CCAST Workshop on TeV Physics and the LHC
ITP, Nov. 7, 2006Mike Bisset / 毕楷杰
Co-`workers’:Guan Bian (Tsinghua U.)Nick Kersting, Y. Liu, X. Wang (Sichuan U.)S. Moretti , F. Moortgat (Europe) References:Eur.Phys.J. C45 (2006) 477-492hep-ph/0501157
Beijing, China
Tsinghua University
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Recent convergence in Beyond the SM scenarios
Need to avoid constraints from loop contributions to low energy processes and LEP analyses
pair production of new states
Minimal Universal Extra DimensionsKK-parity in
T-parity insome Little Higgs Models
like R-parity in SUSY
ITP 2006.11.7 克隆克隆
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Spectra of new states expected to be quite different in different models
BUT at LHC only a fraction of the entire spectrum may be identified.
One feature of SUSY --- multiple Higgs boson statesmultiple Higgs boson states that may be singly produced in addition to the pair-produced sparticles
(spins also differ)
(spin may be hard to determine at LHC)
ITP 2006.11.7
MSSM with R-parity conservation:
LSP is stable and invisible
01
(-ino for short)ITP 2006.11.7
How well can we do at the LHC?
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Detecting the lone Higgs Boson of the SStandard MModel
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is a bit more complicated:
Situation in
SUSY MSSM
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only detect h‘‘decouplingdecoupling regime’regime’
the
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BUT depends on good
detection capabilities
for b’s and tau’s
only detect h
LEP II excluded
, ,A H H
signals
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Depends on good
detection capabilities
for b’s and tau’s
only detect h
, muonsH A
Gold-plated signal
LEP II excluded
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try harder we must…
……to feel the FORCE as it flows to usto feel the FORCE as it flows to us from the LHC datafrom the LHC data
ITP 2006.11.7
星球大战 ----尤达
Ahh.., but proceeding pictures take into account Higgs boson decays into sparticles
they do not!
0 0 *, , , , ,i j i jh H A 0 ,i jH
On the dark side…decays to these channels reduce the rates of SM signal channels
On the good side…
new signals they may be found
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0 0 0 02 2 1 1, i i j jH A
4 leptons + signatureE
But if such a signal is observed,But if such a signal is observed, is it really from this decay chain?is it really from this decay chain?
(assumption in several studies thus far)
(2 OS same-flavor pairs)
OneOne channel that has received some attention is:
ITP 2006.11.7
Tsinghua University
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0 02 3 0 02 4 0 03 3
0 03 4
0 02 2 1 1 2 2production f f f f E other
stuff
but also
0 04 4
How much of each?Depends on parameters of the model
1 2, are or f f e
CPS2006
ITP 2006.11.7
M
(GeV
)2
tan 5 , BR , 4 inPP H A H A N fb
1 20.5M Mfrom
gauginounification
400AM GeV
500AM GeV
600AM GeV
light sleptons
Ino sector inputs for the MSSM
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M
(GeV
)2
tan 10 , BR , 4 inPP H A H A N fb 400AM GeV
500AM GeV
600AM GeV
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2M
(G
eV)
tan 20 , BR , 4 inPP H A H A N fb 400AM GeV
500AM GeV
600AM GeV
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2,M ino parameters 2,Mfavor favor heavier ino pairs
ino parameters0 02 2
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MSSM Point 1
MSSM Point 2
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Plus crucial role for sleptons
CPS2006
,
, , ,L R
L R L Re e
m m
m m m m
, ,eA A A
Rm
MSSM inputs of the slepton sector
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rate enhanced
factor of ~5
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What about in mSUGRA ?
0 02 2
0 02 2non-
region
regionITP 2006.11.7
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Now what about non-Higgs boson ‘backgrounds’?
hello
Now what about non-Higgs boson backgrounds?
SM backgrounds can be eliminated mainly through
TE cut coupled with 4 final state
Other SUSY processes?
