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Dijet production in diffractive deep inelastic scattering at HERA

The ZEUS collaboration Chekanov, S. ; Derrick, M. ; Magill, S. ; et al.
Eur.Phys.J. C52 (2007) 813-832, 2007.
Inspire Record 757973 DOI 10.17182/hepdata.45428

The production of dijets in diffractive deep inelastic scattering has been measured with the ZEUS detector at HERA using an integrated luminosity of $61 \pbi$. The dijet cross section has been measured for virtualities of the exchanged virtual photon, $5 < Q^2 < 100 \gev^2$, and $\gamma^{*} p$ centre-of-mass energies, 100 < W < 250 GeV. The jets, identified using the inclusive k_{T} algorithm in the $\gamma^* p$ frame, were required to have a transverse energy $E^*_{T, \rm jet} > 4 \gev$ and the jet with the highest transverse energy was required to have $E^*_{T,\rm jet} > 5 \gev$. All jets were required to be in the pseudorapidity range $-3.5 < \eta^*_{\rm jet} < 0$. The differential cross sections are compared to leading-order predictions and next-to-leading-order QCD calculations based on recent diffractive parton densities extracted from inclusive diffractive deep inelastic scattering data.

17 data tables

Total di-jet cross section SIG as a function of Q**2 .

Distribution of D(SIG)/DQ**2 as a function of Q**2 .

Distribution of D(SIG)/DW as a function of W .

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The Dependence of dijet production on photon virtuality in ep collisions at HERA

The ZEUS collaboration Chekanov, S. ; Derrick, M. ; Loizides, J.H. ; et al.
Eur.Phys.J. C35 (2004) 487-500, 2004.
Inspire Record 649041 DOI 10.17182/hepdata.46279

The dependence of dijet production on the virtuality of the exchanged photon, Q^2, has been studied by measuring dijet cross sections in the range 0 < Q^2 < 2000 GeV^2 with the ZEUS detector at HERA using an integrated luminosity of 38.6 pb^-1. Dijet cross sections were measured for jets with transverse energy E_T^jet > 7.5 and 6.5 GeV and pseudorapidities in the photon-proton centre-of-mass frame in the range -3 < eta^jet <0. The variable xg^obs, a measure of the photon momentum entering the hard process, was used to enhance the sensitivity of the measurement to the photon structure. The Q^2 dependence of the ratio of low- to high-xg^obs events was measured. Next-to-leading-order QCD predictions were found to generally underestimate the low-xg^obs contribution relative to that at high xg^obs. Monte Carlo models based on leading-logarithmic parton-showers, using a partonic structure for the photon which falls smoothly with increasing Q^2, provide a qualitative description of the data.

19 data tables

The measured dijet DSIG/DQ**2 distributions.

Measured dijet cross sections as a function of Q**2 in two regions of X(C=GAMMA).

The measured dijet DSIG/DQ**2/DET distributions. Here ET(P=4) is the transverse energy of the highest transverse energy jet.

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Measurement of dijet production at low Q**2 at HERA

The H1 collaboration Aktas, A. ; Andreev, V. ; Anthonis, T. ; et al.
Eur.Phys.J. C37 (2004) 141-159, 2004.
Inspire Record 642523 DOI 10.17182/hepdata.46280

Triple differential dijet cross sections in e^\pm p interactions are presented in the region of photon virtualities 2<Q^2<80GeV^2, inelasticities 0.1<y<0.85, jet transverse energies E_T1>7GeV, E_T2>5GeV, and pseudorapidities -2.5 < eta_1^*, eta_2^* <0. The measurements are made in the gamma^* p centre-of-mass frame, using an integrated luminosity of 57pb^-1. The data are compared with NLO QCD calculations and LO Monte Carlo programs with and without a resolved virtual photon contribution. NLO QCD calculations fail to describe the region of low Q^2 and low jet transverse energies, in contrast to a LO Monte Carlo generator which includes direct and resolved photon interactions with both transversely and longitudinally polarised photons. Initial and final state parton showers are tested as a mechanism for including higher order QCD effects in low E_T jet production.

16 data tables

Triple differential dijet cross sections as a function of Q**2, ET and X(C=GAMMA).

Triple differential dijet cross sections as a function of Q**2, ET and X(C=GAMMA).

Triple differential dijet cross sections as a function of Q**2, ET and X(C=GAMMA).

