Evidence of single top quark production at Fermilab Tevatron
Oleh : Haryo Sumowidagdo
Kamis, 21 Desember 2006 (16:36 WIB) dari IP 125.160.98.240

During the Fermilab Wine and Cheese weekly seminar last Friday, D0
reported the first evidence of single top quark production and the same
time a direct measurement of the CKM matrix element V_tb.

See the seminar transparancies at

http://www-d0.fnal.gov/Run2Physics/WWW/results/prelim/TOP/T39/wine_and_cheese.pdf

Background information:

Top quarks can be produced at Tevatron via two different mechanism.
The first is via strong interactions. Here, in the initial state either
quark-antiquark pair or gluon pair in the colliding protons-antiprotons
annihilate into gluon intermediate state which produces a top
quark-antiquark. This production mechanism has been observed and
measured to a good precision.

The second production mechanism is more subtle and difficult to observe.
Here top quark is produced singly in the final state together with a
b-quark, with a W boson in the intermediate state.

The challenges faced by the D0 single top analysis team of more than 30
physicists is tremendous. Even after all the very tight selection
criteria applied, the signal to background ratio is still on the order
of 1:20. They had to apply sophisticated analysis techniques to extract
the signal from data.

Single top quark production has utmost importance due to many things.
It is the primary background to Standard Model Higgs search. It provides
direct measurement of CKM matrix V_tb. It is a probe to non-SM physics
since single top quark production is sensitive to non-SM physics.

A draft of Physical Review Letter article is in the review stage, wait
for further update.

It is nice to acknowledged that this important evidence is the results
of the work of many people, as many as 700 people of different
nationality, ages, expertises, experiences, from all over the world.
There are experimentalists, theorists, engineers, students, professors.
Some of them have dedicated more than 10 years in this search.

Kelanjutan dari berita single top quark

http://www.fnal.gov/pub/presspass/press_releases/Single-Top.html

Sekedar selingan: Hari Jum'at lalu waktu seminar yang mengumumkan hal
ini, ruang seminar utama di Fermilab benar2 penuh. Saking penuhnya, pas
direktur Pier Oddone dan deputy direktur Young-Kee Kim datang, semua
kursi sudah diklaim, dan mereka terpaksa duduk di lantai ;).

-- Haryo

Thanks Haryo atas informasinya.

Walaupun single top quark ini belum 5 sigma observation tapi sudah
merupakan hal terbaik/terbaru for looking for a New Physics
and Higgs mass limit.

Kapan Bs-Bsbar mixing result from D0 comes out ?
Ini akan sangat baik sebagai confirmasi on
CDF observation of Bs-Bsbar mixing.

] Kelanjutan dari berita single top quark
]
] http://www.fnal.gov/pub/presspass/press_releases/Single-Top.html
]
] Sekedar selingan: Hari Jum'at lalu waktu seminar yang mengumumkan hal
] ini, ruang seminar utama di Fermilab benar2 penuh. Saking penuhnya, pas
] direktur Pier Oddone dan deputy direktur Young-Kee Kim datang, semua
] kursi sudah diklaim, dan mereka terpaksa duduk di lantai ;).

Ini menunjukan bahwa director and deputynya adalah orang yang rendah hati.
Tapi memang ini kesalahan mereka kenapa datang terlambat.

------------------------------------------------------------------------------
\\
Paper: hep-ex/0612052
Date: Thu, 21 Dec 2006 20:25:02 GMT (229kb)

Title: Evidence for production of single top quarks and first direct
measurement of |Vtb|
Authors: D0 Collaboration, V.M. Abazov, et al
Categories: hep-ex
Comments: Submitted to Physical Review Letters
Report-no: FERMILAB-PUB-06/475-E
\\
The D0 Collaboration presents first evidence for the production of single top
quarks at the Fermilab Tevatron ppbar collider. Using a 0.9 fb^-1 dataset, we
apply a multivariate analysis to separate signal from background and measure
sigma(ppbar-]tb+X,tqb+X) = 4.9 +- 1.4 pb. The probability to measure a cross
section at this value or higher in the absence of signal is 0.035

xxx

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