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SiD02 Beam Calorimeter Studies

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Edward Estrada

Kevin Fiedler (graduate student at CalTech)

Alec Jenkins

Gleb Oleinik (graduated from CU)

Uriel Nauenberg

University of Colorado - Boulder 2011

University of Colorado - Boulder 2011

CMSSM Parameter Points Analyzed

• Studies focused on WMAP points at which there is a small difference between the and masses.

• M. Battaglia, A. De Roeck, J. Ellis, F. Gianotti , K.A. Olive, and L. Pape, Updated Post-WMAP Benchmarks for Supersymmetry.

University of Colorado - Boulder 2011

- Data are generated with:e- polarization = .8 and e+ polarization = -.3

University of Colorado - Boulder 2011

- Data are generated with:e- polarization = .8 and e+ polarization = -.3
- For some Standard Model processes, such as W pair production, a positron polarization of .3 or higher gives a higher signal to background cross section ratio.
- The two-photon cross section is about 1 million times that of the .

University of Colorado - Boulder 2011

Two-Photon Process

• Events in which the initial e- and e+ are undetected are made of low energy particles and possibly have high transverse momentum– the common features of most SUSY events.

University of Colorado - Boulder 2011

Beam Calorimeter Electron Detection Efficiency

• Oleinik’s efficiency study uses the coordinate system shown above.

• A clustering algorithm is used to separate energy deposits in the BeamCal due to electrons from those due to beamstrahlung.

University of Colorado - Boulder 2011

Cylindrical Cut

• The expected beamstrahlung deposit per tile is first subtracted, leaving candidate electron shower axes.

• A cylindrical cut is made by discarding tiles outside the approximate Moliere radius of each axis (5mm).

University of Colorado - Boulder 2011

Depth Cut

• Energy peaks of electron deposits are typically deeper than peaks due to beamstrahlung.

• A depth cut is made, discarding tiles 30mm from the surface of the BeamCal.

University of Colorado - Boulder 2011

• The average beamstrahlung deposit for each cluster axis is subtracted.

University of Colorado - Boulder 2011

• The efficiency of electron detection is calculated for various points in the BeamCal and an efficiency table is made by interpolating between these points.

University of Colorado - Boulder 2011

Signal Analysis of the

Major Cuts:

- All events are removed in which electrons or muons are detected (this includes those detected by the BeamCal).
- The event must have exactly two jets, each with either one or three charged particles.
- The acoplanarity of the two jets must be less than 2.2 radians (≈126°).
- The visible energy in the event must be less than 30 GeV.
- The combined transverse momentum of the event must be greater than 7 GeV/c.

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High Energy Electron Events Removed by the BeamCal and Main Detector

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BeamCal Comparison at the CMSSM point C’

= 9.6 GeV

m0 = 85, m1/2 = 400, tan(beta) = 10, A0 = 0, sign(mu) = +

University of Colorado - Boulder 2011

BeamCal Comparison at the CMSSM point D’

= 7.5 GeV

m0 = 110, m1/2 = 525, tan(beta) = 10, A0 = 0, sign(mu) = -

University of Colorado - Boulder 2011

Energy Cut Comparison at the CMSSM point B’

= 14.1 GeV

m0 = 60, m1/2 = 250, tan(beta) = 10, A0 = 0, sign(mu) = +

University of Colorado - Boulder 2011

Mass Measurement

• A spectrum fitting method is used to determine the masses of the and .

• SUSY data are generated at a range of parameter points, and a spectrum is made by comparing the new generated data to the original.

• Standard Model data are not regenerated for each point, and so subtraction of the background is complete. Because of this, the spectrum fit depends on the effect of the cuts on the SUSY data, not the visibility of the of the signal over the background.

University of Colorado - Boulder 2011

C'

m0

m1/2

tan(beta)

Measured Masses Input Masses

174 +1 -1 GeV 170.6 GeV

164 +.5 -.5 GeV 161.0 GeV

University of Colorado - Boulder 2011

Conclusions

• The signal can not be observed without the BeamCal in the region of parameter space where there is a low - mass difference.

• Although the spectrum fitting method does not depend on the visibility of the signal, those parameter points at which the signal is overwhelmed by the background are the same as those for which the spectrum fitting method does not lead to a unique set of parameters.