CPS2006
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Exactly four isolated, high , low leptons TE ore 2.4 7,4GeVTE
Apply CUTs:
four lepton invariant mass cut
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Need to know Higgs bosons masses
…but this is what we seek to discover!
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MSSM Point 2
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ino parameters
favor0 02 2
2,M
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2,Mino parameters
favor heavier ino pairs
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2,Mino parameters
0 02 2
favor
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2,Mino parameters
favor heavier ino pairs
Can also look for charged Higgs bosons
0 0 01 1i j i i j jt H t t
3 Ttop E signature
2 210M GeV
135GeV
/110 / 210m GeV
/ 800 /1000g qm GeV
Set A :Set A :
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Note that in delineating a discovery region for the Higgs bosons,
we are comparing the Higgs signal
at one point in the MSSM parameter space to MSSM `backgrounds’
at the samethe same point in the MSSM parameter space
Could a Higgs excess
postulated for one point really be due to increased backgrounds at another point?
Consider different ways in MSSM to produce a pair of inos
我
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老毕
未知
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1 1, a b i i j jH A E4 leptons + signature
but restrict ourselves but restrict ourselves to leptons pairs of distinct flavorsto leptons pairs of distinct flavors
(2 OS same-flavor pairs)
ITP 2006.11.7
( , 1)
0 0 stuffi j
p p e e Ei j
Now consider all methods of producing –ino pairs
It turns out that this restriction is not really necessary, but it simplifies the analysis.
other stuff
Ino Pair Production Modes:
‘direct’ Higgs-mediated colored-sparticle cascade decays
Rates generally smaller
Rates may be large if heavier MSSM Higgs bosons
are in the right zone
Largest potential ratesdue to strong production cross-sectionsEspecially if gluinos (and squarks) are relatively light.
0 0 0, (but not )H A h
400 500 GeVgm
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jetty
Tsinghua University
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At a hadron collider, cannot set energy for the parton-level processunlike at a linear collider where one can scan up incrementally in to cross each threshold sequentially one at a time
e e
cmE0 0i j
0 0i j So just must deal with different states
being produced simultaneously at different rates
Need to disentangle theseITP 2006.11.7
Tsinghua University
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( )M e e
M
box-like shape0 0i i
0 0i j
for production
wedge-like shapefor production
( )i j
for our process types
ITP 2006.11.7
coin the name `wedgebox plot’
also Z-Line:
01
01
0 ~~~ llZi
decay via off-shell or charged slepton
0*Z
Consider WEDGEBOX PLOTS
eeM
M
01
0 ~~ mmi
01
0 ~~ mmi
01
0 ~~ mmi
01
0 ~~ mm
j
Zm
Zm
BOX (i = j) WEDGE (i != j)
Z-Line:
)~2~~( 01
00 eeji
*On shell sleptons:
2~
2~
2~
2~
~
01
0
0 11l
l
m
m
m
mm
i
i
01
01
0 ~~*~ llZi or0
10 ~*
~~ lllli
01
01
0 ~~~ llZi
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Possible Wedgebox Plots:
Could be 0 02 2
0 03 3
0 04 4
or
or
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Complications
Assumes0i e NONO
NONO
other stuff
0
0
i
j
e e
0 stuffi jp p
other stuff
just other stuff (no leptons)
Typically these decay modes are small to negligibly tiny.
Neglects charginosAlong with leptons from decaying top quarks that might happen to be produced.
stuffi jp p stuffi jp p
ITP 2006.11.7
While not yet included in the framework we’ve developed for possible wedgebox plot topologies, we do understand the distributions obtained from such processes fairly well.
& slepton pair production
Tsinghua University
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Gluino/squark pair production with cascade decays
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charginoscharginos!!!
