Thermal Radiation Workshop BNL, December 5-7, 2012 Future Dilepton Experiments Thermal Radiation Workshop BNL, December 5-7, 2012 Itzhak Tserruya

Low-Mass Dileptons at a Glance: Energy Scale Time Scale 15 20 KEK E235 CERES DLS NA60 HADES STAR 90 95 10 00 05 85 PHENIX CBM MPD ? ALICE CERES DLS NA60 HADES STAR 10 158 [A GeV] 17 [GeV] √sNN 200 // PHENIX ALICE 1 CBM MPD = Period of data taking

Outline Top SPS energy Top RHIC energy Low energies A well wrapped story - CERES, NA60 Top RHIC energy Challenging results PHENIX PHENIX - STAR Low energies FAIR, NICA, RHIC, SPS Elementary collisions? Itzhak Tserruya TRW, BNL, Dec. 5-7, 2012

NA60 – low and intermediate masses SPS CERES – low masses NA60 – low and intermediate masses Itzhak Tserruya TRW, BNL, Dec. 5-7, 2012

CERES Pioneering Results (I) Strong enhancement of low-mass e+e- pairs (wrt to expected yield from known sources) First CERES result PRL 75, (1995) 1272 Last CERES result 2000 Pb run PLB 666(2008) 425 Enhancement factor (0.2 <m < 1.1 GeV/c2 ): 5.0 ± 0.7 (stat) ± 2.0 (syst) 2.45 ± 0.21 (stat) ± 0.35 (syst) ± 0.58 (decays)

Dropping Mass or Broadening (I) ? * Interpretation: +-    *  e+e- thermal radiation from HG CERES Pb-Au 158 A GeV 95/96 data dropping  meson mass (Brown et al) * in-medium modifications of : broadening  spectral shape (Rapp and Wambach) * vacuum ρ not enough to reproduce data Itzhak Tserruya TRW, BNL, Dec. 5-7, 2012

Dropping Mass or Broadening (II) ? * Interpretation: +-    *  e+e- thermal radiation from HG CERES Pb-A 158 A GeV 2000 data * vacuum ρ not enough to reproduce data * in-medium modifications of : broadening  spectral shape (Rapp and Wambach) dropping  meson mass (Brown et al) Data favor the broadening scenario. Itzhak Tserruya TRW, BNL, Dec. 5-7, 2012

Quark – Hadron Duality R. Rapp In-medium + - ann. rates  perturbative qbarq ann. rates quark – hadron duality down to m ~ 0.5 GeV/c2 Kämpfer calculations: Thermal radiation from the plasma or just a parametrization of the e+e- yield inspired by quark-hadron duality? Itzhak Tserruya TRW, BNL, Dec. 5-7, 2012

NA60 Low-mass dimuons Real data ! Superb data!!! In+In 158 A GeV Excess shape in agreement with broadening of the  (Rapp-Wambach) Mass resolution: 23 MeV at the  position Mass shift of the  (Brown-Rho) ruled out S/B = 1/7 Itzhak Tserruya TRW, BNL, Dec. 5-7, 2012 Melting of the ρ?

The IMR Excess Quark-Hadron duality? NA60 demonstrated that IMR excess is due to a prompt source. Renk/Ruppert, PRL 100,162301 (2008) Hees/Rapp, PRL 97, 102301 (2006) IMR excess can be explained by: hadronic processes, 4 … partonic processes, qq annihilation Quark-Hadron duality? Itzhak Tserruya TRW, BNL, Dec. 5-7, 2012

Acceptance corrected invariant mass spectrum Mass spectrum corrected for acceptance in m - pT Eur. Phys. J. C 59 (2009) 607 LMR: thermal radiation from HG p+p-  r  m+m- IMR: Thermal radiation from HG: p a1  m+m- (Hees/Rapp) Or Thermal radiation from QGP qq  m+m- (Renk/Ruppert) Quark-Hadron duality?

