A precision measurement of the mass of the top quark

The Standard Model of particle physics contains about two dozen parameters - such as particle masses - whose origins are still unknown and cannot be predicted, but whose values are constrained through their interactions. In particular, the masses of the top (t) quark (M_t) and W boson constrain the mass of the long-hypothesized, but thus far not observed, Higgs boson. A precise measurement of the top-quark mass can therefore point to where to look for the Higgs, and indeed whether the hypothesis of a SM Higgs is consistent with experimental data. Since top quarks are produced in pairs and decay in only ~10^-24 s into various final states, reconstructing their mass from their decay products is very challenging. Here we report a technique that extracts far more information from each top-quark event and yields a greatly improved precision on the top mass of 5.3 GeV/c^2, compared to previous measurements. When our new result is combined with our published measurement in a complementary decay mode and with the only other measurements available, the new world average for M_t becomes 178.0 +- 4.3 GeV/c^2. As a result, the most likely Higgs mass increases from the experimentally excluded value of 96 GeV/c^2 to 117 GeV/c^2, which is beyond current experimental sensitivity. The upper limit on the Higgs mass at 95% confidence level is raised from 219 GeV/c^2 to 251 GeV/c^2.

Note:

For high-resolution version of figures, the article, as appeared in Nature, and related News & Views, see http://www-d0.fnal.gov/Run2Physics/top/public/public.html (8 pages, 4 color figures)

D0
anti-p p: colliding beams
anti-p p: inclusive reaction
top: pair production
mass: top
top: decay
final state: ((n)jet lepton)
data analysis method
statistical analysis
DZERO

References(23)

Figures(4)

Review of particle physics. Particle Data Group

et al.

- Phys.Rev.D 66 (2002) 010001
•
DOI:
- 10.1103/PhysRevD.66.010001

Measurement of the Top Quark Mass with the Collider Detector at Fermilab

CDF

Collaboration

•

T. Affolder
(
- LBL, Berkeley
)

et al.

- Phys.Rev.D 63 (2001) 032003
•
e-Print:
- hep-ex/0006028
•
DOI:
- 10.1103/PhysRevD.63.032003

Measurement of the Top Quark Mass in the Dilepton Channel

D0

Collaboration

•

B. Abbott
(
- New York U.
)

et al.

- Phys.Rev.D 60 (1999) 052001
•
e-Print:
- hep-ex/9808029
•
DOI:
- 10.1103/PhysRevD.60.052001

Combination of CDF and D0 results on the top-quark mass

CDF and
D0

Collaborations

•

P. Azzi

et al.

e-Print:
- hep-ex/0404010

Search for the standard model Higgs boson at LEP

LEP Working Group for Higgs boson searches and
ALEPH and
DELPHI and
L3 and
OPAL

Collaborations

•

R. Barate

et al.

- Phys.Lett.B 565 (2003) 61-75
•
e-Print:
- hep-ex/0306033
•
DOI:
- 10.1016/S0370-2693(03)00614-2

A Combination of preliminary electroweak measurements and constraints on the standard model

LEP and
ALEPH and
DELPHI and
L3 and
OPAL

Collaborations

•

the SLD Electroweak

for the collaborations.

e-Print:
- hep-ex/0312023

Observation of top quark production in $\bar{p}p$ collisions

CDF

Collaboration

•

F. Abe
(
- KEK, Tsukuba
)

et al.

- Phys.Rev.Lett. 74 (1995) 2626-2631
•
e-Print:
- hep-ex/9503002
•
DOI:
- 10.1103/PhysRevLett.74.2626

Observation of the top quark

D0

Collaboration

•

S. Abachi
(
- Fermilab
)

et al.

- Phys.Rev.Lett. 74 (1995) 2632-2637
•
e-Print:
- hep-ex/9503003
•
DOI:
- 10.1103/PhysRevLett.74.2632

The 115-GeV Higgs odyssey

John R. Ellis
(
- CERN
)

- Comments Nucl.Part.Phys. 2 (2002) A89-A103,
- CMS Bull. 04 (2000) 7-11
•
e-Print:
- hep-ex/0011086

Electroweak data and the Higgs boson mass: A Case for new physics

Michael S. Chanowitz
(
- LBL, Berkeley
)

- Phys.Rev.D 66 (2002) 073002
•
e-Print:
- hep-ph/0207123
•
DOI:
- 10.1103/PhysRevD.66.073002

Searches for the neutral Higgs bosons of the MSSM: Preliminary combined results using LEP data collected at energies up to 209-GeV

