Search for Supersymmetry with early LHC data David Stuart, UC, Santa Barbara. May 12, 2010

Search for Supersymmetry with early LHC dataDavid Stuart, UC, Santa Barbara. May 12, 2010

Outline

What is Supersymmetry & why are we looking for it?

How do we go about searching for it?

When might we find it?

The Standard Model, an incomplete success

Parameters unexplained: masses, mixings, couplings.

W, Z, fermion masses could be generated by Higgs

mechanism.

=> Search for Higgs at CMS

mechanism.

mechanism. But mass values still not explained.

And mH should diverge due to corrections:

mechanism. Though values not explained.

And mH should diverge due to corrections.

Would cancel if fermionboson “super symmetry”.

mechanism. Though values not explained.

And mH should diverge due to corrections.

Would cancel if fermionboson “super symmetry”.

Cancel the debt by printing more particles.~

Unification would be nice.

Unification would be nice, and corrections from the extra “SUSY” particles seem to provide it.

The standard model does not explain dark matter.

A conserved SUSY quantum number would. The LSP.

Supersymmetry, an experimentalists dream

Many parameters to measure. Doubled mass spectrum, more mixings.

New puzzles to solve. Whence the masses and mixings?

Why is the symmetry broken?

Supersymmetry, an experimentalists dream

Many parameters to measure. Doubled mass spectrum, more mixings.

New puzzles to solve. Whence the masses and mixings?

Why is the symmetry broken?

Supersymmetry’s variety of signatures makes it

a target representative of many new models.

How to search for SUSY?

Produce super-partners, and

detect that we have done so.

Massive, so need energy => LHC

Production via SM like diagrams.

For example...

The same diagram that produces WZ in SM…

…could produce Winos and Zinos.

The cross section for weak production is small.

But squarks & gluinos would be strongly produced…

In pairs if RP conserving.

Cross-section is calculable given masses.

Example: 400 GeV squark and gluino

gives ≈40 pb at 7 TeV.

≈ 1/4 of top quark cross-section.

Could produce thousands this year.

Varied signatures

Higgssector

squarks

gluino

sleptons

charginos/neutralinos

A CMS mSUGRA benchmark, LM0

Higgssector

squarks

gluino

sleptons

Varied signatures

Higgssector

squarks

gluino

sleptons

Varied signatures

Many different search modes

Multijets + MET

Lepton + jets + MET

Dileptons + jets + MET

Same sign dileptons + jets + MET

Trileptons + jets + MET

Many different search modes

Each mode has different backgrounds.

Search amounts to predicting these bkgdsand looking for an excess above prediction.

Multijets + MET Lepton + jets + MET

Dileptons + jets + MET Same sign dileptons + jets + MET

Trileptons + jets + MET

Background cross-sections

Need to predict the Njet and MET tails?

But kinematic tails are hard to calculate:higher orders, pdfs, detector effects…

e.g., Z+jets

How to predict the Njet and MET tails?

Monte Carlo predictions?

Sophisticated, higher order modeling,

e.g., ALPGEN.

Elaborate simulation of detector response.

Monte Carlo predictions?

Sophisticated, higher order modeling,

e.g., ALPGEN.

Elaborate simulation of detector response.

Both are software…Only trust in so far as validated with data.

Data validation challenges:

Fit away signal?

Data validation challenges:

Fit away signal?

Don’t want to wait…

Would like a quick, data-driven method to predict MET in Z+jet events.

In this case it is fake MET,

from mis-measurement.

Missing ET in Z+jets

The Z is well measured. The MET comes from the detector’s response to the jet system.

For each Z+jet event, find an event w/ a comparable jet system and use its MET as a prediction.

Huge QCD x-section makes such events SUSY free.

For each Z+jet event, use a MET template measured from events with a comparable jet system in O(1) pb-1.

Templates measured in bins of NJ and JT = j ET.

Missing ET in Z+jetsExample of template parameterization

Background predictionData distribution

For each data event...

Missing ET in Z+jetsExample of template parameterization

Background predictionData distribution

For each data event,look up the appropriate template.Sum these, each withunit normalization, to get the fullbackground prediction

N JETSpT>50 GeV

sumETBin 1

sumET Bin 2

sumETBin 3

sumET Bin 4…

Missing ET in Z+jets, MC closure test

Missing ET in Z+jets, MC closure tests

“Scaled” includes a low MET normalization, which is important for low NJ.

Missing ET in +jets, MC closure test

Missing ET in +jets, MC closure tests

“Scaled” includes a low MET normalization, which is important for low NJ.

Missing ET in Z/+jets, robustness tests

Various detectoreffects could addMET tails.

Check robustnesswith MC tests,applied equally toall samples.

• R=0.8 hole at (h,f)=(0,0)• Double gaussian smearing• Randomly add 50-100 GeV “noise jets”• Vary nJ slope by ±50%.• Jet energy scale sensitivity.

Now working to validate this with low ET +jets from early data.

Missing ET in W()+jetsW

Can we predict W+jets, and ttW+jets?

Missing ET in W()+jets

Templates can predict the fake MET in W+jet events, but we also need to predict the real MET, i.e., the pT.

Missing ET in W(+jets

Templates can predict the fake MET in W+jet events, but we also need to predict the real MET, i.e., the pT.

