Event shapes in deep inelastic scattering at HERA.

The ZEUS collaboration Chekanov, S. ; Derrick, M. ; Magill, S. ; et al.
Nucl.Phys.B 767 (2007) 1-28, 2007.
Inspire Record 714503 DOI 10.17182/hepdata.11818

Mean values and differential distributions of event-shape variables have been studied in neutral current deep inelastic scattering using an integrated {luminosity} of 82.2 pb$^{-1}$ collected with the ZEUS detector at HERA. The kinematic range was $80 < Q^2 < 20 480\gev^2$ and $0.0024 < x < 0.6$, where $Q^2$ is the virtuality of the exchanged boson and $x$ is the Bjorken variable. The data are compared with a model based on a combination of next-to-leading-order QCD calculations with next-to-leading-logarithm corrections and the Dokshitzer-Webber non-perturbative power corrections. The power-correction method provides a reasonable description of the data for all event-shape variables studied. Nevertheless, the lack of consistency of the determination of $\alpha_s$ and of the non-perturbative parameter of the model, $\albar$, suggests the importance of higher-order processes that are not yet included in the model.

69 data tables

Mean value of the event shape variable 1-THRUST(C=T).

Mean value of the event shape variable B(C=T).

Mean value of the event shape variable RHO**2.

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Measurement of event shape variables in deep-inelastic scattering at HERA.

The H1 collaboration Aktas, A. ; Andreev, V. ; Anthonis, T. ; et al.
Eur.Phys.J.C 46 (2006) 343-356, 2006.
Inspire Record 699835 DOI 10.17182/hepdata.11377

Deep-inelastic ep scattering data taken with the H1 detector at HERA and corresponding to an integrated luminosity of 106 pb^{-1} are used to study the differential distributions of event shape variables. These include thrust, jet broadening, jet mass and the C-parameter. The four-momentum transfer Q is taken to be the relevant energy scale and ranges between 14 GeV and 200 GeV. The event shape distributions are compared with perturbative QCD predictions, which include resummed contributions and analytical power law corrections, the latter accounting for non-perturbative hadronisation effects. The data clearly exhibit the running of the strong coupling alpha_s(Q) and are consistent with a universal power correction parameter alpha_0 for all event shape variables. A combined QCD fit using all event shape variables yields alpha_s(mZ) = 0.1198 \pm 0.0013 ^{+0.0056}_{-0.0043} and alpha_0 = 0.476 \pm 0.008 ^{+0.018} _{-0.059}.

71 data tables

Normalised distribution of (1-THRUST) where THRUST is w.r.t the axis which maximises the sum of the longitudinal momenta in the current hemisphere, for Q = 14.0 to 16.0 GeV and X = 0.00841 .

Normalised distribution of (1-THRUST) where THRUST is w.r.t the axis which maximises the sum of the longitudinal momenta in the current hemisphere, for Q = 16.0 to 20.0 GeV and X = 0.01180 .

Normalised distribution of (1-THRUST) where THRUST is w.r.t the axis which maximises the sum of the longitudinal momenta in the current hemisphere, for Q = 20.0 to 30.0 GeV and X = 0.02090 .

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Measurement of event shape variables in deep inelastic e p scattering.

The H1 collaboration Adloff, C. ; Aid, S. ; Anderson, M. ; et al.
Phys.Lett.B 406 (1997) 256-270, 1997.
Inspire Record 443753 DOI 10.17182/hepdata.23948

Deep inelastic e^+ scattering data, taken with the H1 detector at HERA, are used to study the event shape variables thrust, jet broadening and jet mass in the current hemisphere of the Breit frame over a large range of momentum transfers Q between 7 GeV and 100 GeV. The data are compared with results from e^+e^- experiments. Using second order QCD calculations and an approach to relate hadronisation effects to power corrections an analysis of the Q dependences of the means of the event shape parameters is presented, from which both the power corrections and the strong coupling constant are determined without any assumption on fragmentation models. The power corrections of all event shape variables investigated follow a 1/Q behaviour and can be described by a common parameter alpha_0.

6 data tables

The data on the differential event shape distrubutions are shown only as a illustration to show the agreement with the Lepto and pQCD calculations and contain only statistical errors. The authors are preparing another paper which details these differential distributions including full point-to-point systematics.

Usual definition of Thrust.

The same as usual thrust definition but with the thrust axis replaced by the current hemisphere axis (0,0,-1), where positive Z direction coincide with theincoming proton beam direction.

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