1. science
2. physics

Introduction to Dijet Resonance
Search at 13 TeV
Robert M. Harris
Fermilab
On Behalf of the Dijet Team
September 29, 2014
Outline

Motivation

Publication History & 13 TeV Expectations

Dijet HPA and Extensions

People and Meetings

Conclusions
2
Motivation

Search: Dijet Resonances
q, q, g
q, q, g
X
q, q, g
q, q, g

Powerful: LHC in run 2 is a dijet resonance factory at a new energy scale

Broad: search for many sources of new physics in a single simple search






String resonances from string theory
Excited quarks from theories of quark compositeness
W’, Z’ and scalar diquarks from grand unified theory
Gravitons from the Randall-Sundrum model of extra dimensions
Axigluons, Colorons and Color Octet Scalars from other new models
Model Independent: Publish cross section limits that can constrain any
present or future model of narrow qq, qg, or gg resonances.
Robert Harris, Fermilab
3
Publication History of Search at CMS

This exciting analysis has been published frequently by CMS,
often very early in the run, and the papers are highly cited

1.
2.
3.
4.
5.
Early publications at new energies get more citations.
3 pb-1 @ 7 TeV: Search for Dijet Resonances in 7 TeV pp Collisions at
CMS, Phys.Rev.Lett.105 (2010) 211801, 126 citations.
1 fb-1 @ 7 TeV: Search for Resonances in the Dijet Mass Spectrum from
7 TeV pp Collisions at CMS, Phys.Lett. B704 (2011) 123-142, 138 cites.
5 fb-1 @ 7 TeV: Search for narrow resonances and quantum black holes
in inclusive and b-tagged dijet mass spectra from pp collisions at sqrt(s) =
7 TeV, JHEP 01 (2013) 013, 36 citations
4 fb-1 @ 8 TeV: Search for narrow resonances using the dijet mass
spectrum in pp collisions at sqrt(s) = 8 TeV, Phys. Rev. D 87 (2013)
114015, 62 citations
20 fb-1 @ 8 TeV: publication draft with ARC, public PAS EXO-12-059.
4
Expectations @ 13 TeV

With 1 fb-1 expected from the first 3 week run in May or June
2015 the mass limit on q* would be 4.6 TeV


With 100 pb-1, ~2 days data, we reach current CMS limit of 3.5 TeV !
Approve analysis in summer 2015 !
2015 Schedule from T. Camporesi on 6/23/14
A. Weiler
6/23/14
5
Example of analysis from draft paper

Search of spectrum and limits on narrow resonances


Background modeled with same parameterization in all five papers.
Signals modeled with q* (qg) and RSG samples (qq and gg).
6
General Issues for Dijet HPA

Dijet resonance search is sensitive to new physics right away


The analysis needs to be ready to run on first data samples


Within days of running at 13 TeV we are exploring new territory !
Weekly check of dijet mass plot, background fit, and (data – fit)/error
Need to be organized and keep the HPA analysis simple

Following as much as possible the understood 8 TeV analysis steps


See presentation by Francesco Santanastasio with assigned tasks
Challenge may be understanding jet object and trigger rapidly

Close coordination with JetMET in understanding JEC and jet object


See presentations to follow by Mikko Voutilainen and Niki Saoulidou
Understand the trigger efficiency turn-on for trigger (HT, PFHT, …)

See presentation by Maxime Gouzevitch
Robert Harris, Fermilab
7
Related Non-HPA Analyses

These benefit from understood and approved HPA dijet resonance search

Reuse the baseline analysis technique and adds a new feature for a little more
sensitivity or a broader interpretation of the data.

Tagged Dijet Resonance Searches
 b, W / Z, H and q/g jet tagging (see presentation by Sertac Ozturk)

Additional Categories of Limits


Spin sensitive searches


Simultaneous searches in dijet mass and angle (bins of Dh or cos q*)
Extending the search to lower mass resonances


Wide dijet resonance shapes and Quantum black hole shapes
Using data scouting datasets or pre-scaled triggers at lower dijet mass
All interesting, but none are needed for the first HPA result.

Recommend limiting the scope to keep the HPA simple and fast
Robert Harris, Fermilab
8
People So Far

People from 8 TeV search
interested in 13 TeV search













John Paul Chou
Dinko Ferencek
Maxime Gouzevitch
Emine Gurpinar (student)
Robert Harris
Andreas Hinzmann
Bora Isildak
Shuichi Kunori
Sung-Won Lee
Sertac Ozturk
Maurizio Pierini
Francesco Santanastasio
New people interested in 13 TeV
search












Ayse Bat (student)
Christopher Cowden
M. Diamantopoulo (student)
Giulia Dimperio (student)
Kostas Kousouris
Georgios Mavromanolakis
Juska Pekkanen (student)
E. Sagkrioti (student)
Nikki Saoulidou
Erini Tziaferi
Mikko Voutilainen
An experienced group with
multiple students
9
Meetings so far

June 26


September 12


Discussed root tree maker and this mini-workshop
September 26


First organizing meeting during CMS Week
Discussed assignment of tasks
We will continue to meet at least bi-weekly on Fridays from 16-17:00
Robert Harris, Fermilab
10
Conclusions

We plan to search for narrow dijet resonances in run 2.

Analysis is mature, with five publications expected from run 1

We have assembled a team and begun to assign tasks


We could discover new physics with 1 fb-1 of run 2 data.


An experienced team including multiple new Ph.D students
We are as sensitive as run 1 with about 100 pb-1 of run 2 data
We plan for an approved result for summer 2015 conferences
Robert Harris, Fermilab
11
Backup
Robert Harris, Fermilab
12
Dijet Resonance Ph.D Theses
1. Kazim Gumus (2008) - preparation
CERN-THESIS-2008-066
https://cds.cern.ch/record/1121435
2. Sertac Ozturk (2011) - 7 TeV (~3/pb)
CERN-THESIS-2011-007
https://cds.cern.ch/record/1340571
3. Chiyoung Jeong (2011) - 7 TeV (~1/fb)
CERN-THESIS-2011-267
https://cds.cern.ch/record/1462016
4. Emine Gurpinar (2014?) - 8 TeV (~19/fb)
TBC
Robert Harris, Fermilab
13
Additional Reading
“Searches for Dijet Resonance at Hadron Colliders”
R. Harris and K. Kousouris
Int. J. Mod. Phys. A26 (2011) 5005-5055
arXiv:1110.5302
Robert Harris, Fermilab
14