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43
result(s) for
"Ravdandorj, T."
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Determination of the strong coupling constant αs(mZ) in next-to-next-to-leading order QCD using H1 jet cross section measurements
The strong coupling constant
α
s
is determined from inclusive jet and dijet cross sections in neutral-current deep-inelastic
ep
scattering (DIS) measured at HERA by the H1 collaboration using next-to-next-to-leading order (NNLO) QCD predictions. The dependence of the NNLO predictions and of the resulting value of
α
s
(
m
Z
)
at the
Z
-boson mass
m
Z
are studied as a function of the choice of the renormalisation and factorisation scales. Using inclusive jet and dijet data together, the strong coupling constant is determined to be
α
s
(
m
Z
)
=
0.1157
(
20
)
exp
(
29
)
th
. Complementary,
α
s
(
m
Z
)
is determined together with parton distribution functions of the proton (PDFs) from jet and inclusive DIS data measured by the H1 experiment. The value
α
s
(
m
Z
)
=
0.1142
(
28
)
tot
obtained is consistent with the determination from jet data alone. The impact of the jet data on the PDFs is studied. The running of the strong coupling is tested at different values of the renormalisation scale and the results are found to be in agreement with expectations.
Journal Article
Measurement of jet production cross sections in deep-inelastic ep scattering at HERA
A precision measurement of jet cross sections in neutral current deep-inelastic scattering for photon virtualities
5.5
<
Q
2
<
80
GeV
2
and inelasticities
0.2
<
y
<
0.6
is presented, using data taken with the H1 detector at HERA, corresponding to an integrated luminosity of
290
pb
-
1
. Double-differential inclusive jet, dijet and trijet cross sections are measured simultaneously and are presented as a function of jet transverse momentum observables and as a function of
Q
2
. Jet cross sections normalised to the inclusive neutral current DIS cross section in the respective
Q
2
-interval are also determined. Previous results of inclusive jet cross sections in the range
150
<
Q
2
<
15
,
000
GeV
2
are extended to low transverse jet momenta
5
<
P
T
jet
<
7
GeV
. The data are compared to predictions from perturbative QCD in next-to-leading order in the strong coupling, in approximate next-to-next-to-leading order and in full next-to-next-to-leading order. Using also the recently published H1 jet data at high values of
Q
2
, the strong coupling constant
α
s
(
M
Z
)
is determined in next-to-leading order.
Journal Article
Measurement of groomed event shape observables in deep-inelastic electron-proton scattering at HERA
The H1 Collaboration at HERA reports the first measurement of groomed event shape observables in deep inelastic electron-proton scattering (DIS) at
s
=
319
GeV, using data recorded between the years 2003 and 2007 with an integrated luminosity of 351
pb
-
1
. Event shapes provide incisive probes of perturbative and non-perturbative QCD. Grooming techniques have been used for jet measurements in hadronic collisions; this paper presents the first application of grooming to DIS data. The analysis is carried out in the Breit frame, utilizing the novel Centauro jet clustering algorithm that is designed for DIS event topologies. Events are required to have squared momentum-transfer
Q
2
>
150
GeV
2
and inelasticity
0.2
<
y
<
0.7
. We report measurements of the production cross section of groomed event 1-jettiness and groomed invariant mass for several choices of grooming parameter. Monte Carlo model calculations and analytic calculations based on Soft Collinear Effective Theory are compared to the measurements.
Journal Article
Measurement of exclusive π+π- and ρ0 meson photoproduction at HERA
Exclusive photoproduction of
ρ
0
(
770
)
mesons is studied using the H1 detector at the
ep
collider HERA. A sample of about 900,000 events is used to measure single- and double-differential cross sections for the reaction
γ
p
→
π
+
π
-
Y
. Reactions where the proton stays intact (
m
Y
=
m
p
) are statistically separated from those where the proton dissociates to a low-mass hadronic system (
m
p
<
m
Y
<
10
GeV
). The double-differential cross sections are measured as a function of the invariant mass
m
π
π
of the decay pions and the squared 4-momentum transfer
t
at the proton vertex. The measurements are presented in various bins of the photon–proton collision energy
W
γ
p
. The phase space restrictions are
0.5
≤
m
π
π
≤
2.2
GeV
,
|
t
|
≤
1.5
GeV
2
, and
20
≤
W
γ
p
≤
80
GeV
. Cross section measurements are presented for both elastic and proton-dissociative scattering. The observed cross section dependencies are described by analytic functions. Parametrising the
m
π
π
dependence with resonant and non-resonant contributions added at the amplitude level leads to a measurement of the
ρ
0
(
770
)
meson mass and width at
m
ρ
=
770.8
-
2.7
+
2.6
(
tot.
