CCAST Workshop on
TeV Physics and the LHC
ITP, Nov. 7, 2006
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) 477-492
hep-ph/0501157
Mike Bisset / 毕楷杰
Tsinghua University
Beijing, China
清华大学 Tsinghua University
Need to avoid constraints from
loop contributions to low energy processes
and LEP analyses

Recent convergence in Beyond the SM scenarios
KK-parity in
Minimal Universal Extra Dimensions
T-parity in
some Little Higgs Models
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2006.11.7
pair production
of new states
like
R-parity
in SUSY
克隆
清华大学 Tsinghua University
Spectra of new states expected to be quite different
in different models
(spins also differ)
BUT at LHC only a fraction of the entire spectrum may be identified.
(spin may be hard to determine at LHC)
One feature of SUSY --- multiple Higgs boson states
that may be singly produced
in addition to the pair-produced sparticles
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MSSM
with R-parity conservation:
LSP is stable and invisible

0
1
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(-ino for short)
How well can we do at the LHC?
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2006.11.7
Detecting the lone Higgs Boson of the
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2006.11.7
Standard Model
Situation in
SUSY MSSM
is a bit
more complicated:
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2006.11.7
only detect
h
the
‘decoupling
regime’
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2006.11.7
A, H , H 
signals
only detect
LEP II excluded
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h
H , A  muons
Gold
-plated
signal
only detect
LEP II excluded
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h
try harder we must…
星球大战---尤达
…to feel the FORCE as it flows to us
from the LHC data
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2006.11.7
Ahh.., but proceeding pictures
take into account
Higgs boson decays into sparticles
they do not!
h, H , A    ,   ,
0
i
H   i  0j ,

i
0
j

j
 
,
*


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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2006.11.7
清华大学 Tsinghua University
One channel that has received some attention is:
0 0
   
0 0
H , A  2 2  i i j j 1 1
4 leptons +
(2 OS same-flavor pairs)
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2006.11.7
E
signature
But if such a signal is observed,
is it really from this decay chain?
(assumption in several studies thus far)
清华大学 Tsinghua University
At LHC, can have
 20  20 production 
but also
 20  30
other
f
f

f
f

E

stuff
 1 1  2 2 
f1 , f 2 are e  or  
 20  40
 30  30
 
0
3
0
4
 40  40
How much of each?
Depends on parameters
of the model
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2006.11.7
CPS2006
tan   5
  PP  H , A   BR  H , A  4 N  in fb
M2 (GeV)
M A  400 GeV
M1
M A  500 GeV
M A  600 GeV
0.5M 2
from
gaugino
unification
light
sleptons
Ino sector
inputs
for the
MSSM
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tan   10
  PP  H , A   BR  H , A  4 N  in fb
M2 (GeV)
M A  400 GeV
M A  500 GeV
M A  600 GeV
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tan   20
  PP  H , A   BR  H , A  4 N  in fb
M2 (GeV)
M A  400 GeV
M A  500 GeV
M A  600 GeV
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 , M 2 ino parameters
favor
 20  20
 , M 2 ino parameters
favor heavier ino pairs
MSSM Point 2
MSSM Point 1
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2006.11.7
清华大学 Tsinghua University
Plus crucial role for sleptons
MSSM inputs of the slepton sector
m L , m R
meL , meR , mL , mR
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m
R
Ae , A , A
CPS2006
rate enhanced
factor of
~5
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What about in mSUGRA ?
non- 20  20
region
 20  20
region
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2006.11.7
清华大学 Tsinghua University
Now
what about non-Higgs boson backgrounds?
Now what about non-Higgs boson ‘backgrounds’?
SM backgrounds can be eliminated mainly through
ET cut
coupled with 4
hello
final state
Other SUSY processes?
CPS2006
清华大学 Tsinghua University
Identify candidate event:
 Exactly four isolated, high ET , low 
ET  7, 4GeV   2.4
Apply CUTs:
 four lepton invariant mass cut
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2006.11.7
leptons
e or  
清华大学 Tsinghua University
Four lepton invariant mass cut
Need to know Higgs bosons masses
…but this is what we seek to discover!
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2006.11.7
清华大学 Tsinghua University
MSSM
Point 1
MSSM
Point 2
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清华大学 Tsinghua University
 , M2
ino parameters
favor
 20  20
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清华大学 Tsinghua University
 , M2
ino parameters
favor
heavier ino pairs
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2006.11.7
清华大学 Tsinghua University
 , M2
ino parameters
favor
 20  20
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清华大学 Tsinghua University
 , M2
ino parameters
favor
heavier ino pairs
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Can also look for charged Higgs bosons
Set A :
M 2  210 GeV
  135GeV
m
/
 110 / 210 GeV
mg / q  800 /1000 GeV
t  H   t  i  0j  t  i

