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<mY<10GeV). The double-differential cross sections are measured as a function of the invariant mass mππ 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 Wγp. The phase space restrictions are 0.5≤mππ≤2.2GeV, |t|≤1.5GeV2, and 20≤Wγp≤80GeV. Cross section measurements are presented for both elastic and proton-dissociative scattering. The observed cross section dependencies are described by analytic functions. Parametrising the mππ dependence with resonant and non-resonant contributions added at the amplitude level leads to a measurement of the ρ0(770) meson mass and width at mρ=770.8-2.7+2.6(tot.)MeV and Γρ=151.3-3.6+2.7(tot.)MeV, respectively. The model is used to extract the ρ0(770) contribution to the π+π- cross sections and measure it as a function of t and Wγp. 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 mY=mp.
Full text
Available for:
DOBA, IZUM, KILJ, NUK, PILJ, PNG, SAZU, SIK, UILJ, UKNU, UL, UM, UPUK
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.
Abstract 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 .
Full text
Available for:
DOBA, IZUM, KILJ, NUK, PILJ, PNG, SAZU, SIK, UILJ, UKNU, UL, UM, UPUK
A measurement is presented of elastic deeply virtual Compton scattering \(\gamma^* p \rightarrow {\ensuremath{\gamma}} p\) made using e + p collision data corresponding to a luminosity of 46.5 pb-1, ...taken with the H1 detector at HERA. The cross section is measured as a function of the photon virtuality, Q 2, the invariant mass of the p system, W, and for the first time, differentially in the squared momentum transfer at the proton vertex, t, in the kinematic range \(2 < Q^{ 2} < 80 {\rm GeV}^2\), \(30 < W < 140 {\rm GeV}\) and \(\vert t\vert < 1 {\rm GeV}^2\). QCD based calculations at next-to-leading order using generalized parton distributions can describe the data, as can colour dipole model predictions.
Full text
Available for:
DOBA, FZAB, GEOZS, IJS, IMTLJ, IZUM, KILJ, KISLJ, NUK, OILJ, PILJ, PNG, SAZU, SBCE, SBJE, SBMB, SIK, UILJ, UKNU, UL, UM, UPUK, VKSCE, ZAGLJ
The cross section for the diffractive deep-inelastic scattering process ep→eXp is measured, with the leading final state proton detected in the H1 Forward Proton Spectrometer. The data analysed cover ...the range xIP<0.1 in fractional proton longitudinal momentum loss, 0.08<|t|<0.5 GeV-2 in squared four-momentum transfer at the proton vertex, 2<Q2<50 GeV2 in photon virtuality and 0.004<β=x/xIP<1, where x is the Bjorken scaling variable. For , the differential cross section has a dependence of approximately dσ/dt∝e6t, independently of xIP, β and Q2 within uncertainties. The cross section is also measured triple differentially in xIP, β and Q2. The xIP dependence is interpreted in terms of an effective pomeron trajectory with intercept αIP(0)=1.114±0.018(stat.)±0.012(syst.)+0.040-0.020(model) and a sub-leading exchange. The data are in good agreement with an H1 measurement for which the event selection is based on a large gap in the rapidity distribution of the final state hadrons, after accounting for proton dissociation contributions in the latter. Within uncertainties, the dependence of the cross section on x and Q2 can thus be factorised from the dependences on all studied variables which characterise the proton vertex, for both the pomeron and the sub-leading exchange.
Full text
Available for:
DOBA, FZAB, GEOZS, IJS, IMTLJ, IZUM, KILJ, KISLJ, NUK, OILJ, PILJ, PNG, SAZU, SBCE, SBJE, SBMB, SIK, UILJ, UKNU, UL, UM, UPUK, VKSCE, ZAGLJ
The cross section of diffractive deep-inelastic scattering
ep
→
eXp
is measured, where the system
X
contains at least two jets and the leading final state proton is detected in the H1 Forward Proton ...Spectrometer. The measurement is performed for fractional proton longitudinal momentum loss
x
ℙ
<0.1 and covers the range 0.1<|
t
|<0.7 GeV
2
in squared four-momentum transfer at the proton vertex and 4<
Q
2
<110 GeV
2
in photon virtuality. The differential cross sections extrapolated to |
t
|<1 GeV
2
are in agreement with next-to-leading order QCD predictions based on diffractive parton distribution functions extracted from measurements of inclusive and dijet cross sections in diffractive deep-inelastic scattering. The data are also compared with leading order Monte Carlo models.