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Inclusive dijet production at low Bjorken x in deep inelastic scattering

The H1 collaboration Aktas, A. ; Andreev, V. ; Anthonis, T. ; et al.
Eur.Phys.J. C33 (2004) 477-493, 2004.
Inspire Record 630329 DOI 10.17182/hepdata.46329

Dijet production in deep inelastic ep scattering is investigated in the region of low values of the Bjorken-variable x (10^-4 &lt; x &lt; 10^-2) and low photon virtualities Q^2 (5 &lt; Q^2 &lt; 100 GeV^2). The measured dijet cross sections are compared with perturbative QCD calculations in next-to-leading order. For most dijet variables studied, these calculations can provide a reasonable description of the data over the full phase space region covered, including the region of very low x. However, large discrepancies are observed for events with small separation in azimuth between the two highest transverse momentum jets. This region of phase space is described better by predictions based on the CCFM evolution equation, which incorporates k_t factorized unintegrated parton distributions. A reasonable description is also obtained using the Color Dipole Model or models incorporating virtual photon structure.

15 data tables

Inclusive dijet cross section for a lower ET cut off of (5+0) GeV for the highest ET jet.

Inclusive dijet cross section for a lower ET cut off of (5+1) GeV for the highest ET jet.

Inclusive dijet cross section for a lower ET cut off of (5+2) GeV for the highest ET jet.

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Measurement of dijet cross-sections in photoproduction at HERA

The H1 collaboration Adloff, C. ; Andreev, V. ; Andrieu, B. ; et al.
Eur.Phys.J. C25 (2002) 13-23, 2002.
Inspire Record 581409 DOI 10.17182/hepdata.46764

Dijet cross sections as functions of several jet observables are measured in photoproduction using the H1 detector at HERA. The data sample comprises e^+p data with an integrated luminosity of 34.9 pb^(-1). Jets are selected using the inclusive k_T algorithm with a minimum transverse energy of 25 GeV for the leading jet. The phase space covers longitudinal proton momentum fraction x_p and photon longitudinal momentum fraction x_gamma in the ranges 0.05<x_p<0.6 and 0.1<x_gamma<1. The predictions of next-to-leading order perturbative QCD, including recent photon and proton parton densities, are found to be compatible with the data in a wide kinematical range.

10 data tables

Differential ep cross section for dijet production as a function of the invariant mass of the two jets.

Differential ep cross section for dijet production as a function of the average transverse energy the two jets.

Differential ep cross section for dijet production as a function of the maximum transverse energy the leading jet.

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Three Jet production in deep inelastic scattering at HERA

The H1 collaboration Adloff, C. ; Andreev, V. ; Andrieu, B. ; et al.
Phys.Lett. B515 (2001) 17-29, 2001.
Inspire Record 558699 DOI 10.17182/hepdata.46712

Three-jet production is studied for the first time in deep-inelastic positron-proton scattering. The measurement carried out with the H1 detector at HERA covers a large range of four-momentum transfer squared 5 < Q^2 < 5000 GeV^2 and invariant three-jet masses 25 < M_(3jet) < 140 GeV. Jets are defined by the inclusive k_T algorithm in the Breit frame. The size of the three-jet cross section and the ratio of the three-jet to the dijet cross section R_(3/2) are described over the whole phase space by the predictions of perturbative QCD in next-to-leading order. The shapes of angular jet distributions deviate significantly from a uniform population of the available phase space but are well described by the QCD calculation.

14 data tables

The inclusive 3-Jet cross section as a function of Q**2.

The ratio of 3 jets to 2 jets as a function of Q**2.

The inclusive 3-JET cross section as a function of Bjorken scaling variableX for the Q**2 range 5 to 100 GeV**2.

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Dijet production in charged and neutral current e+ p interactions at high Q**2

The H1 collaboration Adloff, C. ; Andreev, V. ; Andrieu, B. ; et al.
Eur.Phys.J. C19 (2001) 429-440, 2001.
Inspire Record 534736 DOI 10.17182/hepdata.46947

Jet production in charged and neutral current events in the kinematic range of Q^2 from 640 to 35000 GeV^2 is studied in deep-inelastic positron-proton scattering at HERA. The measured rate of multi-jet events and distributions of jet polar angle, transverse energy, dijet mass, and other dijet variables are presented. Using parton densities derived from inclusive DIS cross sections, perturbative QCD calculations in NLO are found to give a consistent description of both the neutral and charged current dijet production. A direct, model independent comparison of the jet distributions in charged and neutral current events confirms that the QCD dynamics of the hadronic final state is independent of the underlying electroweak scattering process.