Note: these are inclusive 4-lepton rates with no cuts ore
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simulate signals and backgrounds
realistic calorimeter simulation package (recent CMS package)
with HERWIG 6.5 event generatorcoupled to
Now actually
From Table can determine relative rates for different –ino pairs
Point C: 22 33 44: : 131.5 :1.3 :1r r r
23 24 34: : 10.2 : 9.6 :1r r r
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Resulting Wedgebox plots
MSSM Point A
envelope-types
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MSSM Point A
Hard edges
3-body decay0 02 142.8 GeV massdifference
0 02 1( ) 0.245BR
off-shell sleptons very important
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MSSM Point A
Here sleptons on mass-shell
two-body decays
End points no longer -ino mass differences
0 * 01,i
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“stripe”
MSSM Point A
Note change in event density around 85 GeV
0 02 3 production
or a 0 0 04 2 1 other
stuff
E22.8% of the time
ITP 2006.11.7
0 02 2 0 03 3 0 04 4
or
or
IIIIIIji ll ,,
00 ~~
03,2
04
~~
1 + 3
02
03
~~
+ 2
+ (2)(3) + 6
+ (2)(6) = 30
How many Wedgebox Plots?
With infininte luminosity, see a 6x6 checkerboard
ITP 2006.11.7
MSSM Point A“maverick events”
These events are not expected within out neutralino-only framework for predicting Wedgebox plots
Study of the detailed HERWIG output for such generated events confirmed that leptons in these events come from charginos
in addition, there were other exceptional features of these points ITP
2006.11.7
MSSM Point B
envelope-types
ITP 2006.11.7
MSSM Point B
Double the luminosity
Two heavy –inos very close in mass
ITP 2006.11.7
MSSM Point B
Note: squark production is required to account for these events
0 02 4
ITP 2006.11.7
MSSM Point C
envelope-types
Try to reconstruct
production rate leptonic BRrates for different –ino pairs
MSSM Point C
from 6 observables:
, , , , ,
Assuming triangular population density distributions:
# of
ev
ents
Point C: 55
55
96
96
173
173
for :44re.g.,
(GeV)
( )M
'sijr
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Fact : rates of getting via direct production are extremely small0 02 2
Next consider the electroweak production processes
Use jet cut to remove cascade decays from gluino/squark pair production (or make colored sparticles very heavy)
ITP 2006.11.7
coupling suppressed
Only one pair combination, can lead to an appreciable rate
(sufficient to adequately populate a wedgebox plot)
Other pairs are too phase-space suppressed
0 02 3
No direct production boxes !!!
2 2
3 4
* *3 3 4 4
| Re2cos
| Re2cos
i i i iW
i j i j i jW
gZ N N
gZ N N N N
Tsinghua University
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ITP 2006.11.7
0 02 3
0i j
direct
from0 0,A H
i j
chargino chargino pairs
direct
directchargino chargino neutralinopairs
only meaningfulcontributor !!!
Must lose lepton or jets
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MC results: See two islands with rates over 100 events for 1100 fb
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Separated by `spoiler’ canal
tan 10
Rate Can be Larger
Scanned GeVmGeVl
300120,50tan5 ~ ITP 2006.11.7
tan 10 tan 5 tan 20
02
m m m
canal of Spoiler mode
1300 fbL
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Revised version:
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Comments:
In regions of upper island where double wedge is seen, will be able to extract 3 mass differences with reasonable precision.This will allow determination of the 3 input parameters of the neutralino mixing matrix if the slepton parameter(s) are under control.
2 , , and tanM
0 02 3 Direct production produces a wedge
Slepton pair production also produces wedgesCharginos can produce boxes, but only for low 2 &M
(lower island)
If one observes a box in the experimental wedgebox plot, then either one has seen evidence of a heavier Higgs boson or are both rather small.
2 &M An (almost) parameter-space independent statement.
ConclusionsLet me go!!!
Have shown can extract substantial information on the MSSM –ino mass spectrum
But beware of assuming hard edges = -ino mass differences
Sleptons must also be considered as key playersITP
2006.11.7
Wedgebox plots:
Heavier MSSM Higgs boson search techniques via decays to SM particles inadequate
Full consideration of Higgs boson decays into sparticles makes accessible large new regions of the MSSM parameter space
0 0, :,A H H
A
B
C
Traditional 1-Dim plots2-D
im D
alitz-like p
lots
2-D plots give quick visual impression of which –ino pairs are being significantly produced
Obvious advantages over traditional 1-D plots ITP 2006.11.7
e e Undoubtedly, will still require a ~TeV scale linear collider to fully sort things out and do better precision measurements.
