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New Particle Searches in CMS
DongHee Kim
WCU High Energy Collider Physics Research
Kyungpook National University
KIAS Phenomenology Workshop
2011Nov16-19 KIAS Pheno. Workshop
“CERN changes the policy that not finding Higgs is the discovery” Larry Nodulman, CDF EWK convenor
at the CDF collaboration meeting and Tevatron End Beam (Sept 29-30 2011)
We may be in the era which is quite uncertain ! Let’s wait to understand the nature a little bit more by Human Being !
Higgs is the most intrigueing at the moment ! Higgs particle is not all needed to be discovered ! Some channels are under discovery mode by both CMS and ATLAS. Higgs, SUSY, Z’ and W’ etc… is being under search
2011Nov16-19 KIAS Pheno. Workshop
WE MAY KNOW THE RESULT THIS YEAR : ONE MONTH LEFT !
3 2011Nov16-19 KIAS Pheno. Workshop
New Physics at High Energies?
Extra Dimensions?
Black Holes???
Little Higgs?
ZZ/WW resonances?
Higgs ?
SUSY particles ?
We do not know what is out there for us… A large variety of possible signals. We have to be ready for that
New Gauge Bosons ?
Any others ??
?
2011Nov16-19 KIAS Pheno. Workshop
This year 2011, 5.20 fb-1 recorded ! 91% efficiency 550 pb-1 / week, L = 3.7 x 1033 cm-2 s-1 Typical fill : duration of 16.5 hours, 117
pb-1 delivered, 113 pb-1 recorded Now in the mode of publication
preparation of important channels
targeting at the end of Dec 2011 !
CMS Status & Contents
Higgs, Z’ & W’, ED and SUSY particle searches However, Results based on by LP conference Later results are not allowed yet for the presentation Lots interesting things going on since then lots preparations for pub.
Before x-mas Of particular, the watch mode may be under intriguing !
The results shown here based on at most ~2 fb-1 data !
Contents
CMS Status
Integrated Luminosity (2011 Run)
2011Nov16-19 KIAS Pheno. Workshop
Muon Chambers (Barrel: 250 DTs + 480 RPCs) (Endcaps: 473 CSCs + 432 RPCs)
Superconducting Solenoid (niobium-titanium coil) 3.8T
Forward Calorimeter (Steel + Quartz fibers) ~2000 channels
Hadronic Calorimeter (Brass and Plastic Scintillators) ~7000 channels
Electromagnetic Calorimeter (PbWO4 Scintillating Crystals) ~76K channels
Silicon Tracker (Pixels: 100 x 150 um2) (Microstrips: 80 – 180 um) millions of channels
Steel Return Yolk (~13000 tones)
PreShower (Silicon strips) ~137K channels
Detector, The CMS
Higgs ??
2011Nov16-19 KIAS Pheno. Workshop
As of March 2011, Open window : 114 < Mhiggs < 155 GeV and 183 ~ 185 GeV Excluded by Tevatron in the range 155 ~ 183 GeV recently Tevatron reach only to 200 GeV Since then, the search was extremely hectic to dig the Higgs out !!!
