Physics at a photon collider Page: 1 of 3
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FERMILAB-Conf-02/229-E September 2002
Physics at a Photon Collider
a Fermi National Accelerator Laboratory, P.O. Box 500, Batavia, USA
A Photon Collider will provide unique opportunities to study the SM Higgs boson and to determine its proper-
ties. MSSM Higgs bosons can be discovered at the Photon Collider for scenarios where they might escape detection
at the LHC. As an example for the many other physics topics which can be studied at a Photon Collider, recent
results on Non-Commutative Field Theories are also discussed.
only valid in LO, a realistic background simula-
tion should be based on a next-to-leading (NLO)
Several analyses of H - bb decays for a SM
Higgs boson in the mass range from 120 GeV to
160 GeV have been performed [3,4]. All analyses
exploit the kinematic differences between the s-
channel signal and the t-channel background by
cutting on visible energy and angular distribu-
tions. The results are shown in Fig. 1.
S100 12co tructedin ariantn (sGe)
The Photon Collider option of a Linear Collider
(LC) is based on laser photon back-scattering on
high energy electrons. The maximum photon en-
ergy is 205 GeV for a laser with A = 1.06pm
and an electron beam energy of 250 GeV. A high
degree of polarisation with opposite helicities of
the electron and the laser photon is crucial for
obtaining a peaked spectrum of high energy po-
larised photons close to the maximum energy. In
this case the high energy part of the yy spectrum
is dominated by the spin-0 configuration which
is important to enhance the signal and suppress
the background for Higgs production. Alterna-
tively, ey interactions are also possible. The tech-
nical aspects of the photon collider are discussed
2. Higgs Production
Neutral Higgs bosons are produced in the scat-
tering of two photons as a s-channel resonance
through a loop. In this loop all charged par-
ticles contribute which obtain their mass from
electroweak symmetry breaking. The two-photon
partial width of the Higgs boson is therefore sen-
sitive to physics beyond the SM.
For Higgs bosons decaying predominantly into
bb, the main source of background are 'y - QQ
processes (Q=c,b). The spin-0 component of
these processes is suppressed in Leading Order
(LO) by a factor m /s. Since this suppression is
*Talk given at SUSY2002 and ICHEP02
Figure 1. Reconstructed invariant mass for a
Higgs boson mass of 120 GeV with the full NLO
background simulation. The detector response is
simulated with SIMDET. Left plot from  and
right plot from .
Before b-tagging the ratio of background from
yy - cc events to yy - bb events is approxi-
mately 16 due to the quark charges. Excellent
S=120GeV L(O.65<z z j=3fb
W Higgs signal
EJts >O.6 -
- - e20 - N eg ud
-- q 1
F Bk round
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Soldner-Rembold, Stefan. Physics at a photon collider, article, September 30, 2002; Batavia, Illinois. (digital.library.unt.edu/ark:/67531/metadc742520/m1/1/: accessed December 10, 2018), University of North Texas Libraries, Digital Library, digital.library.unt.edu; crediting UNT Libraries Government Documents Department.