Searching for Strange Quark Matterwith the CMS/CASTOR Detector at the

LHC

P. Katsas, A.D. Panagiotou, E. Gladysz

for the CMS/CASTOR Group

http://cmsdoc.cern.ch/castor/

CMS-HI meeting, 23-9 2006

● Motivation: Unconventional Events in Cosmic Rays

● Phenomenological Models & MC Simulations

● “Strangelet” Identification Analysis● Summary

Outline

Homogeneous thick lead chamber

Centauro

Hadron – Rich CR Events

Normal

Measurement settings:

100 μm shower core diameter threshold ~ 3 TeV

(Strangelet ?)

3.6 λI

3.2 λI

3.6 λI

1.5 λI Hadron limit

Hadron limit

CENTAURO FIREBALL EVOLUTION

56A + 14N

u, d g s s

QUARK MATTER FIREBALL

in the baryon-rich fragmentation region

High q suppresses production

of (u u) , (d d), favoring g s s

K+, K0 carry out:

strangeness, positive charge, entropy

CENTRAL COLLISION

at the top of the atmosphere

Ep ~ 1740 TeV

u, d,s

K+

K 0

(u s)

(d s)

u

s

d

(pre-equilibrium) KAON EMISSION

SQM FIREBALL

EXPLOSION

StrangeletHG

...

HG

B¼ < 190 MeV B¼ > 190 MeV

Stabilizing effects of s quarkslong lived state

~75 non strangebaryons + strangelet

(A ~ 10 -15)

Strangenessdistillationmechanism

C. Greineret al., Phys. Rev. D38

(1988)2797

Estimates for Centauro at LHC

• Energy density ε ~ 3 - 25 GeV/fm 3, • Temperature T ~ 130 - 300 MeV• Baryochemical potential µb ~ 0.9 - 1.8 GeV/fm3

CNGEN Centauro & Strangelet

Generator

Phys. Rev. D45(1992)3134 Astroparticle Phys. 2(1994)167 Astroparticle Phys. 13(2000)173

Phys. Atom. Nucl. 67(2004)396

anti-

N = 2352N = 108

Multiplicity in CASTOR Acceptance

CENTAURO HIJING

Low multiplicity High multiplicity mostly baryons + kaons dominated by pions

Simulations - CNGEN

5.2 < < 6.5

T = 250 MeV, q= 600MeV, ystop = 3.0 idpartidpart

CASTOR

Probability of Centauro & Strangelet Detection

CASTOR

~ 60 % of Centauro decay products and ~ 10% of Strangelets within CASTOR acceptance

= 9 GeV/fm3, T = 250 MeV, q= 330 MeV, ystop = 3.0

Estr (GeV)

5.2< < 6.5

MC Radial Acceptance of CASTOR

Strangelets from Centauro Decay

∆ystop ~ 2 – 3.5

5.2 <

Expected at LHC:● Energy densities up to

є ~ 25 GeV/fm3

● ∆ystop ~ 2 - 3.5

HIJING,VENUS

● ∆ystop ~ 2.3

BRAHMS-RHIC

several to ~ 25% strangelets with energies E > 7 TeV, sufficiently high to be detected.

T = 350 MeVT = 300 MeVT = 250 MeV

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

str31

0

mμμπ

2a12

A3πArR

231

str03

1

W

NWWstr

ArA1.12π

mAλ

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 O(αs) corrections to the properties of SQM.

ss s

Unstable Strangelet in Pb chamber

MC Simulation

7 Neutrons

Similarity between the experimental data (squares) and simulated cascades produced by a bundle of seven neutrons (full histogram).

(a) Distribution of mutual distance between the consecutive maxima; (b) Distribution of ratios of the energy contained in the particular maxima

to the average energy of the humps.