i
 
j j
10 10
3  top  ET signature
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2006.11.7
清华大学 Tsinghua University
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
same point in the MSSM parameter space
Could a Higgs excess
postulated for one point
really be due to increased backgrounds
at another point?
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2006.11.7
Consider different ways in MSSM to produce a pair of inos
老毕
我
未
知
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2006.11.7
清华大学 Tsinghua University
H , A  a0 b0 
 
i i
 
j j
10 10

4 leptons + E
signature
(2 OS same-flavor pairs)
Now consider all methods of producing –ino pairs
pp
other
0 0
 
 

stuff

e
e




E

   
stuff
i j
( i , j 1)
but restrict ourselves
to leptons pairs of distinct flavors
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It turns out that this restriction
is not really necessary,
but it simplifies the analysis.
Ino Pair Production Modes:
‘direct’
Higgs-mediated
Rates generally
smaller
Rates may be large
if heavier MSSM
Higgs bosons
H 0 , A0 (but not h0 )
are in the right zone
colored-sparticle
cascade decays
Largest potential rates
due to strong production
cross-sections
Especially if
gluinos (and squarks)
are relatively light.
mg  400  500 GeV
jetty
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2006.11.7
清华大学 Tsinghua University
Facts of life at the LHC:
At a hadron collider,
cannot set energy for the parton-level process
 
unlike at a linear e e collider
where one can scan up incrementally in Ecm
0 0
to cross each i  j threshold sequentially one at a time
0 0

So just must deal with different i  j states
being produced simultaneously at different rates
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2006.11.7
Need to disentangle these
清华大学 Tsinghua University
Topologies on Dalitz-like plot
for our process types
box-like shape
for
 
0
i
M       decay via off-shell Z
or charged slepton
0*
0
i production
M (e  e  )
wedge-like shape
for 
0
i

(i  j )
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also Z-Line:
0
production
j
~i0  Z  ~10  l l   ~10
coin the name `wedgebox plot’
Consider
~ 0 ~ 0  e e      2~ 0 )
(

WEDGEBOX PLOTS i ~ j
1
~i0  Z *  ~10  l l   ~10
M   
or
WEDGE (i != j)
BOX (i = j)
m~ 0  m~ 0
m~ 0  m~ 0
i
~i0  l  * l   l  l   ~10
j
1
m~ 0  m~ 0
i
m~ 0  m~ 0
i
*On shell
sleptons:
m~ 0 1 
i
m~l2
m
2
~ 0
i
1
1
M ee
1
Z-Line:
m2~ 0
1
~i0  Z  ~10  l l   ~10
1
2
~
l
m
mZ
mZ
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Possible
Wedgebox
Plots:
Could be
 
0
2
0
2
or
 
0
3
0
3
or
 
0
4
0
4
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Complications
Assumes
 NO   e  
0
i

other
stuff
0
   
other


e
e



stuff
 NO i
 0j  just other stuff (no leptons)
Typically these decay modes
are small to negligibly tiny.
Neglects charginos  

p p  i  j  stuff
Along with leptons
from decaying
p p  i  j  stuff
top quarks that
might happen to