9 data tables

Rates of charged current events as a function of Q**2.

Rates of neutral current events as a function of Q**2.

Normalised distribution in Y2 for NC and CC dijet events. Y2 is the smallest scaled value of KT (KTJET**2/W**2) given by the combination of (2+1) jets. The +1 refers to the proton remnant jet.

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Investigation of power corrections to event shape variables measured in deep inelastic scattering

The H1 collaboration Adloff, C. ; Andreev, V. ; Andrieu, B. ; et al.
Eur.Phys.J. C14 (2000) 255-269, 2000.
Inspire Record 512347 DOI 10.17182/hepdata.43865

Deep-inelastic ep scattering data, taken with the H1 detector at HERA, are used to study the event shape variables thrust, jet broadening, jet mass, C parameter and two kinds of differential two-jet rate. The data cover a large range of the four-momentum transfer Q, which is considered to be the relevant energy scale, between 7 GeV and 100 GeV. The Q dependences of the mean values are compared with second order calculations of perturbative QCD applying power law corrections proportional to 1/Q^p to account for hadronization effects. The concept of power corrections is investigated by fitting simultaneously a non-perturbative parameter alpha_p and the strong coupling constant alpha_s.

63 data tables

Corrected mean values of the (1-THRUST) distribution (w.r.t.current hemisphere axis) as a function of Q.

Corrected mean values of the Jet Broadenning (B) distribution (w.r.t.current hemisphere axis) as a function of Q.

Corrected mean values of the (1-THRUST) distribution (w.r.t.max long. momentum axis) as a function of Q.

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Measurement of Dijet photoproduction at high transverse energies at HERA

The ZEUS collaboration Breitweg, J. ; Chekanov, S. ; Derrick, M. ; et al.
Eur.Phys.J. C11 (1999) 35-50, 1999.
Inspire Record 500491 DOI 10.17182/hepdata.43992

The cross section for dijet photoproduction at high transverse energies is presented as a function of the transverse energies and the pseudorapidities of the jets. The measurement is performed using a sample of ep-interactions corresponding to an integrated luminosity of 6.3 pb^(-1), recorded by the ZEUS detector.Jets are defined by applying a k_T-clustering algorithm to the hadrons observed in the final state. The measured cross sections are compared to next-to-leading order QCD calculations. In a kinematic regime where theoretical uncertainties are expected to be small, the measured cross sections are higher than these calculations.

24 data tables

The dijet cross section for the full x(gamma) range as a function of the ET of the leading jet.

The dijet cross section for the full x(gamma) range as a function of the ET of the leading jet.

The dijet cross section for the full x(gamma) range as a function of the ET of the leading jet.

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Forward jet and particle production at HERA

The H1 collaboration Adloff, C. ; Anderson, M. ; Andreev, V. ; et al.
Nucl.Phys. B538 (1999) 3-22, 1999.
Inspire Record 476801 DOI 10.17182/hepdata.44172

Single particles and jets in deeply inelastic scattering at low x are measured with the H1 detector in the region away from the current jet and towards the proton remnant, known as the forward region. Hadronic final state measurements in this region are expected to be particularly sensitive to QCD evolution effects. Jet cross-sections are presented as a function of Bjorken-x for forward jets produced with a polar angle to the proton direction, theta, in the range 7 < theta < 20 degrees. Azimuthal correlations are studied between the forward jet and the scattered lepton. Charged and neutral single particle production in the forward region are measured as a function of Bjorken-x, in the range 5 < theta < 25 degrees, for particle transverse momenta larger than 1 GeV. QCD based Monte Carlo predictions and analytical calculations based on BFKL, CCFM and DGLAP evolution are compared to the data. Predictions based on the DGLAP approach fail to describe the data, except for those which allow for a resolved photon contribution.

2 data tables

Axis error includes +- 7/7 contribution (Dependence of the model used to correct the data).

Axis error includes +- 7/7 contribution (Dependence of the model used to correct the data).


Multijet event rates in deep inelastic scattering and determination of the strong coupling constant

The H1 collaboration Adloff, C. ; Anderson, M. ; Andreev, V. ; et al.
Eur.Phys.J. C6 (1999) 575-585, 1999.
Inspire Record 473521 DOI 10.17182/hepdata.44216

Jet event rates in deep inelastic ep scattering at HERA are investigated applying the modified JADE jet algorithm. The analysis uses data taken with the H1 detector in 1994 and 1995. The data are corrected for detector and hadronization effects and then compared with perturbative QCD predictions using next-to-leading order calculations. The strong coupling constant alpha_S(M_Z^2) is determined evaluating the jet event rates. Values of alpha_S(Q^2) are extracted in four different bins of the negative squared momentum transfer~$\qq$ in the range from 40 GeV2 to 4000 GeV2. A combined fit of the renormalization group equation to these several alpha_S(Q^2) values results in alpha_S(M_Z^2) = 0.117+-0.003(stat)+0.009-0.013(syst)+0.006(jet algorithm).