)
MeV
and
Γ
ρ
=
151.3
-
3.6
+
2.7
(
tot.
)
MeV
, respectively. The model is used to extract the
ρ
0
(
770
)
contribution to the
π
+
π
-
cross sections and measure it as a function of
t
and
W
γ
p
. In a Regge asymptotic limit in which one Regge trajectory
α
(
t
)
dominates, the intercept
α
(
t
=
0
)
=
1.0654
-
0.0067
+
0.0098
(
tot.
)
and the slope
α
′
(
t
=
0
)
=
0.233
-
0.074
+
0.067
(
tot.
)
GeV
-
2
of the
t
dependence are extracted for the case
m
Y
=
m
p
.
Journal Article
Inclusive deep inelastic scattering at high Q(2) with longitudinally polarised lepton beams at HERA
Inclusive e(+/-)p single and double differential cross sections for neutral and charged current deep inelastic scattering processes are measured with the H1 detector at HERA. The data were taken at a centre-of-mass energy of root s = 319 GeV with a total integrated luminosity of 333.7 pb(-1) shared between two lepton beam charges and two longitudinal lepton polarisation modes. The differential cross sections are measured in the range of negative four-momentum transfer squared, Q(2), between 60 and 50 000GeV(2), and Bjorken x between 0.0008 and 0.65. The measurements are combined with earlier published unpolarised H1 data to improve statistical precision and used to determine the structure function xF(3)(gamma Z). A measurement of the neutral current parity violating structure function F-2(gamma Z) is presented for the first time. The polarisation dependence of the charged current total cross section is also measured. The new measurements are well described by a next-to-leading order QCD fit based on all published H1 inclusive cross section data which are used to extract the parton distribution functions of the proton.
Journal Article
Measurement of the inclusive ep scattering cross section at low Q (2) and x at HERA
A measurement of the inclusive ep scattering cross section is presented in the region of low momentum transfers, 0.2 GeV2 a parts per thousand currency signQ (2)a parts per thousand currency sign12 GeV2, and low Bjorken x, 5a <...10(-6)a parts per thousand currency signxa parts per thousand currency sign0.02. The result is based on two data sets collected in dedicated runs by the H1 Collaboration at HERA at beam energies of 27.6 GeV and 920 GeV for positrons and protons, respectively. A combination with data previously published by H1 leads to a cross section measurement of a few percent accuracy. A kinematic reconstruction method exploiting radiative ep events extends the measurement to lower Q (2) and larger x. The data are compared with theoretical models which apply to the transition region from photoproduction to deep inelastic scattering.
Journal Article
Diffractive dijet production with a leading proton in ep collisions at HERA
A
bstract
The cross section of the diffractive process
e
+
p
→
e
+
Xp
is measured at a centre-of-mass energy of 318 GeV, where the system
X
contains at least two jets and the leading final state proton
p
is detected in the H1 Very Forward Proton Spectrometer. The measurement is performed in photoproduction with photon virtualities
Q
2
<
2 GeV
2
and in deep-inelastic scattering with 4 GeV
2
< Q
2
<
80 GeV
2
. The results are compared to next- to-leading order QCD calculations based on diffractive parton distribution functions as extracted from measurements of inclusive cross sections in diffractive deep-inelastic scattering.
