1. Jornadas LIP, Dez. 2005 P. Martins - CFTP-IST The NA60 Silicon Vertex Telescopes Dimuon measurements Dimuon measurements Vertex telescope used in: Vertex telescope used in: Ions runs (2003) Ions runs (2003) Protons runs (2004) Protons runs (2004)

2. Jornadas LIP, Dez. 2005 2 P. Martins - CFTP-IST Measuring dimuons Signals within reach: Signals within reach: Vector mesons ( η, ρ, ω, ϕ, J/ψ and ψ’ ) Vector mesons ( η, ρ, ω, ϕ, J/ψ and ψ’ ) Open charm simultaneous semi-leptonic decays Open charm simultaneous semi-leptonic decays Drell-Yan quark anti-quark annihilation Drell-Yan quark anti-quark annihilation Background Background Simultaneous π and K decays Simultaneous π and K decays

3. Jornadas LIP, Dez. 2005 3 P. Martins - CFTP-IST Degraded dimuon mass resolution Large combinatorial background Cannot distinguish prompt muons from decay muons Measuring dimuons Muon Other Energy loss Multiple scattering hadron absorber muon trigger and tracking target beam magnetic field or ?

4. Jornadas LIP, Dez. 2005 4 P. Martins - CFTP-IST 2.5 T dipole magnet hadron absorber Improved dimuon mass resolution Reduced combinatorial background Origin of muons can be accurately determined Matching in coordinate and momentum space targets beam tracker Measuring dimuons in NA60 muon trigger and tracking magnetic field Muon Other or ! vertex telescope

5. Jornadas LIP, Dez. 2005 5 P. Martins - CFTP-IST Requirements on the telescope A vertex telescope for heavy-ion running High-energy (nuclear) collisions Dimuon production Small cross-section High statistics Selective dimuon trigger Radiation tolerance Fast read-outGranularity High multiplicity environment High precision Fixed-target Segmented target As a function of centrality Radiation-hard zero degree calorimeter High luminosity

6. Jornadas LIP, Dez. 2005 6 P. Martins - CFTP-IST 8” read-out chip wafer Silicon pixel detectors Pixel sensor 12.8  13.6 mm 2 active area 256  32 cell matrix 50  425 µm 2 cell size ALICE1LHCB read-out chip Operated at 10 MHz Radiation tolerant up to ~ 30 Mrad 32 columns parallel read-out + 5” sensor wafer (layout) 25 µm solder bump =

7. Jornadas LIP, Dez. 2005 7 P. Martins - CFTP-IST 800’000 channels, 50  425 µm 2 pixel size 12 tracking points with good acceptance 9 X (bending plane, |B| = 2.5 T) 3 Y (non-bending plane) 8 “small” 4-chip planes 8 “big” 8-chip planes ~ 2 – 3 % X 0 per plane The silicon pixel vertex telescope beam tracker targets

8. Jornadas LIP, Dez. 2005 8 P. Martins - CFTP-IST Vertexing performance Data collected in October 2003 with 158 GeV Indium beam Z-vertex Z-vertex determination from pixel telescope σ z ~ 200 µm Beam tracker sensors Target box windows In targets Transverse coordinates Transverse coordinates measured by the vertex telescope and the beam tracker σ bt ~ 20 µm → σ vt ~ 12 µm 10 20 30 0 σ(µm) VT Vertex resolution (for σ BT = 20 µm) Dispersion between BT track and VT vertex

9. Jornadas LIP, Dez. 2005 9 P. Martins - CFTP-IST Leakage current vs. time Radiation tolerance Hit efficiency vs. bias voltage inner region needs increased bias voltage after 4 weeks running 158 GeV SPS Indium beam in October 2003 ~ 4  10 12 ions delivered over 5 weeks Performance was closely monitored Sensor type inversion was expected, seen and understood The detector was re-used in 2004 for proton running strong temperature dependence increase with integrated dose (and luminosity)

10. Jornadas LIP, Dez. 2005 10 P. Martins - CFTP-IST Hit maps from a bias voltage scan after 4 weeks Type inversion p+p+ n n+n+ Active volume 150 V “Brand new” pixel sensor

11. Jornadas LIP, Dez. 2005 11 P. Martins - CFTP-IST Hit maps from a bias voltage scan after 4 weeks Type inversion 100 V

12. Jornadas LIP, Dez. 2005 12 P. Martins - CFTP-IST Hit maps from a bias voltage scan after 4 weeks Type inversion 80 V

13. Jornadas LIP, Dez. 2005 13 P. Martins - CFTP-IST Hit maps from a bias voltage scan after 4 weeks Type inversion p+p+ n n+n+ irradiation n+n+ p p+p+ Active volume Pixels disconnected from the active volume do not work Less irradiated zones are still connected for the same bias voltage n+n+ p 60 V

