜓
𝐽/𝜓
≡cതc𝜎cതc[Satz, Adv. High Energy Phys. 2013 (2013) 242918][PL B178 416]

𝑃medium cതc → 𝐽/𝜓

Medium reduces probability of 𝐽/𝜓 production
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𝐽/𝜓 production as the signal of deconfinement
Calculation of 𝑃(cതc → 𝐽/𝜓) requires data on:
𝐽/𝜓 – precise data at
SPS by NA38, NA50,
NA60

•𝜎𝐽/𝜓
𝐽/𝜓
≡cതc
𝜎cതccതc – not available up to now,
NA61 has just started
the corresponding measurementscentral Pb+Pb at 150-158A GeV/c

NA50

first indicationof 𝐷0 signal[CERN-SPSC-2017-038]

NA61[NA50, arXiv:hep-ex/0412036v1]•𝑃 cതc → 𝐽/𝜓 ≡8

𝐽/𝜓 production at the CERN SPS[NA50, PL B 477 28–36][NA50, arXiv:hep-ex/0412036v1]

Data on 𝐽/𝜓 production has been normalized by the Drell-Yan yield

Interpreting these results one frequently assumes:𝑐 𝑐ҧ ~ DY
This assumptions may be incorrect due to many effects:
shadowing, parton energy losses, etc.
9First measurementsin NA61/SHINE
2017-2018

Open charm measurement concept

𝐷0 → 𝜋 + + 𝐾 −𝑐𝜏ഥ ≈ 123 μm
BR = 3.89%

Vertex detector is needed to reconstruct primary vertex
and secondary vertexes with high precision.
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NA61/SHINE setup
Small Acceptance
Vertex Detector

12Small Acceptance Vertex Detector
Small Acceptance Vertex Detector
introduced in 2016:• 16 CMOS MIMOSA-26 sensors
located on two horizontallymovable arms
• target holder integrated

Achieved goals:• tracking in the large track multiplicity
environment• precise primary vertex reconstruction• TPC and SAVD track matching• first search for 𝐷0 and 𝐷0 signal

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Acceptance of SAVDAMPT simulation for central Pb+Pb collisions at 150A GeV/c:
SAVD reconstructs 4% out of all 𝐷0 → 𝜋 + + 𝐾 − decays
all generated

reconstructed14

Vertex Detector performance from 2016 data

From the analysis of the recorded data one concludes that:• Cluster position resolution is 𝜎x,y (𝐶𝑙) ≈ 5 μm
• Primary Vertex resolution is:
𝜎x (𝑃𝑉) ≈ 5 μm,
𝜎y (𝑃𝑉) ≈ 1.8 μm,
𝜎z 𝑃𝑉 ≈ 30 μm.
(𝜎x (𝑃𝑉) > 𝜎y (𝑃𝑉) due to 𝐵y > 𝐵x ≈ 0)

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Search for 𝐷 0 and 𝐷 0First indication of 𝐷0 and 𝐷0 peak16

Xe+La 2017 data taking
About 5M events on central Xe+La collisions at 150A GeV/cwere recorded at the beginning of November.

Based on simulations from Pb+Pb and p-QCD inspired system size dependence,
one expects several hundred of 𝐷0 + 𝐷0 meson decays to be reconstructed.
This should allow to obtain the first physics results on open charm production inheavy ion collisions at the CERN SPS.

Xe+La at 150A GeV/c from 201717

Impact of Xe+La data

[NA60, PRL 99, 132302 (2007)]

𝐽/𝜓 production in In+In (𝐴 = 115) collisions at 158A GeV/c
was precisely measured by NA60.

This data together with NA61 results on open charm productionin Xe+La (𝐴 = 129, 𝐴 = 139) collisions at 150A GeV/cwill strongly challenge theoretical models.
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Pilot data on Pb+Pb at 150A GeV/c in 2018
Data taking in 2018 on central Pb+Pb collisions for open charm measurement
recommended by CERN SPSC in October 2017.

