new particle searches in cmsworkshop.kias.re.kr/pheno/?download=donghee kim.pdf · “cern changes...

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


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 ??

?


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)


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 ??


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 !!!


Higgs Production in 7 TeV pp Collsions

gg H is dominant production mechanism


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

https://twiki.cern.ch/twiki/bin/view/CMSPublic/PhysicsResultsHIG


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


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


Intermediate Mass Search 130 < MH<200 H WW 2l 2ν


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)


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


Summary Of All Searches : Expected & Observed

CMS Preliminary • Solid line =

Observed limit • Dashed line =

Expected


SM Higgs Search Combination

• Expected exclusion mass range:

130 – 440 GeV

• Observed exclusion mass range: [145-216] [226-288]

and [310-400] GeV


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


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 !


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 !


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


Dielectron mass spectrum


dimuon mass spectrum


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


Mass limit of Z’s

• Set limits on ratio of cross sections at 95% CL using a Bayesian method



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


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


• 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


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


Randall-Sundrum KK Graviton

• Diphoton channel

m(G) > 1.7 TeV at 95% CL, for k/MPl = 0.1


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)


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


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


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


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


Combined Results


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


No even a single smoking gun yet No evidence for new physics yet Just started !!


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


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


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 !

new particle searches in cmsworkshop.kias.re.kr/pheno/?download=donghee kim.pdf · “cern changes...

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