2011Nov16-19 KIAS Pheno. Workshop
Higgs Production in 7 TeV pp Collsions
gg H is dominant production mechanism
2011Nov16-19 KIAS Pheno. Workshop
SM Higgs Decay Modes vs Mass
[GeV]HM
100 200 300 400 500
BR
[pb
]´
s
-410
-310
-210
-110
1
10
LH
C H
IGG
S X
S W
G 2
011
SM = 7TeVs
ml = e, tn,mn,en = n
q = udscbbbn
± l®WH
bb-l
+ l®ZH
-t+t ®VBF H
-t+t ®H
gg
qqn±
l®WW
n-ln
+ l®WW
qq-l
+ l®ZZ
nn-l
+ l®ZZ
-l
+l
-l
+ l®ZZ
Mode Mass Range Data Used (fb-1) CMS Document
H γγ 110-150 1.7 HIG-11-021
H bb 110-135 1.1 HIG-11-012 (NEW)
H ττ 110-140 1.1 HIG-11-009
H WW 2l 2ν 110-600 1.5 HIG-11-014
H ZZ 4l 110-600 1.7 HIG-11-015
H ZZ 2l2τ 180-600 1.1 HIG-11-013 (NEW)
H ZZ 2l2j 226-600 1.6 HIG-11-017
H ZZ 2l2ν 250-600 1.5 HIG-11-016
Three distinct regions between 110 – 600 GeV
2011Nov16-19 KIAS Pheno. Workshop
Low Mass Higgs Search : H γγ
9
γ1= 86 GeV
γ2=56 GeV
Signature: 2 energetic, isolated γ, narrow mass peak
• Background shape fitted by 2nd order polynomial constrained to be positive
• Signal shape : Sum of 3 Gaussians, parameters determined from Z ee data
Simulated data not used in analysis
2011Nov16-19 KIAS Pheno. Workshop
Low Mass Higgs Search : H γγ
Unconverted γγ, both in ECAL
barrel
1 converted γ, both in ECAL barrel
1 converted γ, one in ECAL endcap
Unconverted γγ, one in ECAL endcap
CMS Prelim
Low Mass Higgs Search
H ττ channel
H bb channel
2011Nov16-19 KIAS Pheno. Workshop
Intermediate Mass Search 130 < MH<200 H WW 2l 2ν
2011Nov16-19 KIAS Pheno. Workshop
SM Higgs boson with mass 147 < MH < 194 GeV ruled
out at 95% CL.
SM Higgs boson expected sensitivity
136 < MH < 200 GeV
The Golden Channels H ZZ 4l
H ZZ 2l 2τ (NEW)
2011Nov16-19 KIAS Pheno. Workshop
e: 177 GeV
Jet: 207 GeV
e: 114 GeV
M2l2j = 580 GeV
Jet: 114 GeV
High Mass Higgs Search H ZZ 2l 2ν
H ZZ 2l 2q ( or 2b)
CMS Preliminary
2011Nov16-19 KIAS Pheno. Workshop
Summary Of All Searches : Expected & Observed
CMS Preliminary • Solid line =
Observed limit • Dashed line =
Expected
2011Nov16-19 KIAS Pheno. Workshop
SM Higgs Search Combination
• Expected exclusion mass range:
130 – 440 GeV
• Observed exclusion mass range: [145-216] [226-288]
and [310-400] GeV
2011Nov16-19 KIAS Pheno. Workshop
Excess in the low mass range(red circle) seems to persist but with less significance.
Now 3-5 times more data/channel analysis ongoing for all modes
2011Nov16-19 KIAS Pheno. Workshop
The Evolution of Higgs Search As of March 2011, 114 GeV < Mhiggs < 157 GeV and 183
GeV < Mhiggs < 185 GeV leftover
Direct measurement by Tevatron(157 ~ 173(95% C.L.) and 173~183 GeV(90% C.L.) excluded
As of Summer 2011, 114 GeV < Mhiggs < 145 GeV low mass
region) leftover
Exclusion extended to 400 GeV with very a little window of 261~226 GeV and 288 ~ 310 GeV
Modest excess Higgs mass below 145 GeV
Entire region will be searched by next year !
2011Nov16-19 KIAS Pheno. Workshop
Lepton decay core of discovery attempt !
CMS has very good ID capabilities in both electron and muon
Lepton related decay dilepton and lepton + MET etc…
New Heavy Gauge Bosons ?
Background almost free ! watch mode !
2011Nov16-19 KIAS Pheno. Workshop
The majority of extensions to the SM predict new gauge interactions, many of which naturally result in the prediction of neutral bosons, such as a highly massive Z’ particle
New neutral bosons from E(6), SO(10) , GUT and even SUSY since many models possess U(1) symmetry: Sequential Z’ (SM coupling), Zy, Zh, Zc,Zi in GUT E(6) Model
Z’ and W’ introduced from extra SU(2) symmetry: Left-Right extended SM etc..
