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 First application with photons: size of stars (R. Hanbury-Brown, R.Q. Twiss, 1956) In heavy-ion reactions: pions, kaons, … r1r1 r2r2 p1p1 p2p2 ΔpΔp

Bertsch-Pratt Parametrization || in LCMS: R long : longitudinal expansion and lifetime  f R side : transverse size, radial expansion R out : as R side but also duration of emission  Specific predictions of bulk 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 section for any process at the threshold where a coupled channel opens. **Watson(Phys.Rev.88(1952)1163): The enhancement factor for a non- resonant FSI is the same for all channels where chosen pair of particle species appears. R~|f | 2,

Where is Femtoscopy? Signatures of quark-gluon plasma formation in AA Quarkonia 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 AA Quarkonia 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 … Methods Particle yields and spectra Particle ratios Nuclear modification factor Femtoscopy Azimuthal dependence …

R(√S NN, b, A, B, y, m T, , PID) Z. Chajecki, QM05 m t -dependence +( ? ); PID-independence (?)

PRL ‘04 R(√S NN, b, A, B, y, m T, , PID)

R~5fm (?)

STAR preliminary m T (GeV) Z. Chajecki WPCF05 femtoscopy in STAR  p+p and A+A measured in same experiment  great opportunity to compare physics  what causes p T - 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:

Femposcopy at MPD-NICA  1(continued):  A possible explanation: at low energies (say E lab =3-10AGeV) a hadronic system generates a large pressure pushing the system quikly towards a round shape;  But at some energy (say E lab =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 E lab =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 υ 2 originally predicted in (U.Heinz&B.Kolb,Phys.Lett.B469, 557(1999)). The signal in υ 2 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 r out (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 r out and r out /r side 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  M t -scaling test:σ  <<σ others

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 p t А2А2 Fluctons(SRC) Dense baryon system А: С,Ве,Не,… А1А1

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 (N c ) and other participants (N o ) (spectators are not in consideration) one can expect the hierarchy of sizes: r(N c,N c )< r(N o,N o )< r(N c,N o ).  For the dense fermion-rich system is expected the hierarhy of sizes: r(N n,N p )< r(N n,N n ),r(N p,N p ).

Ξ-Ξ- Ξ0Ξ0 -- 0Λ0Λ ++ pn Ξ-Ξ- Ξ0Ξ0 -- 0Λ0Λ ++ pn Baryon matrix coverage CBMNICA-MPD What can be done at CBM better ? 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 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? The  meson 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

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

Stavinskiy,GDRE-Poland p 0 systems Elastic + Inelastic p  0  p  0 (11) n  +  p  0 (21)

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

Spectra v2v2 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)