2 The CDF Experiment at Fermilab Contents - Harvard University ...

72 Section 2: CDF Physics Analysis
2.4.3 Missing Transverse Energy + Jets
(Dr. Burkett & Ms. Spiropulu)
6E T +2jets. Harvard has garnered much expertise in the use of missing transverse energy
for particle searches (see earlier discussion of the 6E T +jets search with the Run I data).
Branching out from the squark and gluino searches, we see two new topologies of interest:
1. 6E T +two jets (optional b-tag)
2. 6E T + one jet { the so-called \monojet" topology.
The natural application of 6E T +2 jets would be to stop and sbottom searches. In the latter
case b-jets would be expected so a b-tag would help reduce the background tremendously. We
recognized that these events also are sensitive to higgs bosons, through the channel pp ! Zh
with Z ! and h ! bb. Triggers designed for supersymmetric particles by Spiropulu turn
out to have avery good acceptance for higgs, too. This is discussed further below.
6E T +1jet.
Superstring theories that provide a framework of unication of all forces can describe
a real multidimensional world having a size measured in the Planck scale unit, about R =
10 ,35 m. In the vacuum state, one time and three spatial dimensions expand to the size
we observe. Each resulting tower of particles includes a massless state and its excitations
(called Kaluza-Klein) whose masses are set by the size of the compact dimensions, which
would naturally be R ,1 =10 19 GeV. The Standard Model particles are the massless states
that acquire their small observed mass from the breaking of electroweak symmetry and
supersymmetry. But there is no compelling reason why all dimensions should be either the
size of the Planck scale or the size of the observed universe - it could happen that dimensions
of the order of the weak scale (TeV or mm) arise in determining the ground state. In such
a theory the quarks and leptons are to be identied with states that have no Kaluza-Klein
excitations while the gauge bosons have a tower of excitations of mass n=R where n is
the number and R is the size of the extra dimensions. The interactions of the excitations
with quarks, leptons and gauge bosons is xed by the theory. Recently Arkani-Hamed,
Dimopoulos and Dvali [20] and in the early 1990's Antoniadis et.al have argued that the
fundamental gravitational scale can be as low as TeV energies while the size of the extra
dimensions can be as large as a millimeter. In this case gravitons should be radiated at
signicant rates in high energy particle collisions.