Fit in 0.5<PT<2 GeV/c (as in LMR analysis) pT distributions Intermediate mass region Low-mass region Fit in 0.5<PT<2 GeV/c (as in LMR analysis) mT spectra exponential inverse slopes do not depend on mass. mT spectra exponential inverse slopes depend on mass.  Radial Flow Thermal radiation from partonic phase Elliptic flow? Itzhak Tserruya

SPS top energy summary LMR: thermal radiation from HG p+p-  r  m+m- Eur. Phys. J. C 59 (2009) 607 LMR: thermal radiation from HG p+p-  r  m+m- Resonances melt as the system approaches CSR IMR: Thermal radiation from QGP qq  m+m-

RHIC Itzhak Tserruya TRW, BNL, Dec. 5-7, 2012

Low-mass e+e- Pairs: Prospects at RHIC At SPS energies, the -meson broadening, that explains both the CERES and NA60 data, relies on a high baryon density. R. Rapp nucl-th/0204003 What was expected at RHIC? 102 110 Total baryon density 8.6 21.4 33.5 85 p – p Participants nucleons (p – p )A/Z 20.1 80.4 6.2 24.8 dN( p ) / dy Produced baryons (p, p, n, n ) RHIC (Au-Au) SPS (Pb-Pb) Baryon density is almost the same at RHIC and SPS (the decrease in the participating nucleons transported to mid-rapidity is compensated by the copious production of nucleon-antinucleon pairs) Strong enhancement of low-mass pairs predicted to persist at RHIC Itzhak Tserruya TRW, BNL, Dec. 5-7, 2012

Dileptons in PHENIX: Au+Au collisions PRC 81, 034911 (2010) LMR: Strong enhancement at m= 0.15 – 0.75 GeV/c2. min. bias 4.7 ± 0.4 (stat.) ±1.5 (syst.) central collisions 7.6 ± 0.5 (stat.) ± 1.3 (syst.) Enhancement down to very low masses Enhancement concentrated in central collisions IMR: agreement with pp charm contribution scaled with Ncoll

Comparison to theoretical models Models that successfully described the SPS data fail in describing the PHENIX results

All this is very different from the SPS results New source? mT distribution of low-mass excess Excess present at all pair pT but is more pronounced at low pair pT The excess mT distribution exhibits two clear components It can be described by the sum of two exponential distributions with inverse slope parameters: T1 = 92  11.4stat  8.4syst MeV T2 = 258.3  37.3stat  9.6syst MeV PHENIX All this is very different from the SPS results New source? Itzhak Tserruya TRW, BNL, Dec. 5-7, 2012

Dileptons in STAR Itzhak Tserruya TRW, BNL, Dec. 5-7, 2012

STAR Dileptons in Au+Au collisions STAR Preliminary STAR Preliminary LMR: clear enhancement wrt to cocktail little centrality dependence IMR: no clear picture LMR (MB): S/B = 1/200 Itzhak Tserruya TRW, BNL, Dec. 5-7, 2012

PHENIX vs. STAR Large quantitative differences Minimum Bias Enhancement factor in 0.15<Mee<0.75 Gev/c2 Minimum Bias Central collisions PHENIX 4.7 ± 0.4 ± 1.5 7.6 ± 0.5 ± 1.3 STAR 1.40 ± 0.06 ± 0.38 1.54 ± 0.09 ± 0.45 Large quantitative differences Itzhak Tserruya

Compare to Rapp, Wambach, v. Hees STAR central 200 GeV Au+Au hadronic cocktail (STAR) Ralf Rapp (priv. comm. to STAR) Complete evolution (QGP+HG): cocktail + QGP + HG: Reasonable agreement with data Itzhak Tserruya TRW, BNL, Dec. 5-7, 2012

Dileptons in PHENIX: Au+Au collisions Min bias Au+Au √sNN = 200 GeV Phys. Rev. C81, 034911 (2010) Integral: 180,000 above p0: 15,000 S/B ≈ 1/200  large statistical and large systematic errors Cocktail / B ≈ 1/1000 To improve the measurement PHENIX developed a Hadron Blind Detector

Run-9 p+p dileptons with the HBD Fully consistent with published result PR C81, 034911 (2010) Improvement in S/B by a factor of 5-10. Expected to do better in final analysis Provide crucial proof of principle and testing ground for understanding the HBD Itzhak Tserruya TRW, BNL, Dec. 5-7, 2012

Run-10 Au+Au dileptons at √sNN=200 GeV with the HBD Peripheral Semi-peripheral Semi-central + Itzhak Tserruya TRW, BNL, Dec. 5-7, 2012

Run-10: Data/Cocktail Comparison Run10 – Run4 LMR (m = 0.15 – 0.75 GeV/c2) Hint of enhancement for more central collisions Not conclusive given the present level of uncertainties IMR (m = 1.2 – 2.8 GeV/c2) Similar conclusions for the IMR Run 10 consistent with published Run4 results

Future LMR: Solve the PHENIX - STAR discrepancy HBD results in central Au+Au collisions IMR: higher precision data needed Higher statistics and direct measurement of charm contribution Fill the gap between top SPS and top RHIC energy Preliminary STAR results Itzhak Tserruya TRW, BNL, Dec. 5-7, 2012