ALEPH and
DELPHI and
L3 and
OPAL

Collaborations

e-Print:
- hep-ex/0107030

Towards high precision predictions for the MSSM Higgs sector

G. Degrassi
(
- Rome III U. and
- INFN, Rome3
)
,
S. Heinemeyer
(
- Munich U.
)
,
W. Hollik
(
- Munich, Max Planck Inst.
)
,
P. Slavich
(
- Munich, Max Planck Inst. and
- Karlsruhe U., TTP
)
,
G. Weiglein
(
- Durham U., IPPP
)

- Eur.Phys.J.C 28 (2003) 133-143
•
e-Print:
- hep-ph/0212020
•
DOI:
- 10.1140/epjc/s2003-01152-2

Direct measurement of the top quark mass at D0

D0

Collaboration

•

B. Abbott
(
- New York U.
)

et al.

- Phys.Rev.D 58 (1998) 052001
•
e-Print:
- hep-ex/9801025
•
DOI:
- 10.1103/PhysRevD.58.052001

$t \bar{t}$ Production Cross Section in $p \bar{p}$ Collisions at $\sqrt{s}$ = 1.8-TeV

D0

Collaboration

•

V.M. Abazov
(
- Dubna, JINR
)

et al.

- Phys.Rev.D 67 (2003) 012004
•
e-Print:
- hep-ex/0205019
•
DOI:
- 10.1103/PhysRevD.67.012004

The D0 Detector

D0

Collaboration

•

S. Abachi

et al.

- Nucl.Instrum.Meth.A 338 (1994) 185-253
•
DOI:
- 10.1016/0168-9002(94)91312-9

Test of analysis method for top-antitop production and decay events

R.H. Dalitz
(
- Oxford U.
)
,
Gary R. Goldstein
(
- Tufts U.
)

- Proc.Roy.Soc.Lond.A 455 (1999) 2803-2834
•
e-Print:
- hep-ph/9802249
•
DOI:
- 10.1098/rspa.1999.0428

Dynamical likelihood method for reconstruction of events with missing momentum. 3: Analysis of a CDF high p(T) e mu event as t anti-t production

- J.Phys.Soc.Jap. 62 (1993) 1177-1182
•
DOI:
- 10.1143/JPSJ.62.1177

On the determination of M(W) and TGCs in W pair production using the best measured kinematical variables

Frits A. Berends
(
- CERN and
- Leiden U.
)
,
C.G. Papadopoulos
(
- Democritos Nucl. Res. Ctr.
)
,
R. Pittau
(
- PSI, Villigen
)

- Phys.Lett.B 417 (1998) 385-389
•
e-Print:
- hep-ph/9709257
•
DOI:
- 10.1016/S0370-2693(97)01374-9

Measurement of the W pair cross-section and of the W mass in e+ e- interactions at 172-GeV

DELPHI

Collaboration

•

P. Abreu

et al.

- Eur.Phys.J.C 2 (1998) 581-595
•
DOI:
- 10.1007/s100520050163

HERWIG: A Monte Carlo event generator for simulating hadron emission reactions with interfering gluons. Version 5.1 - April 1991

G. Marchesini
(
- Parma U. and
- INFN, Parma
)
,
B.R. Webber
(
- Cambridge U.
)
,
G. Abbiendi
(
- Padua U. and
- INFN, Padua
)
,
I.G. Knowles
(
- Glasgow U.
)
,
M.H. Seymour
(
- Cambridge U.
)

et al.

- Comput.Phys.Commun. 67 (1992) 465-508,
- Comput. Phys. Commun. 67 (1992) 465-508 and Hamburg DESY - DESY 91-048 (91/05,rec.Jul.) 49 p
•
DOI:
- 10.1016/0010-4655(92)90055-4

Angular correlations in top quark pair production and decay at hadron colliders

Gregory Mahlon
(
- Michigan U.
)
,
Stephen J. Parke
(
- Fermilab
)

- Phys.Rev.D 53 (1996) 4886-4896
•
e-Print:
- hep-ph/9512264
•
DOI:
- 10.1103/PhysRevD.53.4886

Global QCD Analysis and the CTEQ Parton Distributions

H.L. Lai
(
- Michigan State U.
)
,
J. Botts
(
- Michigan State U. and
- DESY, Zeuthen
)
,
J. Huston
(
- Michigan State U.
)
,
J.G. Morfin
(
- Fermilab
)
,
J.F. Owens
(
- Florida State U.
)