0
p p  i  j  stuff
be produced.
&
slepton
pair production
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.
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2006.11.7
清华大学 Tsinghua University
First consider production processes with the largest rates…
Gluino/squark pair production
with cascade decays
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2006.11.7
清华大学 Tsinghua University
charginos!!!
Note: these are inclusive 4-lepton rates with no cuts
e

or   
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From Table can determine relative rates for different –ino pairs
Point C: r22 : r33 : r44 131.5 :1.3:1
r23 : r24 : r34
10.2 : 9.6 :1

Now actually
simulate signals
and backgrounds
with HERWIG 6.5 event generator
coupled to
realistic calorimeter simulation package
(recent CMS package)
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Resulting
Wedgebox plots
envelope-types
MSSM
Point A
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Hard edges
MSSM
Point A
3-body decay
42.8 GeV  20  10 mass difference
BR(  20  10
 
)  0.245

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
i0 



,
*

 
 10
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MSSM
Point A
Note change
in event
density
around
85 GeV
  production
0
2
0
3
or a “stripe”
 
0
4
22.8%
of the time
 
0
2
 

 
 
E
0
1
other
stuff
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How many Wedgebox Plots?
0
0


or 20 20
 
or 30 03
4 4
~i0  ~0j  lI,II  lI, II
~0  
~0

3
4
2, 3
1 +3 +2
+ (2)(3) + 6
+ (2)(6) = 30
With infininte luminosity, see
a 6x6 checkerboard
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“maverick events”
MSSM
Point A
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
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2006.11.7
MSSM
Point B
envelope-types
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MSSM
Point B
Double the luminosity
Two heavy –inos
very close in mass
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MSSM
Point B
Note: squark production is required 0
to account for these  2

0
4 events
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MSSM
Point C
envelope-types
Try to reconstruct
production rate  leptonic BR  rij 's

rates for different –ino pairs
from 6 observables:
 ,  ,  ,  , , 
  
  
  
173
e.g.,
96
55
# of events
MSSM
Point C
Assuming triangular
population density
distributions:
r
for 44 :
M(
Point C: 55 96
173
 
)
(GeV)
清华大学 Tsinghua University
Next consider the electroweak production processes
Use jet cut to remove cascade decays
from gluino/squark pair production
(or make colored sparticles very heavy)
Fact : rates of getting
 20  20 via direct production are extremely small
 
0
2
Only one pair combination,
can lead to an appreciable rate
0
3
coupling suppressed
g
Z|  
Re  N  N 
2 cos 
2
i
i
i3
2
i4
W
Z | i  j 
(sufficient to adequately
populate a wedgebox plot)
g
Re  N i 3 N *j 3  N i 4 N *j 4 
2 cos W
Other pairs are too phase-space suppressed

No direct production boxes !!!
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2006.11.7
清华大学 Tsinghua University
Parton level scan of inclusive rates:
direct
 20 30
only
meaningful
contributor !!!
from
A0 , H 0
direct
chargino
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neutralino
pairs
0 
i
j
Must lose
lepton
or jets
 
direct
chargino
pairs
i  j
清华大学 Tsinghua University
MC results:
tan   10
See two islands
with rates over 100 events
1
for 100 fb
Separated
by
`spoiler’
canal
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Rate Can be Larger
Scanned
5  tan   50,
120 GeV  m~l  300 GeV
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tan   5
tan   10
canal of Spoiler mode
m  m 0  m 
2
tan   20
L  300 fb1
清华大学 Tsinghua University
Revised
version:
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2006.11.7
清华大学 Tsinghua University
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 M 2 ,  , and tan 
if the slepton parameter(s) are under control.

