1 / 33

James L. Pinfold University of Alberta

Searching for the Magnetic Monopole and Other Highly Ionizing Particles at Accelerators Using NTDs. James L. Pinfold University of Alberta. The Discovery of the North Pole.

rane
Download Presentation

James L. Pinfold University of Alberta

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. Searching for the Magnetic Monopole and Other Highly Ionizing Particles at Accelerators Using NTDs James L. Pinfold University of Alberta 24th ICNTS Bologna

  2. The Discovery of the North Pole The idea that a magnet has two poles was thought up by a French mercenary Petrus Peregrinus during the siege of Lucera in 1269: “…in this stone you should thoroughly comprehend there are two points of which one is called the North, the remaining one the South.” Epistola de Magnete Petrus Peregrinus (1269) AhA! 24th ICNTS Bologna

  3. Symmetrizing Maxwell • Maxwell, in 1873, makes the connection between electricity & magnetism - the first Grand Unified Theory! Introducing a magnetic monopole makes the Maxwell’s equations symmetric • The symmetrized Maxwell’s equations are invariant under rotations in the plane of the electric and magnetic field • This symmetry is called Duality it means that the distinction between electric and magnetic charge is merely one of definition 24th ICNTS Bologna

  4. Dirac’s Monopole (1) • Paul Dirac in 1931 hypothesized that the magnetic Monopole exists • In his conception the Monopole was the end of an infinitely long infinitely thin solenoid • This was called the “Dirac String” • A depiction of this Dirac string (solenoid) can be seen opposite (c) 24th ICNTS Bologna

  5. Dirac’s Monopole (2) e- • Wouldn’t we see the Dirac string? • A particle with charge, say an electron, traveling around some path P in a region with zero magnetic field (B = 0 =  x A) must acquire a phase φ; given in SI units by: • The only way we would NOT see the Dirac string is if the wave function of the electron only acquired a “trivial phase” i.e.  = n2 (n =1,2,3..). That is, if: 24th ICNTS Bologna

  6. Dirac’s Monopole (3) • Hence Dirac’s quantization condition: • Where g is the “magnetic charge” and  is the fine structure constant 1/137. • This means that g=68.5e (when n=1)! • We can turn this around IF there is a magnetic monopole then: • If free quarks exist then the minimal electric charge is e/3…the minimal magnetic charge is then 3g Charge is quantized!! 24th ICNTS Bologna

  7. Monopole Properties Colour Charge Usually assumed to be 0 Monopole trajectory is “parabolic” in the r-Z plane of a solenoidal field and straight in the r- plane Electric charge =0. Magnetic Charge e=electron charge gD= ћc/2e =68.5e Dyon electric charge=1,2,3... Spin Usually taken as 0 or 1/2 Production at Accelerators usually assumed to be via Drell-Yan or Photon Fusion Monopole mass FREE PARAMETER See next slide Magnetic Charge e=quark charge =1/3 gD 3gD Energy loss By ionization (dE/dx)MM = 4700 (dE/dx)MIP See subsequent slides GUT monopoles can catalyse proton decay via the Rubakov-Callan Mechanism. Energy gain in a B-field: W= ngDBL = n20.5 keV/G.cm Coupling constant am= gD2/ћc =34.25 24th ICNTS Bologna

  8. Magnetic Monopole Energy Loss  > 10-2Ionization(à la Bethe-Bloch)(Zeeq)2= (gb)2 (a) for b = 1 : (dE/dx)MM = 4700 (dE/dx)m.i.p. 10-4<<10-2ExcitationMedium as Fermi gas(b) 10-4<<10-3Drell effect M + He  M + He* + Penning effect He*+ CH4 He + CH4 + e- (coupling of the atom magnetic moment with the MM magnetic charge)  < 10-4Elastic collisions(c) 24th ICNTS Bologna

  9. Track Etch Monopole Detectors • The passage of a highly ionizing particle through the plastic track-etch detector (eg CR39) is marked by an invisible damage zone along the trajectory. • The damage zone is revealed as a cone shaped etch-pit when the plastic detector is etched in a controlled manner using a hot sodium hydroxide solution. Look for aligned etch pits In multiple sheets 24th ICNTS Bologna

  10. Types of NTDs Commonly Used CR39 Rodyne/Makrofol UG-5 GLASS PLASTIC 24th ICNTS Bologna

  11. The Etching Procedure (to be used by MoEDAL - and used by SLIM) • Two etching conditions have been defined: • Strong etching: 8N KOH + 1.25% Ethyl alcohol 77°C 30 h • Soft etching: 6N NaOH+ 1% Ethyl alcohol 70°40 h • CR39 threshold: • “soft”etching Z/β~ 7 - REL ~ 50 MeV cm2g-1 • “strong”etching Z/β~ 14 - REL ~ 200 MeV cm2g-1 24th ICNTS Bologna

  12. Making Etching Better l A better signal to noise ratio 24th ICNTS Bologna

  13. A Typical Analysis Procedure (1) • A highly ionizing particle passes through the NTD leaving a microscopic trail • The latent track is manifested by etching • VB is the bulk rate • VT is the faster rate along the track • The reduced etch rate is p = VT/VB • The reduced etch rate is simply related to the restricted energy loss REL = (dE/dX)E<Emax 24th ICNTS Bologna

  14. A Typical Analysis Technique (2) a) • If the etching process is continued for a sufficient length of time a hole will be formed in the plastic (see (a)) • These hole can be detected by the “ammonia technique” (see (b)): • The plastic sheet is placed on top of blueprint paper • The two sheets are sealed along the edges • The package is exposed to ammonia vapour • Each hole in the plastic is revealed as a blue spot on the blueprint paper • This paper can then be used as a map for more careful etching of the corresponding region of the other NTDs in the stack b) Ammonia vapor NTD Blueprint paper 24th ICNTS Bologna

