1. On
the
W+4
jets
background
to
the
top-‐
quark
asymmetry
at
the
Tevatron
Yoshitaro
Takaesu
KEK,
Japan
In
collaboraDon
with
K.
Hagiwara
(KEK)
and
J.
Kanzaki
(KEK),
in
preparaDon
2. IntroducDon
• Large
top
forward-‐backward
asymmetry
(
)
has
been
observed
at
the
Tevatron.
• Contribu>ons
of
NNLL
QCD,
EW
correc>ons,
NLO
of
,
etc.
have
been
discussed,
but
we
do
not
know
the
sa>sfactory
answer
yet.
• We
focus
on
W+4
jets
background
for
this
anomalous
.
May
7,
2012
2
PHENO
2012:
Yoshitaro
Takesu
11. Summary
• We
inves>gated
W+4
jets
background
in
detail
on
,
and
distribu>ons.
• Large
is
seen
in
W+4
jets
background.
• Anomaly
in
by
D0
may
suggests
BG
contamina>ons
in
signal
than
expected.
• We
suggest
to
re-‐evaluate
W+4
jets
BG
at
the
Tevatron,
comparing
with
distribu>ons
we
discussed.
May
7,
2012
11
PHENO
2012:
Yoshitaro
Takesu
14. Reconstruc>on
of
top
For
the
other
W
Select
W
candidates
(j1,j2)
b1
=
b-‐tagged
jet
b2
=
b-‐tagged
jet
(
if
#
b
=2
)
the
remained
jet
(
if
#
b
=1
)
use
4
leading
jets
(including
b-‐tagged
jet)
for
reconstruc>ons
If
no
candidate,
throw
away
the
event
May
7,
2012
14
PHENO
2012:
Yoshitaro
Takesu
15. ReconstrucDon
of
top
&
anDtop
May
7,
2012
PHENO
2012:
Yoshitaro
Takesu
15
+
i=l,jets
pi,meas
T pi
T
2
i
2
+
j=x,y
pUE,meas
j pUE
l
2
j
2