P O Box 516, SE-751 20 Uppsala, Sweden
Researchers at the Department of Nuclear and Particle Physics at Uppsala University take part in the construction of the ATLAS experiment at the Large Hadron Collider (LHC) at the European particle physics laboratory CERN in Geneva. Activities in several fields of this experiment are described below.
Detector module development, metrology and electrical performance
Contact persons: Richard Brenner, Tord Ekelöf
The Uppsala group is together with the ATLAS groups in Oslo and Bergen producing Silicon Detector Modules for the innermost barrel of the SemiConductor Tracker. In total, around 400 Silicon Detector Modules will be produced. The silicon sensors is to be subject to quality control in Bergen before being assembled into Silicon Detector Modules in Oslo. The mechanical survey of the detector modules is done in Uppsala.
Electronic read out circuitry is mounted
on the
silicon sensor assembly in Uppsala, where the completed module is wire
bonded as well. One Silicon Detector Module will have around 10'000
wire bonds. An extensive Quality Assurance program is performed in all
three production sites. Results from electrical
performance and mechanical
precision of prototype and pre-series modules can be found
from these links.
The Uppsala group is also involved in irradiation
and beam
tests
of detector module prototypes at CERN. The aim of irradiation program
is to assure the functionality of front-end electronics, silicon
sensors and complete modules during the full life time of ATLAS. The
beam test verifies the performance of the detector modules in a charged
particle beam, and gives input to the parameterization of the detector
response.
Control and Monitoring
Contact persons: Nils Bingefors, Richard Brenner
The Uppsala group is developing control and monitoring for the SemiConductor Tracker (SCT) in ATLAS. The SCT is placed in a region with very high levels of radiation. The group work on developing a scheme to reduce the number of wires to readout the large number of temperature sensors inside the SCT.
The group is studying temperature, humidity and pressure measurements in high radiation environment up to 0.1 MGy (10 Mrad) and fluence of 2 * 1014 n/cm2. Test results on various developments and radiation can be found here. Archived material on old and completed development can be found here here .
Uppsala is presently coordinating the work on the Detector Control System (DCS) for the SCT. The work is done closely together with the ATLAS DCS group and in collaboration with Moscow State University. An overview of DCS interlock system components can be found here.
Charged Higgs physics
Contact persons: Tord Ekelöf
Most extensions of the Standard Model of particle physics
predict the existence of a pair of charged Higgs bosons H+
and H-. Their study depends on their mass, which
can be either below or above the top quark mass.
In the low mass case (mH<mt),
relevant both for ATLAS and D0, the charged Higgs boson is produced in
the t->bH +
decay. In most of the parameter space the charged Higgs boson decays
then further to tau nu. Making use of the tau polarization, we
reconstruct the Higgs mass and study the achievable mass resolution.
(link: Results)
In the high mass case (mH>mt),
relevant for
ATLAS, the charged Higgs boson is produced in association with a top
quark through b gluon fusion. It decays preferably to a pair of heavy
quarks: H+-> t .
The existence
of three b quarks in the event, two originating from the top quarks and
one from the Higgs decay, has been utilized in the search for this
event topology. Whether it is feasible to also require the detection of
the fourth spectator b-quark in the event and thereby improving the
potential of this search channel is the topic of a recently started
study.
External links:
- ATLAS SemiConductor Tracker (SCT)
- ATLAS at UiO
- Fysisk institutt Universitetet i Bergen
- ATLAS home page at CERN.
- Solid State Detector Development group home page at CERN
- Uppsala University The Svedberg Laboratory home page.
- The Ångström lab home page, Polacksbacken home page.
- Partikelfysik-Webuppgift home page.