  15. Calibration 158 A GeV 207 Pb82+ Pbions +frag’s 5 < Z < 82 Reduced etch rate REL 24th ICNTS Bologna

  16. Seeking Monopoles at Accelerators • DIRECT Experiments - Poles produced and detected immediately & directly, searches with: • Scintillation counters & Wire chambers • Plastic NTDs • INDIRECT Experiments - in which monopoles are: • Produced, stopped and trapped in matter - (eg beam pipe) • Later they are extracted, accelerated & detected. 24th ICNTS Bologna

  17. Accelerator Based Searches 31 searches 14 using Plastic NTDs 3 using emulsions 3 using induction 11 using counters 24th ICNTS Bologna

  18. Why Use NTDs in Accelerator Searches for Monopoles • NTDs are sensitive to magnetic monopoles with n ≥ 1 and a broad range of velocities • It should be completely insensitive to normally ionizing particles (to the level of 1 part in 1016) • It is capable of accurately tracking monopoles and measuring their properties (Z/) • It doesn’t need high voltage, gas, readout or a trigger • The calibration of NTDs for highly ionizing particles is well understood • It is relatively radiation hard • It easily covers the solid angle in a very cost effective way *For Ldt =1040 cm-2 + rapidity interval of y = 2, there will be ~1016 MIPs thru the detector 24th ICNTS Bologna

  19. The 1st Accelerator Based Search for Monopoles Using NTDs (1) p-p Ecm ~50 GeV 24th ICNTS Bologna

  20. The 1st Accelerator Based Search for Monopoles Using NTDs (2) • 12 stacks of plastic deployed • Each stack consisted of 10 sheets: • 3 and 5th were Makrofole-E • The others were nitrocellulose 24th ICNTS Bologna

  21. The MODAL Experiment • The MODAL (at LEP) expt was run at √s = 91.1 GeV . The integrated luminosity 60+/-12 nb-1 • The detector used CR-39 plastic foils covering a 0.86 x 4π sr angle surrounding the I5 IP at LEP. • The polyhedral array was supported by a frame which was mounted on a fixed stand. The vacuum pipe was 0.5 mm al. • The 12 detector faces were filled with CR-39 with thicknesses (A) 720 μm, (B) 1500 μm, (C) 730 μm. • Detector response of all three plastic detectors were calibrated using heavy ions at LBL. Phy. Rev. D46, R881(1992) 24th ICNTS Bologna

  22. Direct Monopole Search at LEP (OPAL) monopole • The OPAL (LEP-1) monopole detector had a • Dedicated plastic detector element (LEXAN) • A dE/dX monopole trigger in the jet chamber • The OPAL search also employed the non-standard trajectory of the monopole in a solenoidal field • Search continued at LEP-2 using the jet chamber Anti-monopole Phys. Lett. B, 316, 407 (1993 24th ICNTS Bologna

  23. Monopole Search Limits 24th ICNTS Bologna

  24. The MoEDAL Experiment - the Monopole Search at the LHC • MOEDAL collaboration from: Canada (U of Alberta & U of Montreal); Italy (U of Bologna); CERN; Institute of Space Sciences, Romania. and, the USA (North Eastern University, Boston; U. of Cincinnati). LHCb MoEDAL 24th ICNTS Bologna

  25. The MoEDAL Detector MoEDAL NTDs • MoEDAL is an experiment dedicated to the search highly ionizing exotic particles at the LHC, using plastic track-etch detectors • MoEDAL will run with p-p collisions at a luminosity of 1032 cm-2 s-1 and in heavy-ion running • We can detect up to a 7 TeV mass monopole with charge up to ~3g • Due to make an initial deployment in 2009, with full deployment of detectors in 2010. LHCb VELO ~25 m2 area = 0 (layers) x 225 m2 =150 m2 of NTDs 24th ICNTS Bologna

  26. The MoEDAL Detector Element • 3 layers of Makrofol (each 500 mm thick) • 3 layers CR39 (each 500 mm thick) • 3 layers of Lexan (each 200 mm thick) • Sheet size 25 x 25 cm Aluminium face plate 25 x 25 cm 24th ICNTS Bologna

  27. The Next Step for NTDs at Accelerators • The LHC will start up in September 2008 • MoEDAL will submit its TDR for LHCC approval in the Fall of 2008 • Initial deployment of detectors in 2009 • Full deployment in 2010 • Plans for p-p and heavy-ion running MoEDAL 24th ICNTS Bologna

  28. Extra Slides 24th ICNTS Bologna

  29. Restricted Energy loss • Contribution to track formation is assumed to be only from the energy transferred by low energy delta rays with energies up to a threshold Eth • Threshold values range between 200 and 1000 eV 24th ICNTS Bologna

  30. Multi-Gamma Events • Multi- events • At the ISR pp  multi- at √s = 53 GeV,  < 2 x 10-37 cm2 • At FNAL (D0 Collab.) search for high ET-pairs in p-pbar collisions, Mmon. > 870 GeV/c2 for spin-1/2 Dirac MMs (95% CL) • At LEP (L3 Collab.) search for Z  Mmon > 510 GeV/c2 24th ICNTS Bologna

  31. 24th ICNTS Bologna

  32. 24th ICNTS Bologna

  33. The Definition of R 24th ICNTS Bologna

More Related