Comparison Data with Simulation

MC - Stable Strangelet in CASTOR

CASTOR Geometry configuration

1 layer: 5mm W+2mm quartz plate ~2.4 X0

1 RU = 7 layers per readout unit

16 (in x 18 (in z) readout channels

Total depth: ~ 10.5 int

Low Energy Strangelets (~5 TeV)

may be seen above background.HIJING

HIJING

Depth

Depth

A=15, E=7.5 TeV

A=10, E=5 TeV 60 pions, 1TeV each

Stable Strangelet in CASTOR

Full CASTOR Calorimeter

Stage I

Stage II

Segmentation: 14(depth) x 16(azimuth) = 224 channels

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HIJING Pb+Pb Event at √s = 5.5 TeV

Etot ~ 130 TeV ~ 8 TeV/sector N < 100/sector

GeV

GeVη

η

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Fluctuations in Cascade Profile in Sectors

Calorimeter Depth (RUs)

En

ergy

HIJING

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Fluctuations in Energy Distribution in SectorsE

n. D

istr

ibu

tion

in s

ecto

r / A

vera

ge E

n. D

istr

ibut

ion

1

16

HIJING

2

15

Strangelet signatures

Azimuthal asymmetryin energy deposition

FluctuationsLongitudinaltransition curves

sd

iE

EE

Event-by-event analysis Analysis procedure in 2 steps:

average distribution energy distribution per RU

Large magnitude of energyfluctuations in RUs manifestabnormal transition curves

nsfluctuatio

Strangelet identification & Analysis

(i = 1 – 16 sectors)

<E> = mean energy in sectors

nsfluctuatio

σsd = standard deviation of the distribution of the energies Ei

Analysis of HIJING Event

Need to analyze 104 events

HIJING Strangelet in one sector

Energy in RUs Energy in RUs

Energy distributions in CASTOR

(Depth) (Depth)

A = 15 E = 7.5 TeV

Average of 16 Sectors

En

ergy

RU RUSector Sector

Total Energy in Sectors Total Energy in Sectors

<E>

Pb+Pb HIJING + Strangelet

Pb+Pb HIJING + Strangelet Cascade Profile in Sector

Depth

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Analysis with Strangelet

Estr = 7.5 TeV Estr = 10 TeV

EM-cutonly H-sectionEM+H section

sector containingStrangelet + HIJING sectors containing

HIJING Pb+Pb

σE

σfluctuations

Estr = 7.5 TeV

Strangelet in between two Sectors Energy Distribution in Sectors

Sectors with Strangelet

~ 14% with Ei/Ej = 50/50 – 75/25

Estr = 7.5 TeV

<HIJING><HIJING>

Strangelet in between two Sectors Transition Curves

Depth Depth

HIJING + Strangelet

Analysis with Strangelet in two Sectors

EM-cut

Sectors with Strangelet

Strangelets of various Energies

15 TeV

10 TeV

7.5 TeV

EM-cut

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Comparison of Observed and Input MC Strangelet Efficiency of Identification

Eobs ~ 97%

Observed Strangelet ≡ Average Energy distribution of mixed event – Energy distribution in sector containing Strangelet

• The probability for a hadron-rich ‘Centauro-type’ event, estimated from statistics of Chacaltaya and Pamir experiments for cosmic ray families with visible energy greater than 100 TeV, is about 3%.

• In about 10% of these hadron-rich events, strongly penetrating cascades, clusters, or ”halo” were observed. We assume the total probability for “Long Flying Component” (Strangelet?) production in central nucleus-nucleus collisions to be approximately: 0.03 x 0.1 ~ O(10−3).

• At LHC kinematics, the percent of Strangelets falling in CASTOR phase space is ~ 10% of total number of Strangelets produced in central Pb-Pb collisions. This quantity depends on the mass and energy of the Strangelet, as calculated by the “Centauro model” MC code CENGEN.

• A rough estimation of the total probability for Strangelet production and detection in CASTOR is:

PCASTOR strangelet ≈ 10−3 × 0.1 ≈ O(10−4)

• This number, even if it is uncertain by an order of magnitude down, is a very large number !

Cross Section Estimation for Strangelets

Characteristics of a “Strangelet event”:

1. Sector(s) with much higher energy than the average.

2. Strong fluctuations in the longitudinal cascade profile of the sector.

3. Large Ehad/Eem for the event (Hadron-rich event).

Summary

Astr = 15 Estr = 5 TeV