Searching for Deconfined Quark-Matter in HI collisions at the CERN LHC with CMS/CASTOR

NuPECC Annual Meeting Athens, 8 October, 2010

Apostolos D. PanagiotouCMS/Athens – CASTOR group

Heavy Ion Physics at the LHC with CMS

Central region

Forward region

30%

5.5 TeV

Energy & Particle Pseudorapidity Distributions

Net Baryon Number Pb+Pb @ 2.8 TeV

All of Net Baryon Number in forward region High Baryochemical Potential Lower temperature

A

(Strangelet ?)

3.6 λI

3.2 λI

3.6 λI

1.5 λI Hadron limit

Hadron limit

What is a “Strangelet” ?

10

“Stable” Strangelet interaction in CASTORMC-algorithm

Strangelet is considered with radius:

Mean interaction path:

Strangelets passing through the detector collide with W nuclei: Spectator part is continuing its passage. Wounded part produces particles in a standard way.

Particles produced in successive interactions initiate electromagnetic-nuclear cascades. Process ends when strangelet is destroyed.E. Farhi, R. Jaffe, Phys.Rev.D30(1984)2379; M. Berger, R. Jaffe, Phys.Rev.C 35(1987)213, G.Wilky, Z.Wlodarczyk, J.Phys.G22(1996)L105; E. Gładysz, Z. Włodarczyk, J.Phys.G23(1997)2057

31

23223s

str310

mμμπ2a12

A3πArR

231str0

31W

NWWstr

ArA1.12πmAλ

nstrstr NAA'

The rescaled r0 is determined by the number density of the strange matter: n = A/V = (1/3)(nu+nd+ns)where ni=- ∂Ωi/∂μi; Ω(mi,μi,αs), taking into account the QCD corrections O(αs) to the properties of SQM.

ss s

11

31

23223s

str310

mμμπ2a12

A3πArR

231

str031

W

NWWstr

ArA1.12πmAλ

Scaled Radius & Mean Free Path of Strangelets vr μq

Collapsed nucleus

λWπ ~ 7 cm

quark quark

28-05-201012/12/0809/12/200827/10/2008

12

MC simulation of Strangelets in CASTOR

13

1. Sector with much higher energy than the average: Strong azimuthal asymmetry in energy deposition

2. Strong penetration of the longitudinal cascade in a sector:Strong fluctuations in longitudinal transition curves

3. Much smaller EEM / EHAD compared to HIJING

4. Appearing in a very low multiplicity event compared to HIJING

Characteristics of a “LFC” Event

28-05-201012/12/0809/12/200827/10/2008

141414

CMS/CASTOR Calorimeter

Front View

Side View

LFC Signatures

Azimuthal asymmetryin energy deposition

Fluctuations longitudinaltransition curves

sd

iE

EE

Event-by-event analysis in 3 steps:

average distribution energy distribution per RU

Large magnitude of energyfluctuations in RUs manifestin abnormal transition curves

L. F. C. Identification Analysis

(i = 1 – 16 sectors)<E> = mean energy in sectors

nsfluctuatio

σsd = standard deviation of the distribution of the energies Ei

Examine Ratio EEM / EHAD of events

1

3

2

Analysis (Ι)“LFC signature” Azimouthal Energy

distribution

Cascade Energy distribution

- Event-by-event- Sector-by-sector(Central Pb+Pb collisions, b=0)

Analysis (Ι)“Strangelet

signature”Azimouthal Energy

distribution

Cascade Energy distribution

- Event-by-event- Sector-by-sector(central Pb+Pb collisions, b=0)

Select φ-sector containing LFC

Fluctuations on the (fa,fl) plane

Statistical fluctuations of HIJING events with similar characteristics Strangelets with higher energies are separated from conventional HIJING

events Distinction of conventional events with similar fluctuations

EEM/EHD

HIJING(2k events)

StrangeletsE=6-15 TeV

Analysis (ΙI)

19

Analysis (ΙII)

20

Analysis (ΙII)

21

• Probability for a hadron-rich ‘Centauro-type’ event is about 3%, estimated from statistics of Chacaltaya and Pamir experiments for cosmic ray families with visible energy greater than 100 TeV.• In about 10% of hadron-rich events, strongly penetrating cascades, clusters, or “halo” were observed. Assume total probability for “Long Flying Component” (LFC) production in central nucleus-nucleus collisions to be approximately: 0.03 x 0.1 ~ O(10−3).• At LHC kinematics, the percent of LFCs in CASTOR phase space is at least ~ 1% of total number of LFCs produced in central Pb-Pb collisions, depending on their mass and energy (CENGEN). • An order of magnitude estimation of the total probability for LFC detection in CASTOR is:

PCASTORLFC ≈ 10−3 × 0.01 ≈ O(10−5)

Cross Section Estimation for LFC

ΝLFC ~ 1-10 in 4 wks Pb+Pb (5M central events in 2010)