3 data tables

Measured (2+1) jet event rates using the modified JADE algorithm (C=MEAS), corrected to the hadron (C=HAD) and to the parton (C=PAR) level. The variable Z(p) is defined as the minimum (for i=1,2) of. (E_jet,i*(1-cos(theta_jet,i)/SUM(j=1,2)(E_jet,j*(1-cos(theta,j)).

ALPHAS at different Q2 values. The TOT error is the total error.

ALPHAS extrapolated to the Z0 mass. The second DSYS (systematic) error is from the jet finding alogrithm.


Dijet event rates in deep inelastic scattering at HERA

The H1 collaboration Adloff, C. ; Anderson, M. ; Andreev, V. ; et al.
Eur.Phys.J. C13 (2000) 415-426, 2000.
Inspire Record 472305 DOI 10.17182/hepdata.44322

Di-jet event rates have been measured for deep-inelastic scattering in the kinematic domain ~5 < Q^2 < ~100 GeV^2 and ~10^(-4) < x_Bj < ~10^(-2), and for jet transverse momenta squared p_t^2 > ~Q^2. The analysis is based on data collected with the H1 detector at HERA in 1994 corresponding to an integrated luminosity of about 2 pb^(-1). Jets are defined using a cone algorithm in the photon-proton centre of mass system requiring jet transverse momenta of at least 5 GeV. The di-jet event rates are shown as a function of Q^2 and x_Bj. Leading order models of point-like interacting photons fail to describe the data. Models which add resolved interacting photons or which implement the colour dipole model give a good description of the di-jet event rate. This is also the case for next-to-leading order calculations including contributions from direct and resolved photons.

4 data tables

Di-jet rates for 'Symmetric' and 'Asymmetric' scenarios for jet energy cuts.

Di-jet rates for 'Sum' scenario for jet energy cuts.

Di-jet rates for 'Symmetric' and 'Asymmetric' scenarios for jet energy cuts.

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Differential (2+1) jet event rates and determination of alpha(s) in deep inelastic scattering at HERA

The H1 collaboration Adloff, C. ; Anderson, M. ; Andreev, V. ; et al.
Eur.Phys.J. C5 (1998) 625-639, 1998.
Inspire Record 472304 DOI 10.17182/hepdata.44249

Events with a (2+1) jet topology in deep-inelastic scattering at HERA are studied in the kinematic range 200 < Q^2< 10,000 GeV^2. The rate of (2+1) jet events has been determined with the modified JADE jet algorithm as a function of the jet resolution parameter and is compared with the predictions of Monte Carlo models. In addition, the event rate is corrected for both hadronization and detector effects and is compared with next-to-leading order QCD calculations. A value of the strong coupling constant of alpha_s(M_Z^2)= 0.118+- 0.002 (stat.)^(+0.007)_(-0.008) (syst.)^(+0.007)_(-0.006) (theory) is extracted. The systematic error includes uncertainties in the calorimeter energy calibration, in the description of the data by current Monte Carlo models, and in the knowledge of the parton densities. The theoretical error is dominated by the renormalization scale ambiguity.

4 data tables

Y2 distribution corrected for detector effects.

Y2 distribution corrected for both detector and hadronization effects.

Y2 distribution using the E, E0 and P variants of the JADE alogrithm, corrected for both detector and hadronization effects. Statistical errors only.

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Dijet cross-sections in photoproduction at HERA

The ZEUS collaboration Breitweg, J. ; Derrick, M. ; Krakauer, D. ; et al.
Eur.Phys.J. C1 (1998) 109-122, 1998.
Inspire Record 450085 DOI 10.17182/hepdata.44384

Dijet cross sections are presented using photoproduction data obtained with the ZEUS detector during 1994. These measurements represent an extension of previous results, as the higher statistics allow cross sections to be measured at higher jet transverse energy (ETJ). Jets are identified in the hadronic final state using three different algorithms, and the cross sections compared to complete next-to-leading order QCD calculations. Agreement with these calculations is seen for the pseudorapidity dependence of the direct photon events with ETJ > 6 GeV and of the resolved photon events with ETJ > 11 GeV. Calculated cross sections for resolved photon processes with 6 GeV < ETJ < 11 GeV lie below the data.