Looking for resonances decaying to leptons provides very clean signature even in a hadron collider for the neutral gauge bosons.
Looking for lepton with MET for charged gauge bosons.
Dilepton selection
2011Nov16-19 KIAS Pheno. Workshop
Dielectron mass spectrum
2011Nov16-19 KIAS Pheno. Workshop
dimuon mass spectrum
2011Nov16-19 KIAS Pheno. Workshop
Resonance search
Simple signal + background pdf, with shape parameters from MC; fit explores the difference in shapes.
Use likelihood ratio to calculate uncorrected significance SL as a function
of the dimuon mass M. Correct for probability of getting at least
as extreme of a fluctuation from backgrounds
2011Nov16-19 KIAS Pheno. Workshop
Mass limit of Z’s
• Set limits on ratio of cross sections at 95% CL using a Bayesian method
2011Nov16-19 KIAS Pheno. Workshop
2011Nov16-19 KIAS Pheno. Workshop
Event Selection of W’
Event Selection
-. Highest ET/pT single lepton trigger (unprescaled)
-. Only One (good quality) isolated highest ET/pT lepton
(kinematic / isolation / shower shape in detector)
-. Lepton ET/pT and MET are similar in magnitude and back-to-back in transverse plane
(ratio of ET / deltaPhi)
Signal Selection Efficiencies
-. > 80% in both electron and muon channel
-. Fairly independent of W’ mass
Lepton + MET channel
2011Nov16-19 KIAS Pheno. Workshop
W’ → electron + MET signature
Spectacular signature -. One very high energetic electron (straight track)
-. “nothing else” in the event
Event with the highest MT = 922 GeV/c2
Mass Limit
2011Nov16-19 KIAS Pheno. Workshop
• 36pb-1 data published to PLB (also CDF W’ published) • Results with 1.1fb-1 by combining electron+muon
channels • New Limit set MW’ > 2.1 TeV at EPS(July 2011)
• Under preparation of next round (by Dec 2011) • Interference effect under study • apply to UED W’ search as well (arXiv:1109.1870) • New implementation of PDF and k-factor beyond 2.5 GeV W’ mass underway for this data
Extra Dimension
2011Nov16-19 KIAS Pheno. Workshop
Alternatives to SUSY for resolving the hierarchy problem (MEW << MPlank ?) In this model, gravition can propagate in additional spatial dimensions
Randall-Sundrum KK Graviton
• Dilepton channel
m(G) > 1.8 TeV at 95% CL, for k/MPl = 0.1
2011Nov16-19 KIAS Pheno. Workshop
Randall-Sundrum KK Graviton
• Diphoton channel
m(G) > 1.7 TeV at 95% CL, for k/MPl = 0.1
2011Nov16-19 KIAS Pheno. Workshop
SUSY at the LHC
SUSY predicts supersymmetric partners for SM particles
Leads to the unification of forces
Solves the SM mass hierarchy problem
R-parity conservation leads to a natural dark matter candidate
Squark/Gluino pairs dominated
decays are model dependent
Jets or(and) Leptons or(and) Photons
+ large missing energy (MET)
2011Nov16-19 KIAS Pheno. Workshop
Search Strategy
Generic searches with inclusive topologies for most possible final states : Topology based searches
Several search regions with multiple approaches
Robust data driven background estimates to minimize reliance on MC
Emphasis on discovery over limit setting
2011Nov16-19 KIAS Pheno. Workshop
Jets + MET
95% CL exclusion limits tan =10, > 0, A0 = 0
m0 < 530: M(squark,gluino) 1.25 TeV using Profile Likelihood method
m0 < 500: M(squark,gluino) 1.1 TeV using CLs method
2011Nov16-19 KIAS Pheno. Workshop
CMSSM used as a benchmark model :Four parameters to be dealt with.