Three weeks of data taking:• 10M central collisions recorded• 4000 𝐷0 and 𝐷0 decays is expected to be reconstructed

Pb+Pb at 150A GeV/c from 201619

Precise open charmstudies in 2021-2024

Upgrades of NA61/SHINE setup
Construction of Large Acceptance
Vertex Detector (LAVD)
for 𝐷0 , 𝐷0 decay reconstruction

Replacement of the TPC
read-out electronics
to increase data rate to 1 kHz

New trigger and dataacquisition system
New Time-of-Flightdetectors

Upgrade of Projectile
Spectator Detector

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Large Acceptance Vertex Detector
General requirements:• Precise vertex measurement• Fast detectors with high granularity• The low material budget• Large acceptanceTechnology developed for ALICE ITS:
• CMOS ALPIDE pixel sensors• Carbon fiber support structure• Read-out electronics
6 stations with about 200 sensors

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Beam request for 2021-2024

Year

BeamDuration

Purpose2021 p at 150 GeV/c

4 weeks

detector tests

2022 Pb at 150A GeV/c

2 weeks

charm in central
collisions

40k

2022 Pb at 150A GeV/c

4 weeks

charm in peripheral
collisions

8k

2023 Pb at 150A GeV/c

2 weeks

charm in mid-central
collisions

20k

2024 Pb at 40A GeV/c

4 weeks

charm in central
collisions

2k

𝑫𝟎 + 𝑫𝟎 stat.

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Performance for open charm measurements
Two weeks in 2022 (1kHz + LAVD) ≈ 40 000 𝐷 0 + 𝐷 0 decays
reconstructed in 40M central Pb+Pb collisions at 150A GeV/c
LAVD reconstructs 12% out of all 𝐷 0 → 𝜋 + + 𝐾 − decays.
all generated

reconstructed

Based on AMPT one
estimates that fully
corrected results will
cover most of thephase space.

Total systematic uncertainty of 𝐷 0 and 𝐷 0 is expected to be about 10%.
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Uniqueness of NA61 open charm program
Landscape of present and future
heavy ion experiments• LHC and RHIC at high energies:
measurements in small phase space
due to collider geometry and kinematics• RHIC BES collider:measurement not possible due tocollider geometry and kinematics• RHIC BES fixed-target:
measurement require dedicated setup,
not under consideration• NICA (< 80A GeV/c):measurement during stage 2 underconsideration

Only NA61/SHINE is able tomeasure open charm productionin heavy ion collisions in fullphase space in the near future.

• J-PARC (< 20A GeV/c):maybe possible after 2025
• FAIR (< 10A GeV/c):
not possible
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Impact of open charm measurements
central Pb+Pb at 158A GeV/caccuracy of NA61 2020+ result
assuming HSD yield
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Impact of open charm measurements
central Pb+Pb at 158A GeV/caccuracy of NA61 2020+ result
assuming SMES yield
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Impact of open charm measurements
Pb+Pb at 158A GeV/c

𝐽/𝜓 / 𝑐𝑐ҧ accuracyof NA61 2020+ result
assuming
𝑐𝑐ҧ ~ 𝜋and scaling to𝐽/𝜓 / DYfor peripheral collisions

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Summary
NA61 charm program addresses following questions:•What is the mechanism of open charm and 𝐽/𝜓 production?

•How does the onset of deconfinement impact open charm production?

•How does the formation of quark gluon plasma impact 𝐽/𝜓 production?

To answer these questions mean number of charm quark pairs producedin heavy ion collisions will be measured in 2017-2018 and in 2021-2024.
Only NA61/SHINE can perform this measurement in the near future.

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Backup slides

Replacement of the TPC electronics
Will increase the read-out rate by a factor of about 10 (up to 1 kHz)ALICE will transfer to NA61/SHINE its present TPC electronics
that will be replaced during the long shutdown LS2

Present NA61
Front-End Card

ALICE
Front-End Card

ALICE
Front-End Cardon NA61 TPC31Upgrade of the trigger and data acquisition
Need for 1kHz readout frequency

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Search for 𝐷 0 and 𝐷 0preliminary

Huge combinatorial background is suppressed by cuts on:• track transverse momentum• track impact parameter• longitudinal distance between secondary and primary vertices• pair impact parameter
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LHC open charm and J/ψ

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LAVD acceptance35

[Linnyk, Bratkovskaya, Cassing, IJMP E17 1367][Alves et al., [E769 Collab.] PRL 77 (1996) 2388]

Charm in h+A collisions

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NA49 open charm upper limit

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[Linnyk, Bratkovskaya, Cassing, IJMP E17 1367]

HSD predictions38

VD – TPC track matching
Extrapolate SAVD tracks to TPC
volume.
Pre-selection: cut on y-slopes oftracks.

After cuts on dx and dy clear
correlation peaks are seen in dpx
and dpz

Matching with TPC provides:
momenta and PID to VD tracks→ invariant mass distribution

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