September th ICNTS Bologna1 Searching for the Magnetic Monopole and Other Highly Ionizing Particles at Accelerators Using NTDs James L. Pinfold University of Alberta James L. Pinfold University of Alberta

September th ICNTS Bologna2 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!

September th ICNTS Bologna3 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

September th ICNTS Bologna4 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)

September th ICNTS Bologna5  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: Dirac’s Monopole (2) e-e-

September th ICNTS Bologna6 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!!

September th ICNTS Bologna7 Monopole Properties Magnetic Charge e=electron charge g D = ћc/2e =68.5e Magnetic Charge e=quark charge =1/3 g D  3g D g D  3g D Electric charge =0. Dyon electric charge=1,2,3... Coupling constant a m = g D 2 /ћc a m = g D 2 /ћc =34.25 =34.25 Energy gain in a B-field: W= ng D BL = n20.5 keV/G.cm Spin Spin Usually taken as 0 or 1/2 0 or 1/2 Monopole mass FREE PARAMETER See next slide Colour Charge Colour Charge Usually assumed to be 0 to be 0 Energy loss Energy loss By ionization By ionization (dE/dx) MM (dE/dx) MM = 4700 (dE/dx) MIP See subsequent slides See subsequent slides Monopole trajectory is “parabolic” in the r-Z plane of a solenoidal field and r-Z plane of a solenoidal field and straight in the r-  plane Production at Accelerators usually assumed to be via Drell-Yan or Photon Fusion GUT monopoles can catalyse proton decay via the Rubakov-Callan Mechanism.

September th ICNTS Bologna8 Magnetic Monopole Energy Loss <  <10 -2 Excitation Medium as Fermi gas (b) <  <10 -3 Drell effect M + He  M + He* + Penning effect He*+ CH 4  He + CH 4 + e - (coupling of the atom magnetic moment with the MM magnetic charge)  < Elastic collisions (c)  > Ionization (à la Bethe-Bloch) (Ze eq ) 2 = (gb) 2 (a) for b = 1 : (dE/dx) MM = 4700 (dE/dx) m.i.p.

September th ICNTS Bologna9 Track Etch Monopole Detectors Look for aligned etch pits In multiple sheets  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.

September th ICNTS Bologna10 Types of NTDs Commonly Used CR39 Rodyne/Makrofol UG-5 PLASTIC GLASS

September th ICNTS Bologna11 The Etching Procedure (to be used by MoEDAL - and used by SLIM)  Two etching conditions have been defined:  Strong etching: 8N KOH % 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 cm 2 g -1  “strong”etching Z/β~ 14 - REL ~ 200 MeV cm 2 g -1

September th ICNTS Bologna12 Making Etching Better l A better signal to noise ratio

September th ICNTS Bologna13 A Typical Analysis Procedure (1)  A highly ionizing particle passes through the NTD leaving a microscopic trail  The latent track is manifested by etching  V B is the bulk rate  V T is the faster rate along the track  The reduced etch rate is p = V T /V B  The reduced etch rate is simply related to the restricted energy loss REL = (dE/dX) E<Emax

September th ICNTS Bologna14 A Typical Analysis Technique (2)  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 a) b) Ammonia vapor NTD Blueprint paper

September th ICNTS Bologna15 Calibration 158 A GeV 207 Pb82+ Pbions +frag’s 5 < Z < 82 Reduced etch rate REL

September th ICNTS Bologna16 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.  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.

September th ICNTS Bologna17 Accelerator Based Searches 31 searches 14 using Plastic NTDs 3 using emulsions 3 using induction 11 using counters

September th ICNTS Bologna18 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 )  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 =10 40 cm -2 + rapidity interval of  y = 2, there will be ~10 16 MIPs thru the detector

September th ICNTS Bologna19 The 1st Accelerator Based Search for Monopoles Using NTDs (1) p-p E cm ~50 GeV

September th ICNTS Bologna20 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

September th ICNTS Bologna21 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)

September th ICNTS Bologna22 Direct Monopole Search at LEP (OPAL)  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 monopole Anti-monopole Phys. Lett. B, 316, 407 (1993

September th ICNTS Bologna23 Monopole Search Limits

September th ICNTS Bologna24 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). MoEDAL LHCb

September th ICNTS Bologna25 The MoEDAL Detector  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 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 LHCbVELO ~25 m 2 area = 0 (layers) x 225 m 2 =150 m 2 of NTDs MoEDAL NTDs

September th ICNTS Bologna26 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

September th ICNTS Bologna27 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

September th ICNTS Bologna28 Extra Slides

September th ICNTS Bologna29 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

September th ICNTS Bologna30 Multi-Gamma Events  Multi-  events  At the ISR pp  multi-  at √s = 53 GeV,  < 2 x cm 2  At FNAL (D0 Collab.) search for high E T  -pairs in p-pbar collisions, M mon. > 870 GeV/c 2 for spin-1/2 Dirac MMs (95% CL)  At LEP (L3 Collab.) search for Z   Mmon > 510 GeV/c2

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September th ICNTS Bologna33 The Definition of R