Journal Article
Measurement of exclusive π+π- and ρ0 meson photoproduction at HERA
Exclusive photoproduction of ρ0(770) mesons is studied using the H1 detector at the ep collider HERA. A sample of about 900,000 events is used to measure single- and double-differential cross sections for the reaction γp→π+π-Y. Reactions where the proton stays intact (mY=mp) are statistically separated from those where the proton dissociates to a low-mass hadronic system (mp
Journal Article
Measurement of exclusive$${\\varvec{{{{\\pi ^+\\pi ^-}}}}}$$and$${\\varvec{{{{\\rho ^0}}}}}$$meson photoproduction at HERA
Exclusive photoproduction of$${{\\rho ^0}} (770)$$ρ 0 ( 770 ) mesons is studied using the H1 detector at the ep collider HERA. A sample of about 900,000 events is used to measure single- and double-differential cross sections for the reaction$$\\gamma p \\rightarrow \\pi ^{+}\\pi ^{-}Y$$γ p → π + π - Y . Reactions where the proton stays intact ($${{{m_Y}} {=}m_p}$$m Y = m p ) are statistically separated from those where the proton dissociates to a low-mass hadronic system ($$m_p{<}{{m_Y}} {<}10~{{\\text {GeV}}} $$m p < m Y < 10 GeV ). The double-differential cross sections are measured as a function of the invariant mass$$m_{\\pi \\pi }$$m π π of the decay pions and the squared 4-momentum transfer t at the proton vertex. The measurements are presented in various bins of the photon–proton collision energy$${{W_{\\gamma p}}} $$W γ p . The phase space restrictions are$$0.5\\le m_{\\pi \\pi } \\le 2.2~{{\\text {GeV}}} $$0.5 ≤ m π π ≤ 2.2 GeV ,$$\\vert t\\vert \\le 1.5~{{\\text {GeV}^2}} $$| t | ≤ 1.5 GeV 2 , and$$20 \\le W_{\\gamma p} \\le 80~{{\\text {GeV}}} $$20 ≤ W γ p ≤ 80 GeV . Cross section measurements are presented for both elastic and proton-dissociative scattering. The observed cross section dependencies are described by analytic functions. Parametrising the$${m_{\\pi \\pi }}$$m π π dependence with resonant and non-resonant contributions added at the amplitude level leads to a measurement of the$${{\\rho ^0}} (770)$$ρ 0 ( 770 ) meson mass and width at$$m_\\rho = 770.8{}^{+2.6}_{-2.7}~({\\text {tot.}})~{{\\text {MeV}}} $$m ρ = 770.8 - 2.7 + 2.6 ( tot. ) MeV and$$\\Gamma _\\rho = 151.3 {}^{+2.7}_{-3.6}~({\\text {tot.}})~{{\\text {MeV}}} $$Γ ρ = 151.3 - 3.6 + 2.7 ( tot. ) MeV , respectively. The model is used to extract the$${{\\rho ^0}} (770)$$ρ 0 ( 770 ) contribution to the$$\\pi ^{+}\\pi ^{-}$$π + π - cross sections and measure it as a function of t and$${W_{\\gamma p}}$$W γ p . In a Regge asymptotic limit in which one Regge trajectory$$\\alpha (t)$$α ( t ) dominates, the intercept$$\\alpha (t{=}0) = 1.0654\\ {}^{+0.0098}_{-0.0067}~({\\text {tot.}})$$α ( t = 0 ) = 1.0654 - 0.0067 + 0.0098 ( tot. ) and the slope$$\\alpha ^\\prime (t{=}0) = 0.233 {}^{+0.067 }_{-0.074 }~({\\text {tot.}}) ~{{\\text {GeV}^{-2}}} $$α ′ ( t = 0 ) = 0.233 - 0.074 + 0.067 ( tot. ) GeV - 2 of the t dependence are extracted for the case$$m_Y{=}m_p$$m Y = m p .
Journal Article
Measurement of dijet production in diffractive deep-inelastic ep scattering at HERA
A
bstract
A measurement is presented of single- and double-differential dijet cross sections in diffractive deep-inelastic
ep
scattering at HERA using data collected by the H1 experiment corresponding to an integrated luminosity of 290 pb
−1
. The investigated phase space is spanned by the photon virtuality in the range of 4
< Q
2
<
100 GeV
2
and by the fractional proton longitudinal momentum loss
x
ℙ
<
0
.
03. The resulting cross sections are compared with next-to-leading order QCD predictions based on diffractive parton distribution functions and the value of the strong coupling constant is extracted.
Journal Article