1 / 27

UPC in NA60

UPC in NA60. Jornadas LIP 2008 – Pedro Ramalhete. NA60 @ CERN. 8 MWPCs 4 trigger hodoscopes. hadron absorber. 17 m. toroidal magnet. vertex region. dipole magnet. hadron absorber. targets. 40 cm. Centrality of the In-In collision.

morrie
Download Presentation

UPC in NA60

An Image/Link below is provided (as is) to download presentation Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author. Content is provided to you AS IS for your information and personal use only. Download presentation by click this link. While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server. During download, if you can't get a presentation, the file might be deleted by the publisher.

E N D

Presentation Transcript

  1. UPC in NA60 Jornadas LIP 2008 – Pedro Ramalhete

  2. NA60 @ CERN 8 MWPCs 4 trigger hodoscopes hadron absorber 17 m toroidal magnet vertexregion dipole magnet hadron absorber targets 40 cm

  3. Centrality of the In-In collision Besides the muon spectrometer and the silicon pixel vertex tracker, NA60 had several other detectors which are very useful to have a clean tagging of the centrality of the In-In collision hadron absorber targetarea beam QBandZDC - Zero Degree Calorimeter (ZDC) on the beam line (just before the beam dump) - Quartz Blade (QB) on the beam line, just upstream of the ZDC - Beam Tracker (BT) on the beam line, upstream of the targets - Interaction Counter (IC) between the vertex tracker and the hadron absorber dipole field2.5 T targets beam hadronabsorber BeamTracker Vertex Tracker IC not to scale

  4. Ultra Peripheral Collisions

  5. Objective • Get the mass distribution of the VTdimuons produced in Ultra-Peripheral In-In Collisions • After accounting for backgrounds, acceptances and efficiencies, extract the absolute production cross sections of w, f and J/y photo-production, as well as their pT and rapidity distributions

  6. Possible ContributionsBeam ion remains intact • Beam ion remains intact • ZDC measures 115x158 = 18.17 TeV • Quartz Blade measures 49x49 = 2401 • Only Opposite-Sign muon pairs are created Beam Target

  7. Possible ContributionsBeam ion fragments • Beam ion fragments • ZDC measures 115x158 = 18.17 TeV • Quartz Blade measures less than 49x49 = 2401 • Only Opposite-Sign muon pairs are created Beam Target

  8. Possible ContributionsHadronic collision • Hadronic collision • ZDC measures less than 115x158 = 18.17 TeV • Quartz Blade measures less than 49x49 = 2401 • Opposite-Sign and Like-Sign muon pairs are created Beam

  9. What happens to the beam nucleus ? We are interested in considering two different cases within the UPCs: 1) In + In  In + In + m+m- 2) In + In  In* + In* + m+m- In the first case, the beam nucleus remains intact and the QB detector should see a signal corresponding to the square of the charge of the In nucleus: 492 In the second case, the beam nucleus fragments after the UPC and the QB sees a signal smaller than 492 (it sees the sum of Zi2, where Zi is the charge of fragment i) So, within the resolution of the QB detector, NA60 should be able to separate the UPC events in these two interesting sub-classes

  10. Event Selection

  11. Run, Burst and Event Selection • Run and Burst Selection • 2003 Indium-Indium data • Only the runs with 4000 A in the ACM toroidal magnet • NA60 standard run & burst selection for dimuon physics analyses • Event Selection • Both muons must be matched(from the Muon Spectrometer to the Vertex Tracker) • Both matched muons must belong to the same VT-Tracks vertex • The VT-Tracks vertex must be in target region([-4 : +4] cm, to exclude vacuum windows) • Only Dimuon T0J triggers(dimuon triggers stabilized in time by the Beam Tracker signals)

  12. Detectors used in Event Selection • ZDC (Zero Degree Calorimeter) • Measures the energy of the “beam spectator” nucleons • Is sensitive to Beam Pileup (and Interaction Pileup) • Readout gate of ~19 ns • Quartz Blade • Measures the (sum of squared) number of charges of the “beam spectators” • Is sensitive to Beam Pileup (and Interaction Pileup) • Readout gate of ~30 ns • Beam Tracker (or “beamscope”, BS) • Counts the beam ions and measures their time in relation to the trigger;it is also used to time-stabilize the dimuon trigger • Interaction Counter • Counts the interactions and measures their time in relation to the trigger • Is sensitive to Interaction Pileup • Vertex Tracker • Tracks charged particles and counts the number of interactions (Vertices) • Is sensitive to Interaction Pileup • Readout gate of ~200 ns