14. Jornadas LIP, Dez. 2005 14 P. Martins - CFTP-IST Hit maps from a bias voltage scan after 4 weeks Type inversion 50 V Pixels at small radii receive more fluence : Lowering the bias voltage leaves an ever larger area not fully depleted (i.e. very inefficient) Lowering the bias voltage leaves an ever larger area not fully depleted (i.e. very inefficient)

15. Jornadas LIP, Dez. 2005 15 P. Martins - CFTP-IST Hit maps from a bias voltage scan after 4 weeks Type inversion 40 V Pixels at small radii receive more fluence : Lowering the bias voltage leaves an ever larger area not fully depleted (i.e. very inefficient) Lowering the bias voltage leaves an ever larger area not fully depleted (i.e. very inefficient)

16. Jornadas LIP, Dez. 2005 16 P. Martins - CFTP-IST Hit maps from a bias voltage scan after 4 weeks Type inversion 30 V Pixels at small radii receive more fluence : Lowering the bias voltage leaves an ever larger area not fully depleted (i.e. very inefficient) Lowering the bias voltage leaves an ever larger area not fully depleted (i.e. very inefficient)

17. Jornadas LIP, Dez. 2005 17 P. Martins - CFTP-IST Physics from the Indium run Very good mass resolution ω and ϕ perfectly resolved ω and ϕ perfectly resolved η →µ + µ - seen for the first time in nuclear collisions η →µ + µ - seen for the first time in nuclear collisions Ability to trace muon offsets Prompt dimuons (resonances) peak at low values Displaced D meson decays have a long tail Weighted offset Data Prompt + Charm

18. Jornadas LIP, Dez. 2005 18 P. Martins - CFTP-IST Measure  c production in  c → J/ψ  +  decays High luminosity Radiation damagePile-up rejection Operate the vertex telescope at negative temperatures Fluences similar to the 2003 Indium run More accurate timing Challenges in proton-nucleus running 40 MHz average* interaction rate Lower leakage current and depletion voltages * Poisson statistics : 26 % of the time there are >1 interactions in 25ns Measure single muon production time differences Use silicon micro-strips at the start of the telescope Thin detector Minimizes electrons’ multiple scattering and energy loss Reduced material budget (no readout chips, hybrids or cooling rings on the way of the particles) Challenges met by… Use ATLAS silicon pixel detectors Measure peaking time in micro-strips   → e + e - measurement

19. Jornadas LIP, Dez. 2005 19 P. Martins - CFTP-IST 50 ns readout gate (4x shorter than the ALICE pixel planes) From idea to running experiment in 8 months Two planes fully cover the angular acceptance From all charged tracks… …we only keep those with a hit in the ATLAS planes Bad chips outside of acceptance ATLAS pixel planes

20. Jornadas LIP, Dez. 2005 20 P. Martins - CFTP-IST Reconstructed pulse shape Analogue pulse shape reconstruction provides timing and amplitude. Measured the phase between the 40 MHz clock and the (random) trigger arrival time. Dispersion of the reconstructed peaking time at low intensity Hits in time with trigger Hits from pile-up interactions Low intensity Nominal intensity Silicon micro-strip timing

21. Jornadas LIP, Dez. 2005 21 P. Martins - CFTP-IST 7 nuclear targets at two proton beam energies: 400 and 158 GeV Collected ~ 300’000 J/ψ events in p-A collisions at 400 GeV At 158 GeV we should be able to determine α(J/ψ) with an error better than 1% p-A @ 158 GeV ~ 30’000 J/ψ events 3 days’ data (before muon track matching) 2004 proton-nucleus run z-vertex (cm) Al U W Cu In 3 x BePb Beam of ~ 4 × 10 9 p/burst p beam 158 GeV

22. Jornadas LIP, Dez. 2005 22 P. Martins - CFTP-IST Summary and conclusions NA60 built and operated in 2003 the first radiation-tolerant silicon pixel detector in the world NA60 built and operated in 2003 the first radiation-tolerant silicon pixel detector in the world Unprecedented precision measurements in heavy-ion collisions Unprecedented precision measurements in heavy-ion collisions Very big impact in many physics topics in dimuon production Very big impact in many physics topics in dimuon production Integrated radiation doses comparable to years of LHC operation Integrated radiation doses comparable to years of LHC operation Detector still operational and even used in the following year Detector still operational and even used in the following year In 2004 we further upgraded this telescope with faster detectors In 2004 we further upgraded this telescope with faster detectors Successfully operated at interaction rates in excess of the LHC Successfully operated at interaction rates in excess of the LHC Questions? Merry Christmas and Happy New Year