A Direct Search for Magnetic

1

HEP03, Aachen, 17-23/7/03
A Direct Search for Magnetic Monopoles at H1
David Milstead The University of Liverpool
2
Monopoles in Particle Physics
Electric charge quantisation
Dirac - enh/gm0
Gauge group symmetry breaking
t hooft/Polyakov Monopole from breaking of
simple symmetry group into U(1)
SUSY GUTs 1015 GeV Little Higgs 1-5 TeV ?

3
Monopoles at HERA
First search in ep at 300 GeV Sensitive to
150 GeV mass QED coupling for Dirac Monopole
gD aggD2/4p 34 aem1/137
p
Processes predicted but not rate 103 greater
ionisation energy loss rate than mip
4
Monopoles in the H1 beam pipe
Monopoles of strength gt 0.75 gD stopped Bind to
Al nucleus dipole moment and only released by
melting (Milton et al.) Take 60cm section of 2mm
thick H1 beam-pipe around interaction zone. Used
1994-1997 lumi60pb-1 Cut into 14 strips
and pass through superconducting loops and
measure current.
5
Southampton SQUID

• DC SQUID (2G mod. 581) at Southampton
  Oceanography Centre, UK.
• Sample sizes up to 1m long and 5cm radius.
• Measures changes in magnetic field 10-12 T.

6
Calibration

• Signature of monopole is persistent current
• Use solenoids with varying currents to mimick step

x 10-2
90gD
Induced current
x 10-1
10gD
1.2gD
position /cm
7
Signal survival

• Monopole signal survives after strip traversal

strip
i
Solenoid ( 1 gd)
8
Beam pipe measurements

• Induced current from strips

Dirac Monopole
Current
Strip number
No candidates found
9
Monopole Acceptance
Use gg-gt mm (comphep) model
Rising acceptance with high charge and low mass
10
Cross-section upper limits
First upper limits in ep collisions
11
Upper limit for Dirac Monopole Production
Different experimental techniques Competitive ep
limit
12
Upper limit for 3gd monopoles
Only limits from ep and pp
13
Summary and Outlook
Magnetic monopoles play fundamental role in
modern physics theories.
First search in electron-proton scattering at
300 GeV at the H1 experiment Search for
monopoles stopped in the beam pipe. Monopole
masses up to 150 GeV and charges 1 lt gD lt 6
excluded.