CE Wulz Institute of High Energy Physics 1 Institute of High Energy Physics of the Austrian Academy of Sciences New Physics at the LHC Experimental environment 2 ID: 656221
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Slide1
Claudia-Elisabeth Wulz
New Physics at the LHC
C.-E. Wulz (Institute of High Energy Physics)
1
Institute of High Energy Physics of the Austrian Academy of Sciences
New Physics at the LHCSlide2
Experimental environment
2
C.-E. Wulz (Institute of High Energy Physics)
Students will work within the CMS Collaboration.
Almost 20 fb-1 of integrated luminosity of pp interactions are available (√s
up to 8
TeV
), 300 fb
-1
are expected by 2021 (√s up to 14 TeV). Experience of Vienna CMS group: triggering, tracking, reconstruction of tracks and vertices as well as of muons, b’s and t’s.One thesis showcase is mainly about triggering, the other about searches for new physics in the field of SUSY. Connections between triggering and physics are an important aspect for both.
New Physics at the LHCSlide3
Motivation for New Physics
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The main motivation for the LHC, after the discovery of a Higgs boson, is the search for new physics.
The Standard Model, though extremely successful, leaves many questions open
.
It
needs to be embedded in an overarching theory, but which theory is it?
C.-E.
Wulz
(Institute of High Energy Physics) New Physics at the LHCConcrete predictions of experimental signatures for new physics exist for many models (SUSY, strong electroweak symmetry breaking, extra dimensions, etc.)Slide4
Scalar top quarks
4
C.-E.
Wulz
(Institute of High Energy Physics)
New Physics at the LHC
and are
expected to have large mixing, due to the large top Yukawa coupling.
The lower mass
eigenstate may be relatively light.Most analyses so far have exploited the decay channels or with as well as Slide5
Showcase 1 – Scalar tops decaying to charm
5
C.-E. Wulz (Institute of High Energy Physics)
Production of in association with two b-jets in the stop-
neutralino coannihilation region .
In this case the branching fraction is close to 100%.
Analysis strategies:
cut-based analysis
multivariate techniques as alternative background estimates from data where possible New Physics at the LHC
LO QCD
contributionLO electroweakcontribution
Signature: 2 b
-jets and missing energy, no leptonsBackgrounds:Slide6
Motivation for an Upgraded Trigger System
6
C.-E. Wulz (Institute of High Energy Physics)
New Physics at the LHC
Example for improvement in triggering on scalar tops
(e.g. through better
transverse momentum
estimates or pileup subtraction)
The current trigger system has worked very well. It is designed for luminosities up to 10
34 cm-2s-1, average number of pileup events of about 25, and a maximal Level-1 output rate of 100 kHz. For the future, the physics potential of CMS must be maintained or extended, and aging hardware must not become an issue. Luminosity, centre-of-mass energy and pileup will increase. Slide7
Showcase 2 – Muon trigger upgrade
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C.-E. Wulz (Institute of High Energy Physics)
New Physics at the LHC
Analysis
-
like, flexible
trigger algorithms already at Level-
1 with new
FPGA’s:e.g. boosted decision tree pT assignmentmore muon candidates than now, with higher precision in p
T
muon isolation information b-tagging of jet candidates through use of muon information.
Currrent
muon
trigger in the CMS cavernSlide8
Synergies within the DK and connections
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C.-E. Wulz (Institute of High Energy Physics)
Collaboration experiment – theoryA. Hoang (University of Vienna): QCD, SUSY
A. Rebhan (TU Vienna): QCD, SUSY
Theory groups (Institute of High Energy Physics): SUSY, QCD, new Dark Matter group (J.
Pradler
)
Development of trigger and reconstruction algorithms, data analysis in the fields of SUSY and other beyond the Standard Model physics
R. Frühwirth, M. Jeitler, J. Schieck (Institute of High Energy Physics)H. Abele (TU Vienna)ComputingAustrian Tier-2 GRID centreInternational CollaborationsCERN and institutions worldwide
New Physics at the LHCSlide9
Thank you for your attention!
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C.-E.
Wulz
(Institute of High Energy Physics)
New Physics at the LHCSlide10
BACKUP
10
C.-E.
Wulz
(Institute of High Energy Physics)
New Physics at the LHCSlide11
Added value
SUSY at the LHC
SUSY at the LHC
Students will work in a stimulating environment:
investigation of fundamental physics problems
world’s most powerful particle accelerator
large scientific community but human-sized research groups
international, multidisciplinary
Focus on research activities will shift to physics analyses, after long and important development work in triggering and tracking
Reinforcement of collaboration between theorists and experimentalists
C.-E.
Wulz
(Institute of High Energy Physics)
11
New Physics at the LHCSlide12
SUSY limits from CMS
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C.-E. Wulz (Institute of High Energy Physics)
New Physics at the LHCSlide13
ATLAS direct stop limits
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C.-E. Wulz (Institute of High Energy Physics)
New Physics at the LHCSlide14
ATLAS direct stop limits in 0-lepton channel
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C.-E. Wulz (Institute of High Energy Physics)
New Physics at the LHC
ATLAS-CONF-2013-024Slide15
Stop to charm
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C.-E. Wulz (Institute of High Energy Physics)
New Physics at the LHC
Alternative signature:
monojet
if Slide16
Projections for stop
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C.-E. Wulz (Institute of High Energy Physics)
New Physics at the LHCSlide17
CMS Trigger upgrade
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C.-E. Wulz (Institute of High Energy Physics)
New Physics at the LHCSlide18
Tail clipping
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C.-E. Wulz (Institute of High Energy Physics)
New Physics at the LHC
The initial pT estimate of about 32 GeV is too large
for the input
D
f
(ME1-ME2) value (50
f-units) according to the 5% tail fraction curve(shown in black). The initial 32 GeV estimate is substituted by the highest pT for which50 f-units is below the 5% tail fraction curve, in this case 12 GeV.