Direct  2  3 production produces a wedge
Slepton pair production also produces wedges
Charginos can produce boxes, but only for low
0
0
M2 & 
(lower island)
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If one observes a box in the experimental wedgebox plot,
then either one has seen evidence of a heavier Higgs boson
or M 2 &  are both rather small.
An (almost) parameter-space independent statement.
Conclusions
Let me go!!!
A0 , H 0 , H  :
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
Wedgebox plots:
Have shown can extract
substantial information
on the MSSM –ino mass spectrum
But beware of assuming
hard edges = -ino mass differences
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Sleptons
must also be considered
as key players
Traditional 1-Dim plots
B
C
2-Dim Dalitz-like plots
A
2-D plots give quick visual impression
of which –ino pairs are being
significantly produced
Obvious advantages over traditional 1-D plots
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The topology or pattern of the wedgebox plot may 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
Undoubtedly, will still require a
 
~TeV scale e e linear collider
to fully sort things out and
do better precision measurements.
…but that may well take
another
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2006.11.7
years to be realized.
The End
Thank you for listening!!!
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2006.11.7
清华大学 Tsinghua University
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2006.11.7
First consider something that is NOT supersymmetry ---
MUED’s Minimal universal extra dimensions
H.-C. Cheng, Matchev & Schmaltz hep-ph/0205314
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
(lowest energy states in the Kaluza-Klein towers)
quantum number
 The lowest KK level particles carry a conserved
KK-parity

The lightest KK particle is the stable LKP
The LKP is not detected, resulting in a missing energy signal.
Sounds a lot like the MSSM, no?
Distinctions between the MSSM and MUED’s
 Sparticles have different spins from their SM partners
while KK particles have the same spin
This would certainly be testable at a LC,
but at the LHC maybe not
limited attempts: Barr, hep-ph/0405052
Smillie & Webber hep-ph/0507171
 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)
So we see detection of the heavier MSSM Higgs bosons
is crucial for even being sure that we are seeing
SUPERSYMMETRY
Calculation:
0 ~0
   
0
~
~
   e e    2
i
j
1
ee    
Plot: number of e+e-
endstates for L=100 fb-1
~ 0 ~ 0

Only 2 3 is significant
Z | i  j 
g
Re  Ni 3 N *j 3  Ni 4 N *j 4 
2 cos W
Z | i i 
g
Re  N i 3 N i*3  N i 4 N i*4 
2 cos W
from
~20 ~30
Calculation:
ee    
H 0 , A0  ~i0 ~ 0j  e e      2~10
from
H 0 , A0
Signficant decays to
heavier neutralinos
~  ~  , ~  ~ 0  e  e       2 ~ 0

SUSY BG Calculation:
i
j
i
j
1
ee    
from
~2 ~2
ee    
from
~i ~ 0j
• Herwig v6.5
Monte Carlo
– Inputs from ISASUSY (ISAWIG, HDECAY)
– CTEQ6 PDF ( mt  175 GeV , mb  4.25 GeV )
• Simulate typical (eg. CMS) detector environment
• Private Codes
– Select e+e-+- events
e, 
p
• T  10, 8 GeV
•  e ,   2 .4
SM BG
Except
ZZ*
• each lepton must be isolated
– no charged tracks with pT  1.5 GeV 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
~  ~  ~  ~ 0 ~l  ~l  tH
20 < MISSING E_T <130 GeV SUSY BG 
i
j
i
j
Double-Wedge: straightforward
~40  ~10
~30  ~10
~20  ~10
Slepton splitting:
m~ 0 1 
i
2
~
l
2
~ 0
m
m
i
1
m2~ 0
1
m~l2
~ ~ ~
, l  e1, 2 , 1, 2
Understand Contributions to the Double-Wedge
• Higgs Component
mH , A  2m~ 0
~20 ~30  ~i ~ 0j
1
• Chargino Component
~20 ~30
~i ~ 0j
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
M 1, 2 ,  , tan  , m~l
pp  anything 
0 ~0
   
~
  e e   E
i
j
T
i,j=2,3,4
Base MSSM Parameters
• Heavy Colored Sparticles
mg~  800 GeV
mq~  1000 GeV
• Optimal Higgs
mA  600 GeV
• Light Selectrons/Smuons
m~l L ,R  150 GeV
1, 2
m~l L ,R  250 GeV
3
• Other
– R-parity, No Flavor Mixing
RELAX THESE PARAMETERS LATER
5
M 1  tan 2 W M 2
3
tan   10
  