  13. VT-Dimuon Z-Vertex Distribution • The 7 Indium targets are easily recognized • Two peaks on the edges: windows of the vacuum box • Selection: -4.0 to +4.0 cm;keeps only dimuons produced in In-In collisions • Opposite-sign: m+m-Like-sign: m+m+ and m-m-

  14. The Zero Degree Calorimeter and the Quartz Blade detector

  15. Detector ResolutionZDC vs. Blade (beam triggers) Indium beam peak: EZDC = 115x158 = 18.17 TeV ; Blade = 49x49 = 2401 EZDC Blade

  16. Detector ResolutionProjection on the Blade axis • Projection on the Blade axis using EZDC in the interval [12 : 24] TeV • Peak at 2382 (49x49=2401) • Sigma = 216 (9%)

  17. Detector ResolutionProjection on the EZDC axis • Projection on the EZDC axis using Blade in the interval [1800 : 3000] • Peak at 18.59 TeV (18.17) • Sigma = 1.93 TeV (10%)

  18. Eliminating Beam PileupBeam Tracker Time Selection • Using only events with ZDC triggers we obtain the two plots (log scale for entries): • Left: ZDC vs Quartz Blade • Right ZDC vs Quartz Blade (with BeamScope time selection to eliminate beam pileup)

  19. Eliminating Beam Pileup 3DBeam Tracker Time Selection • Using only events with ZDC triggers we obtain the following 3D plots (linear scale): • Left: ZDC vs Quartz Blade • Right ZDC vs Quartz Blade (with BeamScope time selection to eliminate beam pileup)

  20. Beam Tracker Ion Timing • These figures show the ZDC vs. QB distributions for Dimuon triggers, before and after Beam Tracker Time Selection • This selection provides reliable measurements in the ZDC and Quartz Blade (with only very little remaining beam pileup) BT Time Selection

  21. Event SelectionZDC / Quartz Blade 2σ cut • In order to select ultra-peripheral events we use the ZDC and the Quartz Blade information and look for events with the following caracteristics: • The ZDC energy of a full ion: 115 nucleons x 158 GeV per nucleon = 18.17 TeV • The number of charges of a full ion: 49 protons;if there is no beam fragmentation, the Quartz Blade measures 492 = 2401 • We can use a 2D Gaussian to select events in a 2σ range around {18.17, 2401}, where σ is the resolution; this selection will reject 14% of good events • Given the resolutions of the ZDC and Quartz Blade detectors, the QB is better than the ZDC to distinguish “very peripheral collisions” from “no collisions at all” • The next slides show how the resolutions of the ZDC and QB were determined and how they are used in the Event Selection of this analysis

  22. Quartz Blade OS and LS (one track bins)BS + IC + 1 Vertex (Animated sequence) • Animated 2D sequence of the plots shown on the previous slides. • The elipse shows the area of the Blade/ZDC 2σ cut • Important things to notice: • Disappearance of the “peak” at 492for VTTracks>6 • Lowering of the mean ZDC value (Mean y) from 18TeV (2 tracks) to 16TeV (30 tracks) • Beam ion fragmentation increases with the number of tracks • After 15 tracks, almost no event is inside the Blade/ZDC cut

  23. End

  24. Backup Some slides with extra information

  25. hadron absorber The challenges muon trigger and tracking dipole field beam tracker vertex tracker iron wall magnetic field targets muon other • The vertex tracker has to handle very high charged-track multiplicities granularity  silicon pixels ! • And it has to survive a very high number of interactions (much higher interaction rate than trigger rate)  radiation hard detectors ! • And it should be as fast as possible, to reduce the interaction pile-up problem •  radiation hard silicon pixel detectors... operating at 10 MHz

  26. ironwall toroidalmagnet tracking chambers The muon spectrometer: some photos hadron absorber previously used byNA10, NA38 & NA50 beam added by NA60

  27. The NA60 target region in the 2003 Indium run 2.5 T dipole magnet Beam Tracker operated at 130 K(improves radiation hardness) Pixel detectors eight 4-chip and eight 8-chip planes

More Related