…but that may well take
another years to be realized.ITP 2006.11.7
The topology or pattern of the wedgebox plot maymay tell us where we are in the parameter space and whether or not heavy Higgs bosons are being produced.
Parameter-space dependent cuts may then be applied to purify a sample of 4 lepton events from a specific process.
Potential applicability of this methodology to other beyond the SM scenarios with conserved Q.#’s that demand pair production of a spectrum of new particles
The End
Thank you for listening!!!
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ITP 2006.11.7
MUED’s Minimal universal extra dimensions
All SM fields propagate in a single compactified extra dimension
with compactification radius near the TeV scale
All SM particles have KK partners with similar couplings
The lowest KK level particles carry a conserved quantum numberKK-parity
The lightest KK particle is the stable LKP
The LKP is not detected, resulting in a missing energy signal.
(lowest energy states in the Kaluza-Klein towers)
Sounds a lot like the MSSM, no?
First consider something that is NOTNOT supersymmetry ---
H.-C. Cheng, Matchev & Schmaltz hep-ph/0205314
Distinctions between the MSSM and MUED’s
Sparticles have different spins from their SM partnerswhile KK particles have the same spin
This would certainly be testable at a LC, but at the LHC maybe not
There is no analog to the heavier MSSM Higgs bosons
The KK partners to the Higgs carry KK-parity, and so should be pair produced (behaving more like Higgsinos than like Higgs bosons)
Smillie & Webber hep-ph/0507171
Barr, hep-ph/0405052limited attempts:
So we see detection of the heavier MSSM Higgs bosons
is crucial for even being sure that we are seeing
SUPERSYMMETRY
Calculation: 01
00 ~2~~ eeji
03
02
~~ Plot: number of e+e- endstates for L=100 fb-1
Only is significant03
02
~~
ee from
* *3 3 4 4
* *3 3 4 4
| Re2cos
| Re2cos
i j i j i jW
i i i i i iW
gZ N N N N
gZ N N N N
Calculation
:
Signficant decays to heavier neutralinos
01
0000 ~2~~, eeAH ji
ee from00 , AH
SUSY BG Calculation:0
10 ~2~~,~~ eejiji
ee eefrom from22
~~ 0~~ji
Monte Carlo• Herwig v6.5
– Inputs from ISASUSY (ISAWIG, HDECAY)– CTEQ6 PDF ( )
• Simulate typical (eg. CMS) detector environment• Private Codes
– Select e+e-+- events• • • each lepton must be isolated
– no charged tracks with within a cone of radius 0.3 rad of each lepton
– energy deposited in electromagnetic calorimeter is less than 3 GeV for 0.05 < r < 0.3
JET VETO eliminates squarks/gluinos
20 < MISSING E_T <130 GeV SUSY BG
GeVpeT 8,10,
4.2, e
GeVpT 5.1SM BG
ExceptZZ*
0~~~~jiji
tHll ~~
GeVmGeVm bt 25.4,175
Double-Wedge: straightforward
Slepton splitting: 2,12,12~
2~
2~
2~
~~,~~
,1101
0
0
elm
m
m
mm
l
l
i
i
01
04
~~
01
03
~~
01
02
~~
Understand Contributions to the Double-Wedge
• Higgs Component
• Chargino Component
01
~, 2
mm AH
0~~ji
03
02
~~
003
02
~~~~ji
Agenda
Use LHC to measure MSSM Parameters as accurately as possible– If Low Energy SUSY is correct, the gluino and
squarks will be seen– Sleptons, neutralinos
lmM ~2,1 ,tan,,
Tji Eee
anythingpp
00 ~~
i,j=2,3,4
Base MSSM Parameters
• Heavy Colored Sparticles
• Optimal Higgs
• Light Selectrons/Smuons
• Other– R-parity, No Flavor Mixing
GeVm
GeVm
RL
RL
l
l
250
150
,3
,2,1
~
~
GeVmA 600
GeVm
GeVm
q
g
1000
800
~
~
22
1 tan3
5MM W
10tan RELAX THESE PARAMETERS LATER
Discovery region (for signals)
x 7
Different Wedge-box structure in
diffenent districts
e e
1. Neutralino PP
2. Direct channel
4.Tau signatures
3. I WB plot
Spoiler mode 0 02 1( )or
02
M M 0
2 lM M
1. Neutralino PP
2. Direct channel
4.Tau signatures
3. I WB plot
Selection rules
• 1.Choose smaller sum of the invariant masses of two pairs.