m1/2 : universal gaugino mass at GUT scale m0 : universal scalar mass at GUT scale
tanᵦ : VEV ratio for two Higgs doublets A0 : trilinear coupling and the sign of Higgs mixing parameters
Play in [m(1/2), m(0)] plane
Leptons + Jets + MET
2011Nov16-19 KIAS Pheno. Workshop
Single lepton + Jets + MET Require >= 3 jets dramatically
reduce all the backgrounds
Multi-Leptons + MET Almost free from jetty environment and SM low
Excluded region in gluino mass vs wino-like
chargino mass plane for the slepton co-NLSP
scenario
In CMSSM: less strong limits
Photons + Jets + MET
GMSB model LSP is a gravitino
Neutralino is NLSP: mixture of Bino, Wino, Higgsino
Either searching for 2 isolated photons, 1 jets, large MET
Or searching for exactly 1 isolated photon, 3 jets, large MET
Neutralino of mass 375 GeV Bino like Neutralino m < 910 GeV excluded
Wino like Neutralino m < 650 GeV excluded
2011Nov16-19 KIAS Pheno. Workshop
Combined Results
2011Nov16-19 KIAS Pheno. Workshop
Within the Constrained MSSM model, crossing the border of excluding gluinos up to 1TeV and squarks up to 1.25TeV
None of the analysis have observed any significant deviation from the Standard Model
CMS Search Overview
2011Nov16-19 KIAS Pheno. Workshop
No even a single smoking gun yet No evidence for new physics yet Just started !!
2011Nov16-19 KIAS Pheno. Workshop
Summary
The LHC has entered new territory.
No sign of new physics yet in the first ~1 fb-1 at 7 TeV.
Some analyses have been released only with 35 pb-1 so far so these have a lot of headroom left.
The new results with ~ 5 fb-1 expected to be released at the end of Dec 2011 for many channels
The LHC did its part so far with a great first half in 2011 Expect between 10 to 20 fb-1 by the end of 2012, and maybe a higher energy in 2012,which would help for searches.
However some channels are being under watch mode !
Possibility of 8 TeV running ??
Serious discussion on its way right now
2011Nov16-19 KIAS Pheno. Workshop
LHC Schedule Conflict !
Special Shamonix Workshop held in last summer
Shutdown schedule had been
changed Shutdown for two and half
years(originally 1 ½ years) This may cause serious problems
to both CMS and ATLAS
Many so called possible discovery channels will be stuck due to limited COM energy
Pushing further ??? Very plausible to raise energy to 8 TeV with same luminosity target
(~ 10 to 20 fb-1 next year)
G.TONELLI CERN/INFN/UNIPI WGM88 November 16 2011
40
Preliminary Discussion at the last Weekly General Meeting. MB and EB Meetings.
Special General Meeting on November 21st
LPC workshop on November 28 to collect inputs from the experiments before the
traditional Evian (December 12) and Chamonix (February 6) meetings.(2 p.m.)
Machine parameters:
-what energy ? (3.5 TeV, 4 TeV)
-which bunch spacing ? (50ns, 25ns)
-which beta* in IP1/5 ? (0.7m, 1m ?) *
Physics conditions:
-pile-up/background limitations
-sat-main scheme => any issue ?
Physics goals
- priorities ?
-what required integrated luminosity ?
Possibility to increase the energy: 8TeV: benefit everywhere: 10-15% in the low
mass Higgs; x3, x5 in looking for high mass resonances. No controversy here.
Possibility to run at 25ns : definitely better in terms of pile-up: important to know
the cost in terms of integrated luminosity.
Running in 2012: important discussion
2011Nov16-19 KIAS Pheno. Workshop
Epilogue
We may be in the era which is quite uncertain ! However, Let’s wait to understand the nature a little bit more by Human Being !
Once upon a time, there had been an era ruled by dinosaur. Almost definitely, they were perished by asteroid impact !!
Now the mankind are ruling over the earth. There has always been under chaotic state of goodness and badness. Sometimes gathering together to be GOOD.
LHC is a good example of Human being’s goodness. Thousands of people gather together toward one
purpose intercontinentally. It is only for digging the nature’s secret out !