But, the pT spectrum is ≈ same as the pT spectrum,

if we ignore V-A or randomize W polarization.

Missing ET in +jets

Pretend we could detect and apply templates.

Mismatch due to b-jet dominance.

But, neutrino pT dominates MET.

Missing ET in +jets

Combining template prediction with pT spectrum

gives a prediction for the full MET distribution.

Missing ET in +jets

The same approach predicts W shape,

if polarization is not extreme.

Comparison with signal

Benchmark points (LM4 and LM1) stand out with 200/pb at 14 TeV.LM4=(m0=210,m1/2=285); LM1=(60,250). tan()=10.

But we don’t have 14 TeV.

But we don’t have 14 TeV. So it will be a bit harder.

When will we discover SUSY with 7 TeV?

But we don’t have 14 TeV. So it will be a bit harder.

When will we constrain SUSY with 7 TeV?

Systematic uncertainty assumed to be 50% overall.Separate tight selections for 100 pb-1 and 1 fb-1.

Expected limits in multijets + MET search

When?Similar limits from same-sign dilepton search

When?So far, we only have a few inverse nanobarns. But, that is a few hundred million events…

Detector performance encouraging with first data.

Tracking calibrated with Ks, , ,J/, D resonances.

When?Expect 100 pb-1 by end of this year and 1 fb-1 by end of next year. Tuning up…

Summary

Potential for quick sensitivity to Supersymmetry

If we can obtain robust, data-driven background predictions

QCD based templating gives an in situ prediction of MET distribution.

Charged lepton pT predicts neutrino pT.

Acknowledgements

MET prediction method by Victor Pavlunin. PRD81:035005 arXiv:0906.5016

Several slides borrowed from Jeff Richman

Other material from

…and references therein.

Extra slides

Dileptons

m(e±m) m(l +l −)

%χ20 → l +%l −; %l − → l − %χ 1

Leading order cross section, tan = 3, A=0, >0

Rough limit from Tevatron

Typical decay patterns in LM0

%b1 → %t1W

−(43%)

%t1 → %χ1

+W−(100%

%b1 → %χ20b(29%)

→ %χ1−t(24%)

%χ20 → %χ 1

0e+e− (3.3%), %χ 10μ +μ − (3.3%)

Typical decay patterns in LM0

%g → %b1b + c.c.(54%)

%b1 → %t1W

−(43%)

%t1 → %χ1

+W−(100%

%g → %t1t + c.c.(46%)

Standard Model backgrounds to Z+jets

Search for Supersymmetry with early LHC data David Stuart, UC, Santa Barbara. May 12, 2010

Documents

LHC SUSY SPIN MEASUREMENTS SPIN PRAHA 2009 1 Spin Measurements in Supersymmetry at the LHC Christopher Lester Cavendish Laboratory, Cambridge (on behalf

Supersymmetry Report

Searching for Supersymmetry at the LHC and Elsewhere

Flavor-Symmetry based Flavor Violation in Supersymmetry Jisuke Kubo (kanazawa Univ.) at NCTS LHC Topical Program 1 based on: Babu and JK, PRD71, 056006

F. Zwirner- Why Supersymmetry and/or New Physics in the LHC Era?

LHC HIGGS BOSON IMPLICATIONS FOR SUPERSYMMETRY

Supersymmetry at LHC and beyond

Searches for long-lived particles in Hidden Valley scenarios with the Atlas detector at the LHC SUSY 2015, 23 rd International Conference on Supersymmetry

SuperSymmetry at the LHC and LHeC

Supersymmetry - physik.uni-graz.atphysik.uni-graz.at/~axm/susy2009.pdf• Supersymmetry and supergravity by J. Wess and J. Bagger (Princeton) ... • Supersymmetry, Supergravity and

Supersymmetry Searches and its implications Monoranjan Guchait TIFR, Mumbai From Strings to LHC III 8-14 th December, 2012 Puri

SUSY searches with the ATLAS detector200.145.112.249/webcast/files/SUSY_ATLAS_Ventura... · SUSY at the LHC •Supersymmetry is a favoured extension of the Standard Model (SM) •Postulates

Supersymmetry at the LHC - Heidelberg University · Supersymmetry at the LHC Georg Weiglein IPPP Durham Heidelberg, 08/2007 Introduction Properties of SUSY theories What is the scale

Supersymmetry - DAMTPon extended supersymmetry. •Aithchison, “Supersymmetry in particle physics”, Cambridge University Press is su-per clear and basic. •Martin “A supersymmetry

Desperately Seeking Supersymmetry [SUSY]vsharma/lhc/LHC-Physics-Talks/rabi-susy.pdfDesperately Seeking Supersymmetry [SUSY] 2 1. Introduction Supersymmetry is a space-time symmetry;

Split Supersymmetry: Signatures of Long-Lived Gluinos Intro to Split SUSY Long-Lived Gluinos @ LHC Long-Lived Gluinos in Cosmic Rays JLH, Lillie, Masip,

Searching for Supersymmetry with the ATLAS Detector at the LHC

Search for Supersymmetry Signals at the LHC

Constraints on Supersymmetry using the latest data from cosmology, DM searches and LHC

John Ellis King’s College London (& CERN) Supersymmetry, Higgs & LHC Physics What we (don’t) know What else is there? How to discover it?