• 2. Choose smaller opening angle between (or ).
• Efficiency to choose the “correct” pairs ~ 80%
Powerful enough to reconstruct the wedge-box structure.
e e
1. Neutralino PP
2. Direct channel
4.Tau signatures
3. I WB plot
Simulation result
2
:
tan 10
210( )
280( )
2000( )
3000( )
150( )
250( )
2500( )
A
q
l
g
MSSM parameters
GeV
M GeV
M GeV
M GeV
M GeV
M GeV
M GeV
1. Neutralino PP
2. Direct channel
4.Tau signatures
3. I WB plot
Improved wedge-box plot method
• With this method, we can get :
3. investigation of signals
1. more explicit wedge-box structure
2. enlarged discovery region
1. Neutralino PP
2. Direct channel
4.Tau signatures
3. I WB plot
• coupling is suppressed
• Same reason kills
plus more phase space supression.
dominance in direct channel0 02 3
0 03 3
2 20 03 4| Re
2cosi i i iW
gZ N N
0 02 2Z
Higgsino components cancel
0 0 * *3 3 4 4| Re
2cosi j i j i jW
gZ N N N N
i j
Cancellation less severe
1. Neutralino PP
2. Direct channel
4.Tau signatures
3. I WB plot
Salient points about (c):
Produces jets, cannot be hadronically quiet
No fundamental vertex0 0i jS
each –ino produced independently
reduction in number of possible patterns
IF -ino pair production is only due to gluinos
possible on Dalitz-like plots
APFB05
Know and rates know rate. 0 0i i 0 0
j j 0 0i j
But squarks can also contribute significantly!!
2ij i jr r r
(or only one kind of colored sparticle)
APFB05
Beenacker et al., NPB 492 (1997) 51
APFB05
EW gaugino unification
endpoints become bands
Sleptons relatively light to enhance leptonic BRs
APFB05
APFB05
hep-ph/0501157
APFB05
simulate signals and backgrounds
realistic calorimeter simulation package (recent CMS package)
with HERWIG 6.5 event generatorcoupled to
Now actually
From Table can determine relative rates for different –ino pairs
Point C: 22 33 44: : 131.5 :1.3 :1r r r
23 24 34: : 10.2 : 9.6 :1r r r
APFB05
CUTS
Note: lose up to 90% of inclusive 4-lepton events mostly due to one or more leptons being too soft.
Simple set of
APFB05
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APFB05
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charginoscharginos!!!
Note: these are inclusive 4-lepton rates with no cuts ore
APFB05
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Now what about non-Higgs boson backgrounds?
Look at processes of the type
1 1 2 2stuffp p X X f f f f
other stuff
Pair production of new heavy states
Decay to SM fermion pairs
Required by some new symmetry of the SM extension
e.g.’s: R-parity in SUSYconservation
ZZ22
-symmetry in little Higgs models FCNC
KK-parity in MUED’s
?X T-parityHubisz & Meade
hep-ph/0411264
the upcoming look beyond the Standard Model (SM)
at the soon-to-commence LHC
Minimal universal extra dimensionsH.-C. Cheng, Matchev & Schmaltz hep-ph/0205314
APFB05
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APFB05
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