Full text
Available for:
DOBA, FZAB, GEOZS, IJS, IMTLJ, IZUM, KILJ, KISLJ, NUK, OILJ, PILJ, PNG, SAZU, SBCE, SBJE, SBMB, SIK, UILJ, UKNU, UL, UM, UPUK, VKSCE, ZAGLJ
A search for first generation scalar and vector leptoquarks produced in ep collisions is performed by the H1 experiment at HERA. The full H1 data sample is used in the analysis, corresponding to an ...integrated luminosity of 446 pb−1. No evidence for the production of leptoquarks is observed in final states with a large transverse momentum electron or with large missing transverse momentum, and constraints on leptoquark models are derived. For leptoquark couplings of electromagnetic strength λ=0.3, first generation leptoquarks with masses up to 800 GeV are excluded at 95% confidence level.
Full text
Available for:
GEOZS, IJS, IMTLJ, KILJ, KISLJ, NUK, OILJ, SAZU, SBCE, UL, UM, UPCLJ, UPUK
A measurement is presented of inelastic photo- and electroproduction of
J
/
ψ
mesons in
ep
scattering at HERA. The data were recorded with the H1 detector in the period from 2004 to 2007. Single and ...double differential cross sections are determined and the helicity distributions of the
J
/
ψ
mesons are analysed. The results are compared to theoretical predictions in the colour singlet model and in the framework of non-relativistic QCD. Calculations in the colour singlet model using a
k
T
factorisation ansatz are able to give a good description of the data, while colour singlet model calculations to next-to-leading order in collinear factorisation underestimate the data.
Full text
Available for:
DOBA, FZAB, GEOZS, IJS, IMTLJ, IZUM, KILJ, KISLJ, NUK, OILJ, PILJ, PNG, SAZU, SBCE, SBJE, SBMB, SIK, UILJ, UKNU, UL, UM, UPUK, VKSCE, ZAGLJ
P-Glycoprotein, the plasma membrane protein responsible for the multidrug resistance of some tumour cells, is an active transporter of a number of structurally unrelated hydrophobic drugs. We have ...characterized the modulation of its ATPase activity by a multidrug-resistance-related cytotoxic drug, vinblastine, and different multidrug-resistance-reversing agents, verapamil and the dihydropyridines nicardipine, nimodipine, nitrendipine, nifedipine and azidopine. P-Glycoprotein ATPase activity was measured by using native membrane vesicles containing large amounts of P-glycoprotein, prepared from the highly multidrug-resistant lung fibroblasts DC-3F/ADX. P-Glycoprotein ATPase is activated by verapamil and by nicardipine but not by vinblastine. Among the five dihydropyridines tested, the higher the hydrophobicity, the higher was the activation factor with respect to the basal activity and the lower was the half-maximal activating concentration. The vinblastine-specific binding on P-glycoprotein is reported by the inhibitions of the verapamil- and the nicardipine-stimulated ATPase. These inhibitions are purely competitive, which means that the bindings of vinblastine and verapamil, or vinblastine and nicardipine, on P-glycoprotein are mutually exclusive. In contrast, verapamil and nicardipine display mutually non-competitive interactions. This demonstrates the existence of two distinct specific sites for these two P-glycoprotein modulators on which they can bind simultaneously and separately to the vinblastine site. The nicardipine-stimulated ATPase activity in the presence of the other dihydropyridines shows mixed-type inhibitions. These dihydropyridines have thus different binding sites that interact mutually to decrease their respective, separately determined affinities. This could be due to steric constraints between sites close to each other. This is supported by the observation that vinblastine binding is not mutually exclusive with nifedipine or nitrendipine binding, whereas it is mutually exclusive with nicardipine. Moreover, verapamil binding also interacts with the five dihydropyridines by mixed inhibitions, with different destabilization factors. On the whole our enzymic data show that P-glycoprotein has distinct but interacting binding sites for various modulators of its ATPase function.
Measurements of
D
∗
(
2010
)
meson production in diffractive deep inelastic scattering
(
5
<
Q
2
<
100
GeV
2
)
are presented which are based on HERA data recorded at a centre-of-mass energy
s
=
319
...GeV
with an integrated luminosity of 287 pb
-
1
. The reaction
e
p
→
e
X
Y
is studied, where the system
X
, containing at least one
D
∗
(
2010
)
meson, is separated from a leading low-mass proton dissociative system
Y
by a large rapidity gap. The kinematics of
D
∗
candidates are reconstructed in the
D
∗
→
K
π
π
decay channel. The measured cross sections compare favourably with next-to-leading order QCD predictions, where charm quarks are produced via boson-gluon fusion. The charm quarks are then independently fragmented to the
D
∗
mesons. The calculations rely on the collinear factorisation theorem and are based on diffractive parton densities previously obtained by H1 from fits to inclusive diffractive cross sections. The data are further used to determine the diffractive to inclusive
D
∗
production ratio in deep inelastic scattering.
Full text
Available for:
DOBA, IZUM, KILJ, NUK, PILJ, PNG, SAZU, SIK, UILJ, UKNU, UL, UM, UPUK
PDF
