Femtoscopy status and the first glance on perspectives of

femtoscopy at CBM

0. Introduction (first slide)

1. What is femtoscopy (slides 2-6)

2. Some important results(7-10)

3. Proposed femtoscopy measurements for NICA(11-21)

4. Proposal for CBM(22-24)

5. Conclusion (25)

A.Stavinskiy, ITEP, CBM-collaboration meeting, Darmstadt, april 2010

Interferometry

Bose-Einstein statistics of identical bosons leads to short-range correlations in momentum space

)(

)()(

),(),(

21

2111

212212

pp1

pPpP

ppPppC

First application with photons: size of stars(R. Hanbury-Brown, R.Q. Twiss, 1956)

In heavy-ion reactions: pions, kaons, …

fmMeV/c

p

197

p

cr

r1

r2

p1

p2

Δp

Bertsch-Pratt Parametrizationoutsidelongoutsidelong21 RRRqqqqpp ,,),,(

| |

in LCMS:

0pp 2z1z ,,

Rlong : longitudinal expansion and lifetime f

Rside : transverse size, radial expansionRout : as Rside but also duration of emission

Specific predictions ofbulk collective flow:

• space-momentum (x-p) correlations

• faster (high pT) particles come from

•smaller source

•closer to “the edge”

Non identical* Wigner(Phys.Rev.73(1948)1002):A casp appears in the cross sectionfor any process at the thresholdwhere a coupled channel opens.

**Watson(Phys.Rev.88(1952)1163):The enhancement factor for a non-resonant FSI is the same for allchannels where chosen pair ofparticle species appears.

f 1 a rk2 2 ik 1R~|f |2,

Where is Femtoscopy?

Signatures of quark-gluon plasma formation in AAQuarkonia suppression(evidence for deconfinement or dynamical ionization)

Restoration of chiral symmetry(vector meson in dense matter)

Radiation of plasma(direct photon and thermal dileptons)

Remnants of hadronization( strangeness enhancement)

Anomalous increase in pressure(collective flow effects)

Creation of high temperature(particle spectra,ratios)

…

Femtoscopy(anomalous increase in volume(time))

Segmentation fault !

Where is Femtoscopy?

Signatures of quark-gluon plasma formation in AAQuarkonia suppression

Restoration of chiral symmetry

Radiation of plasma

Remnants of hadronization

Anomalous increase in pressure(flow effects)

Anomalous increase in volume (time)

Creation of high temperature

…

MethodsParticle yields and spectra

Particle ratios

Nuclear modification factor

Femtoscopy

Azimuthal dependence

…

R(√SNN, b, A, B, y, mT, , PID)

Z. Chajecki, QM05

mt-dependence +(?); PID-independence (?)

PRL 93 012301 ‘04

R(√SNN, b, A, B, y, mT, , PID)

R(√SNN, b, A, B, y, mT, , PID)

R~5fm (?)

STAR preliminary

mT (GeV) mT (GeV)

Z. Chajecki WPCF05

femtoscopy in p+p @ STAR p+p and A+A

measured in same experiment

great opportunity to compare physics

what causes pT-dependence in p+p?

same cause as in A+A?

Femposcopy at MPD-NICA

1.M.Lisa(OhioUn.): STAR has measured oscillation if pion radii

relative to the second-order event plane (Phys.Rev.Lett.93,012301(2004)); source shape is found to be extended out of the reaction plane; it is, however, less anisotropic, than initial source defined by overlap of the colliding nuclei, reflecting evolution over time in preferential in-plane expansion.

Since the lifetime(and elliptic flow) increase with energy, one naively expect that anisotropy becomes less and less and may even become in-plane extended(U.Heinz&B.Kolb,Phys.Lett.B542,216(2002))

Femposcopy at MPD-NICA 1(continued):M.A.Lisa&S.Pratt,arXiv:0811.1352

Femposcopy at MPD-NICA

1(continued): A possible explanation: at low energies (say Elab=3-10AGeV)

a hadronic system generates a large pressure pushing the system quikly towards a round shape;

But at some energy (say Elab=20AGeV), a threshold energy required to generate a phase transition is crossed, characterized by a finite latent heat; this generates a “soft point” in the equation of state and the push towards a round state is stalled briefly

As the energy increases beyond this threshold, the time spent in the “soft state”grows, and the “out-of-plane-ness” grows with energy (until, say Elab=70AGeV)

Then the system spends most of its time in the QGP phase, and “out-of-plane-ness”again decreases with energy

Direct analog for υ2 originally predicted in (U.Heinz&B.Kolb,Phys.Lett.B469, 557(1999)). The signal in υ2 has not been observed, but the spatial anisotropy probed by femtoscopy is weighted in the time evolution differently

Femposcopy at MPD-NICA 2.R.Lednicky(JINR):

It is well-known that rout(parallel to the pair transverse velocity component of the emission region size) is sensitive to the duration of particle emission

When the hot and dense system created in the collision process passes through the partonic phase back to the hadronic one (1-st order phase transition), the latent heat is expected to increase the emission duration, but

The corresponding increase of rout and rout/rside ratio has not been observed. Why?