Dileptons with sPHENIX Hadron Calorimeter Electromagnetic Calorimeter Solenoid 2 T 1.4m Use inner region for dilepton measurement ? Itzhak Tserruya TRW, BNL, Dec. 5-7, 2012

Fast TPC + active beam pipe TPC / HBD Fast TPC + active beam pipe CsI Readout Plane active beam pipe Pre-Shower / DIRC 0.7 m 0.1 m EMCal Dy = 2 Solenoid with < 1 T TPC Readout Plane fast TPC Readout Pads TPC provides tracking and eid by dE/dx HBD provides eid GEMs are used for both TPC and HBD Silicon strip with sf ~100 mm dp/p << 1%p Tracking with TPC Itzhak Tserruya

Future LMR: Solve the PHENIX - STAR discrepancy HBD results in central Au+Au collisions IMR: higher precision data needed Higher statistics and direct measurement of charm contribution Fill the gap between top SPS and top RHIC energy Preliminary STAR results Dilepton v2 Itzhak Tserruya TRW, BNL, Dec. 5-7, 2012

Dileptons v2 First measurements by STAR Dilepton v2(mee) and v2(pT) results consistent with simulations based on hadronic sources

Lower – energies: Itzhak Tserruya TRW, BNL, Dec. 5-7, 2012

Low energies: testing the model Explanations of CERES and NA60 results rely on the high baryon density rather than the temperature of the system. Lower energies  controlled change of conditions: higher baryon density and lower temperature Phys. Rev. Lett. 91, 042301 (2003) Only available test: CERES measurements at 40 AGeV. Enhancement factor: 5.9 ± 1.5 ± 1.2 ± 1.8 (cocktail) Itzhak Tserruya TRW, BNL, Dec. 5-7, 2012

Highest baryon density RHIC SPS Collider FAIR, NICA Fixed target Freeze-out conditions

Multi-Purpose Detector (MPD) at NICA 2-nd stage IT,EC-subdetectors, Forward tracking chamber(GEM,CPC) 1-st stage barrel part (TPC, Ecal, TOF) + ZDC,FFD, BBC, magnet, … 3-d stage F-spectrometers (optional ?) Toroid 3 stages of putting into operation. First stage: 2017? Itzhak Tserruya TRW, BNL, Dec. 5-7, 2012

Compressed Baryonic Matter (CBM) at FAIR tracking, momentum determination, vertex reconstruction: radiation hard silicon pixel/strip detectors (STS) in a magnetic dipole field hadron ID: TOF (& RICH) photons, p0, h: ECAL PSD for event characterization high speed DAQ and trigger → rare probes! electron ID: RICH & TRD  p suppression  104 muon ID: absorber + detector layer sandwich  move out absorbers for hadron runs ECAL TOF TRD RICH absorber + detectors STS + MVD magnet

LVM in pA Collisions Cold nuclear matter at highest baryon density Should broadening effects be visible? Itzhak Tserruya TRW, BNL, Dec. 5-7, 2012

KEK E235 p+C, Cu @ 12 GeV PRL 96, 092301 (2006) PRL 98, 042501 (2007) Interpretation: masses drop by 9.2% (,) and 3.4% (ϕ) at normal nuclear matter density CBELSA/TAPS: No mass shift. Shape consistent with ω in-medium broadening CLAS: No effect. Results reproduced by transport model using vacuum mass values of ,  and . TRW, BNL, Dec. 5-7, 2012

Proposed experiment: JPARC – E16 30/50 GeV p beam on Cu, Pb targets Tracking: GEM, eid: HBD, EMCal a Itzhak Tserruya TRW, BNL, Dec. 5-7, 2012

Summary SPS energies: Consistent and coherent picture Low-mass pair enhancement: thermal radiation from the HG Approach to CSR proceeds through broadening (melting) of the resonances IMR enhancement: thermal radiation from partonic phase Missing: elliptic flow measurements Higher energies SPS  RHIC: New source at top RHIC energies? Solve the PHENIX–STAR discrepancy - HBD results in central Au+Au collisions IMR: need higher precision data: higher statistics and direct measurement of charm contribution Fill the gap between top SPS and top RHIC energy – STAR, sPHENIX? Lower energies: explore the phase space of highest net baryon density CBM at FAIR? MPD at NICA? SPS? RHIC? LVM in pA collisions: cold nuclear matter at the highest baryon density JPARC E16 experiment Itzhak Tserruya TRW, BNL, Dec. 5-7, 2012