CU Group Work
Our group at CU has created a number of documents that describe
specifically the work we are doing:
- The work of David Wagner, who studied other ways of measuring the masses of supersymmetric particles:
You may also read the work of the students.
Our determination of the masses of
supersymmetric particles is based on two methods:
- 1)The methods presented by T. Tsukamoto, K. Fujii, H. Murayama,
M. Yamaguchi, Y. Okada, Phys. Rev D 51, 3153, 1995 which works well when
you can assume that the C.M. energy is well known. This implies that there are
no beam/bremmstrahlung effects degrading the beam energy.
- 2)A method initiated by us recently which takes into account the C.M.
energy degradation due to beam.bremmstrahlung.
- how to use
Root . A useful tutorial written by Deborah Weber and Rory Kelly.
- Calorimeter Resolution, as determined
by Mike Duckwitz using GEANT. Here he shows why the resolution varies
inversely as the square root of the energy.
- Cross sections
Similarly, as determined by Chris Takeuchi for either 80% right or 80% left
- We are now working on the simulation of the calorimeter design that we
have proposed for the Linear Collider Detectors. There have been two
papers that we are including here:
- The analysis by Gleb Oleinik to determine the separation of photon
at the calorimeter at a radius of about 1.7 meters in Z decays produced in
a 0.5 and 1.0 TeV e+e- collision Photon Separation
- Here we discuss the importance of the Beam-Cal in removing the
two-photon background that allows us to measure the stau mass in the
dynamical region over the WMAP constrained parameter space. In this region
the mass difference between the stau and the neutralino is small. In this
paper we use the Beam-Cal detection efficiency determined by Oleinik and
Fiedler to substantially reduce the two-photon background. This work is
carried out by Alec Jenkins and Kevin Fiedler named Signal Analysis of the Stau1 at the
- The study of the Chi-Square separation of single photons and two
photons from pi-zero decays done by Sarah Moll
- In 2003-2004 we began to study a different way to measure the masses
and parameters of the SUGRA SSSM model because the end point method does
not work well when beamstrahlung/bremmstrahlung effects are included in
the simulation. This new method and the reason for using it are discussed
in those papers below which include beamstrahlung/bremmstrahlung.
- Bradford Dobos has carried out an analysis including beam/bremmstrahlung
effects but also using positron polarization. It shows how powerful positron
polarization can be to separate the right and left smuon signals. The study of
this Smuon signal shows clearly the
deleterious effects of beam/bremmstrahlung and how one can use positron
polarization to unravel the energy spectrum of the muon from the left and right
- Jack Gill analyzed the sneutrino signal. It is interesting because the
mass value determination depends on the various parameters of MSUGRA.
Hence determining the sneutrino and slepton signals should provide a first
order determination of the parameters if MSUGRA is correct. His study
Sneutrino signal shows this aspect
- Jeremiah Goodson did a detail study, using the SPS4 parameters of the
Snowmass01 list, of the production and subsequent decay of the second
neutralino at a c.m. energy of 750 Gev. His paper
Study of the Second Neutralino describes very well why the end point
method does not work well when we include beamstrahlung in the process
and how much better our new method works.
- Andrew Hahn made also detail studies, using the SPS3 and SPS1 parameters,
of the selectron production when beamstrahlung effects are present. You can
read his write up Study of the Selectron Signal
and note that this new method gives much more accurate answers than the
energy end point method.
- We have found a novel way to measure the masses of the right and left
selectron using the energy end point method. This new way gives us resolutions
in the 0.1 GeV range. You can find our write up in New
Selectron Mass Determination or our Power Point presentation at the Chicago
- William Ruddick, in our group, discovered an error in the paper above.
The last equations showing the mass determination should have (-) signs.
The correct analysis is shown in Corrections
- We have a bunch of power point slides that discuss why we need good forward
tagging, has the plots describing our novel way of measuring selectron
masses, and another way to remove WW background. You may want to use them. They
- Mihai Dima's talk at the LCWS2000 meeting at Fermilab that reviews our
progress on selectron and smuon analysis is shown
- Starting in 2002 we have been working on studying how to observe the
signals using the SPS1 parameters generated in Snowmass 2001. These are high
tan(beta) (10) points which produce a lot of taus in the final state. We
have studied how to observe the second chargino and the higher neutralinos.
- The work of Anthony Johnson showing how well we can measure the masses of
the second chargino can be seen here.
- The work of David Staszak showing how well we can measure the masses of the
third and fourth neutralino can be seen here .
- The work of Tyler Dorland studying how to measure the mass of the second
neutralino can be seen here .
- Nick Danielson and Liz Goodman collaborated on a study of Point 2
selectron processes, and measured the masses of the selectrons and the
neutralino. This study concentrates particularly on the effects of
the two photon background:
- You can also look at the initial work of Nick Danielson on this subject
where there are some additional meaningful plots that describe the problem
of the two photon background:
- Rory Kelly and Chris Takeuchi collaborated on a study of the possible
effectiveness of a Cerenkov type counter to detect the high energy electrons
from a two photon process over the beamstrahlung-bremsstrahlung pair background
at angles around 30 mrad. They did this for a magnetic field of 6 Tesla:
- Jim Barron expanded this work to carry out the same analysis in a 4 Tesla
magnetic field and studied in greater detail the Cerenkov counter light output
difference between a two photon event and the beamstrahlung-bremmstrahlung
output in an area of 1 square centimeter:
- Kevin Fiedler has done an analysis to find the chargino in the case
of a parameter space where the chargino decays into a neutralino and W.
Chargino Analysis. He does the
analysis when the W decays into 2 jets.
- Liz Goodman's studies of selectron, smuon and Higgs boson
signals; these papers show how to make the
right cuts to enhance the supersymmetric signal by reducing the
Standard Model background.
- Brookie Williams' study of chargino signals; here the cuts and the
determination of the particle mass are more complicated: The Search for the Chargino
- James Barron studied the chargino signals including all sources of
background, namely the two photon background and Standard Model
background. He used some of the cuts developed by Brookie Williams but had
to go further to get rid of the additional sources of background:
The Search for the Chargino
- Nick Danielson's study of sneutrino signals; here the cuts are different,
but the determination of the particle mass is simpler:
The Search for the Sneutrino Or visit the short slide show version.
- Rory Kelly's study of the heavy neutralino production at Point 2 of the SUGRA
parameters: Heavy Neutralino at Point 2
Also available is an extremely brief summary in slideshow format of this work: Slide Show
- Deborah Weber's study of the heavy neutralino production at Point 1 of the SUGRA parameters:
Joseph Proulx's study of chargino production at Point 4 (non-SUGRA), "Study
of Point 4 Chargino Production and Observation of Low Energy Biases" is
available in a
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