Femposcopy at MPD-NICA

2(continued): Partoinic phase is not dominant one (its

fraction in the central PbPb collisions at Elab = 20 and 160 A GeV is estimated on the level of ~10% and 40% (W.Cassing &E.Bratkovskaya,

Symp.on The Phys.of Dense Bar.Matt., Darmstadt,2009) In the presence of two or more essentially

different radii the single-(3D)Gaussian fit of R is dominated by the smaller scales

Femposcopy at MPD-NICA

2(continued): Proposed solution: 2D-*(3D-) fit (with up to

8 parameters taking into account two sets of the three radii and the corresponding fractions)

The analysis of R of various particle species(including nonidentical particles) to better control the contribution of the non-lifetime effects(resonance decays, flow, rescattering etc.)

Femposcopy at MPD-NICA

3.Kaon femtoscopy(MSU(L.Malinina)-ITEP(K.Mikhailov,A.S.)

Partoinic phase is not dominant one. Strangeness enhancement is one of the

QGP signatures Partonic effects better to measure in

strange sector(K,φ)

Femposcopy at MPD-NICA 3 continued:

Azimuthal femtoscopy are mesured for only Mt-scaling test:σ<<σothers

Femposcopy at MPD-NICA 4.Femtoscopy with rare trigger

(selection criteria,ITEP group) The main idea: to study light ions collisions

(from HeHe to CC) with high pt midrapidity trigger. The maximum possible trigger momentum corresponds selects multinucleon interaction. One can expect dense real multinucleon (6-7 nucleons) system in the final state.

Femposcopy at MPD-NICA

4(continued):

,,o,… high pt

А2

Fluctons(SRC)

Dense baryon system

А: С,Ве,Не,…

А1

Femposcopy at MPD-NICA

4(continued) Expected clusterisation of baryons in coordinate space

and increase of cluster throwout time for that claster could be experimentally tested using femtoscopy method.

Dividing secondary baryons into participants of dense cluster formed in flucton-flucton interaction (Nc) and other participants (No) (spectators are not in consideration) one can expect the hierarchy of sizes:

r(Nc ,Nc )< r(No ,No )< r(Nc ,No ). For the dense fermion-rich system is expected the hierarhy of sizes:

r(Nn ,Np )< r(Nn ,Nn ),r(Np ,Np ).

Ξ- Ξ0

- 0

Λ+

p n

Ξ- Ξ0

- 0

Λ+

p n

Baryon matrix coverage

CBMNICA-MPD

What can be done at CBM better ?1-4 - due to much higher statistic!

What can be done may be only at CBM?

1.γγ-femtoscopy. Reason for that: penetrating mode

provides information on the early stage of the process;

Small effect: direct photon contribution ~10% and correlation effect ~1%(WA98)

Small q -> efficiency problem(M+Sreport at CBM meeting) –> conversion method-10-2 factor for statistic

What can be done may be only at CBM?

2.Resonance (ωω,φφ,K*K*) femtoscopy. Reason for that:

hadronization process study; l ~ 10 fm; is it sufficiently long trajectory to create interferometry correlations?

Vector meson production study(for ωω,φφ) Strangness production study(for φφ,K*K*)

φφ: S/B(inclusive)~10%(charge kaons mode)→S/B(correlations)~1%; spin factor*branching~0.1

ωω; +-~1.7%

Conclusions

CBM has a great potential for femposcopy

Extra slides

Does we really need it?

Themeson was proposed in the middle of 80’(Koch,Muller,Rafelski PR142,ShorPRL54) as one of the most promising QGP messengers because of the following reasons: an enhancement of –meson, as well as other strange

hadrons in QGP phase interaction cross section is small and will keep

information about the early hot and dense phase meson spectrum is not distorted by feeddown from

resonance decays strangeness local conservation for

Stavinskiy,GDRE-Poland-210207

Stavinskiy,GDRE-Poland-210207

C L A S p r e l i m i n a r y

Stavinskiy,GDRE-Poland-210207

p0 systems

Elastic + Inelastic

p0p0 (11)

n+p0 (21)

Definitions

A.M.Poskanser&S.A.Voloshin, Methods for analyzing anisotropic flow in relativistic nuclear collisions;Phys.ReV.C58,1671(1998)

Spectra

v2

HBT

Momentum observables &Femposcopy

the pt dependence of azimuthally-integrated femtoscopic radii gives access to the geometric substructure generated by radial flow;

Femtoscopic radii measured relative to the first- and second-order event plane are the spatial analogs of directed and elliptic flow

F.Retiere&M.Lisa,Phys.ReV.C70,044907(2004);M.A.Lisa,U.Heinz&U.Wiedemann,Phys.Lett.B489,287(2000)