28 data tables

Dijet cross section using the KTCLUS jet alogrithm with a minimum ET for each jet of 6 GeV and a requirement on X(NAME=GAMMA_OBS) to be 0.0 TO 1.0. The second DSYS errors are the correlated uncertainties.

Dijet cross section using the KTCLUS jet alogrithm with a minimum ET for each jet of 8 GeV and a requirement on X(NAME=GAMMA_OBS) to be 0.0 TO 1.0. The second DSYS errors are the correlated uncertainties.

Dijet cross section using the KTCLUS jet alogrithm with a minimum ET for each jet of 11 GeV and a requirement on X(NAME=GAMMA_OBS) to be 0.0 TO 1.0. The second DSYS errors are the correlated uncertainties.

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Measurement of the inclusive dijet cross-section in photoproduction and determination of an effective parton distribution in the photon

The H1 collaboration Adloff, C. ; Aid, S. ; Anderson, M. ; et al.
Eur.Phys.J. C1 (1998) 97-107, 1998.
Inspire Record 448035 DOI 10.17182/hepdata.44511

The double-differential inclusive di-jet cross section in photoproduction processes is measured with the H1 detector at HERA. The cross section is determined as a function of the average transverse jet energy E_T^jets for ranges of the fractional energy x_gamma^jets of the parton from the photon side. An effective leading order parton distribution in the photon is determined at large parton fractional energies for scales between 80<p_T^2<1250 GeV^2. The measurement is compatible with the logarithmic scale dependence that is predicted by perturbative QCD.

8 data tables

No description provided.

No description provided.

No description provided.

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Rapidity gaps between jets in photoproduction at HERA

The ZEUS collaboration Derrick, M. ; Krakauer, D. ; Magill, S. ; et al.
Phys.Lett. B369 (1996) 55-68, 1996.
Inspire Record 401492 DOI 10.17182/hepdata.44803

Photoproduction events which have two or more jets have been studied in the $W_{\gamma p}$ range 135GeV $< W_{\gamma p} <$ 280GeV with the ZEUS detector at HERA. A class of events is observed with little hadronic activity between the jets. The jets are separated by pseudorapidity intervals ($\Delta\eta$) of up to four units and have transverse energies greater than 6GeV. A gap is defined as the absence between the jets of particles with transverse energy greater than 300MeV. The fraction of events containing a gap is measured as a function of \deta. It decreases exponentially as expected for processes in which colour is exchanged between the jets, up to a value of $\Delta\eta \sim 3$, then reaches a constant value of about 0.1. The excess above the exponential fall-off can be interpreted as evidence for hard diffractive scattering via a strongly interacting colour singlet object.

2 data tables

No description provided.

No description provided.


Measurement of alpha-s from jet rates in deep inelastic scattering at HERA

The ZEUS collaboration Derrick, M. ; Krakauer, D. ; Magill, S. ; et al.
Phys.Lett. B363 (1995) 201-216, 1995.
Inspire Record 400436 DOI 10.17182/hepdata.44947

Jet production in deep inelastic scattering for $120<Q~2<3600$GeV$~2$ has been studied using data from an integrated luminosity of 3.2pb$~{-1}$ collected with the ZEUS detector at HERA. Jets are identified with the JADE algorithm. A cut on the angular distribution of parton emission in the $\gamma~*$-parton centre-of-mass system minimises the experimental and theoretical uncertainties in the determination of the jet rates. The jet rates, when compared to ${\cal O}$($\alpha_{s}$~2$) perturbative QCD calculations, allow a precise determination of $\alpha_{s}(Q)$ in three $Q~2$-intervals. The values are consistent with a running of $\alpha_{s}(Q)$, as expected from QCD. Extrapolating to $Q=M_{Z~0}$ yields $\alpha_{s}(M_{Z~0}) = 0.117\pm0.005(stat)~{+0.004}_{-0.005}(syst_{exp}) {\pm0.007}(syst_{theory})$.

3 data tables

2+1 jet rate as a function of ycut the jet algorithm cut-off value. Statistical errors only.

Measured values of Lambda-QCD in the MS Bar scheme and alpha_s as a function of Q**2. The second systematic uncertainty is related to the theoretical uncertainties .

Strong coupling constant alpha_s extrapolated to the Z0 mass.