University of Colorado - Boulder 2011

References

D. Wagner, Introduction to Supersymmetry at the NLC, http://hep-www.colorado.edu/~nlc/SUSY_Wagner/susy/susynlc.html

S. Martin, A Supersymmetry Primer, arXiv:hep-ph/9709356, December 10, 2008.

M. Battaglia, A. De Roeck, J. Ellis, F. Gianotti , K.A. Olive, and L. Pape, Updated Post-WMAP Benchmarks for Supersymmetry, arXiv:hep-ph/0306219v1 June 23, 2003.

N. Arkani-Hamed, G.L. Kane, J. Thaler, and L.T. Wang, JHEP 0608, 070 (2006) [arXiv:hep-ph/0512190].

Uriel Nauenberg's Supersymmetry Group. http://hep-www.colorado.edu/SUSY/susynlc.html

K. Fiedler, G. Oleinik, U. Nauenberg, Electron Detection Efficiency of the SiD02 Beam Calorimeter for Various Beamstrahlung Intensities, December 12, 2010, http://hep-www.colorado.edu/~uriel/Beamstrahl_TwoPhoton-Process/effic3.ps

P. Bechtle, M. Berggren, J. List, P. Schade, and O. Stempel, Prospects for the study of the $\stau$-system in SPS1a' at the ILC, arXiv:0908.0876v1 [hep-ex], August 6, 2009.

PYTHIA. http://home.thep.lu.se/~torbjorn/Pythia.html

University of Colorado - Boulder 2011

References

W. Porod, Spheno, a program for calculating supersymmetric spectra, SUSY particle decays and SUSY particle production at e+ e- colliders, arXiv:hep-ph/0301101, February 1, 2008.

F.A. Berends, P.H. Daverveldt and R. Kleiss BDK. Monte Carlo simulation of two-photon processes. Comp. Phys. Commun., 1986.

K. Fiedler, Supersymmetric Signal Analysis and Mass Reconstruction of the Chargino (\chionep) at the International Linear Collider, March 9, 2011, http://hep-www.colorado.edu/SUSY/Fiedler_Chargino_Analysis.ps

C. Long, Undergraduate Honors Thesis, Advisor: U Nauenberg, Department of Physics, High Energy Physics Group, University of Colorado at Boulder, August 5, 2010.

C.F. Berger, J.S. Gainer, J.L. Hewett, B. Lillie, and T.G. Rizzo, General Features of Supersymmetric Signals at the ILC: Solving the LHC Inverse Problem, arXiv:0712.2965v2 [hep-ph], February 28, 2008.

A. Hahn, An Analysis of Selectron Masses Including the Effects of Beamstrahlung, August 16, 2004, http://hep-www.colorado.edu/SUSY/hahn_selectron.ps

ISASUGRA http://www.nhn.ou.edu/~isajet/

University of Colorado - Boulder 2011

Data Generation and Reconstruction

- Background data are generated using PYTHIA 6.4 and BDK:
PYTHIA - Z production, W production, Compton and Bhabha scattering

BDK - Two-photon process

•The SUSY spectrum is calculated using SPheno, and SUSY data are generated using PYTHIA 6.4.

•Data are reconstructed using MCFast from the org.lcsim framework, modified to include the BeamCal detection efficiencies.

University of Colorado - Boulder 2011

BeamCal Comparison at the CMSSM point G’

m0 = 115, m1/2 = 375, tan(beta) = 20, A0 = 0, sign(mu) = +

University of Colorado - Boulder 2011

Energy Cut Comparison at the CMSSM point SPS1a’

m0 = 70, m1/2 = 250, tan(beta) = 10, A0 = -300, sign(mu) = +

University of Colorado - Boulder 2011

BeamCal Comparison at the CMSSM point I’

m0 = 175, m1/2 = 350, tan(beta) = 35, A0 = 0, sign(mu) = +

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Mass Measurement

• Initial values are obtained by holding tan(beta) = 10, sign(mu) = +, A0 = 0, and then varying m0 and m1/2 over wide ranges.

• Precise measurements of the parameters are then made in the minimum m0 – m1/2 regions.

University of Colorado - Boulder 2011

Cut Comparison at the CMSSM point D’

m0 = 110, m1/2 = 525, tan(beta) = 10, A0 = 0, sign(mu) = -

University of Colorado - Boulder 2011