 
Discovery regionee(for
1. Neutralino PP
signals)
Different Wedgebox structure in
diffenent districts
2. Direct channel
3. I WB plot
x7
4.Tau signatures
20 
  (or   )  10  
Spoiler
mode
1. Neutralino PP
2. Direct channel
3. I WB plot
4.Tau signatures
M  0  M
2
M 0  Ml 
2
Selection rules
1. Neutralino PP
2. Direct channel
•
1.Choose smaller sum of the invariant
masses of two pairs.
•
2. Choosee smaller
opening angle
e
between
(or    ).
•
Efficiency to choose the “correct” pairs ~
80%
Powerful enough to reconstruct the
wedge-box structure.
 
3. I WB plot
4.Tau signatures
Simulation result
1. Neutralino PP
MSSM parameters :
tan   10
  210(GeV )
M 2  280(GeV )
2. Direct channel
M A  2000(GeV )
M q  3000(GeV )
M l  150(GeV )
M   250(GeV )
3. I WB plot
4.Tau signatures
M g  2500(GeV )
Improved wedge-box plot method
•
With this method, we can get :
1. Neutralino PP
1. more explicit wedge-box structure
2. enlarged discovery region
2. Direct channel
3. I WB plot
4.Tau signatures
3. investigation of

   
signals
 20  30
1. Neutralino PP
2. Direct channel
dominance in direct channel
• Z  20  20 coupling is suppressed
g
2
2
Z |  i0  i0 
Re N i 3  N i 4
2 cos W


Higgsino components cancel
3. I WB plot
4.Tau signatures
Z | i0  0j 
g
Re  Ni 3 N *j 3  Ni 4 N *j 4 
2 cos W
Cancellation less severe
30 30
• Same reason kills
plus more phase space supression.
i j
Salient points about (c):
 Produces jets, cannot be hadronically quiet
0
0
 No fundamental S  i   j vertex
 each –ino produced independently

reduction in number of possible patterns
possible on Dalitz-like plots
IF -ino pair production is only due to gluinos
APFB05
Know
 i0  i0
and 
0
j

0
j
rates
0 0

 know i  j
rate.
(or only one kind of colored sparticle)
rij  2  ri rj
But squarks can also contribute significantly!!
APFB05
Beenacker et al.,
NPB 492 (1997) 51
APFB05
EW gaugino unification
Sleptons
relatively light
to enhance
leptonic BRs
 endpoints
become bands
APFB05
APFB05
hep-ph/0501157
APFB05
From Table can determine relative rates for different –ino pairs
Point C: r22 : r33 : r44 131.5 :1.3:1
r23 : r24 : r34
10.2 : 9.6 :1
Now actually
simulate signals
and backgrounds
with HERWIG 6.5 event generator
coupled to
realistic calorimeter simulation package
(recent CMS package)
APFB05
Simple set of
CUTS
Note:
lose up to 90%
of inclusive
4-lepton events
mostly due to
one or more
leptons being
too soft.
APFB05
清华大学 Tsinghua University
ITP
2006.11.7
清华大学 Tsinghua University
APFB05
清华大学 Tsinghua University
charginos!!!
Note: these are inclusive 4-lepton rates with no cuts
e

or   
APFB05
清华大学 Tsinghua University
the upcoming look beyond the Standard Model (SM)
at the soon-to-commence LHC
Now what about non-Higgs boson backgrounds?
Look at processes of the type
p p  X X  stuff   f1 f1    f 2 f 2 
Pair production
of new heavy states
other
 stuff
Decay to
SM fermion pairs 
Required by some new symmetry of the SM extension
e.g.’s:  R-parity in SUSY

KK-parity in MUED’s
Minimal universal extra dimensions
H.-C. Cheng, Matchev & Schmaltz
hep-ph/0205314
conservation

Z2-symmetry in little Higgs models  FCNC
T-parity
Hubisz & Meade
hep-ph/0411264
APFB05
X ?
清华大学 Tsinghua University
Collapse to a point
APFB05