Multi-Jet Event Rates in Deep Inelastic Scattering and Determination of the Strong Coupling Constant

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).Comment: 17 pages, 4 figures, 3 tables, this version to appear in Eur. Phys. J.; it replaces first posted hep-ex/9807019 which had incorrect figure 4

Differential (2+1) Jet Event Rates and Determination of alpha_s in Deep Inelastic Scattering at HERA

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.Comment: 25 pages, 6 figures, 3 tables, submitted to Eur. Phys.

Multiplicity Structure of the Hadronic Final State in Diffractive Deep-Inelastic Scattering at HERA

The multiplicity structure of the hadronic system X produced in deep-inelastic processes at HERA of the type ep -> eXY, where Y is a hadronic system with mass M_Y< 1.6 GeV and where the squared momentum transfer at the pY vertex, t, is limited to |t|<1 GeV^2, is studied as a function of the invariant mass M_X of the system X. Results are presented on multiplicity distributions and multiplicity moments, rapidity spectra and forward-backward correlations in the centre-of-mass system of X. The data are compared to results in e+e- annihilation, fixed-target lepton-nucleon collisions, hadro-produced diffractive final states and to non-diffractive hadron-hadron collisions. The comparison suggests a production mechanism of virtual photon dissociation which involves a mixture of partonic states and a significant gluon content. The data are well described by a model, based on a QCD-Regge analysis of the diffractive structure function, which assumes a large hard gluonic component of the colourless exchange at low Q^2. A model with soft colour interactions is also successful.Comment: 22 pages, 4 figures, submitted to Eur. Phys. J., error in first submission - omitted bibliograph

Measurements of Transverse Energy Flow in Deep-Inelastic Scattering at HERA

Measurements of transverse energy flow are presented for neutral current deep-inelastic scattering events produced in positron-proton collisions at HERA. The kinematic range covers squared momentum transfers Q^2 from 3.2 to 2,200 GeV^2, the Bjorken scaling variable x from 8.10^{-5} to 0.11 and the hadronic mass W from 66 to 233 GeV. The transverse energy flow is measured in the hadronic centre of mass frame and is studied as a function of Q^2, x, W and pseudorapidity. A comparison is made with QCD based models. The behaviour of the mean transverse energy in the central pseudorapidity region and an interval corresponding to the photon fragmentation region are analysed as a function of Q^2 and W.Comment: 26 pages, 8 figures, submitted to Eur. Phys.

Energy Flow in the Hadronic Final State of Diffractive and Non-Diffractive Deep-Inelastic Scattering at HERA

An investigation of the hadronic final state in diffractive and non--diffractive deep--inelastic electron--proton scattering at HERA is presented, where diffractive data are selected experimentally by demanding a large gap in pseudo --rapidity around the proton remnant direction. The transverse energy flow in the hadronic final state is evaluated using a set of estimators which quantify topological properties. Using available Monte Carlo QCD calculations, it is demonstrated that the final state in diffractive DIS exhibits the features expected if the interaction is interpreted as the scattering of an electron off a current quark with associated effects of perturbative QCD. A model in which deep--inelastic diffraction is taken to be the exchange of a pomeron with partonic structure is found to reproduce the measurements well. Models for deep--inelastic $ep$ scattering, in which a sizeable diffractive contribution is present because of non--perturbative effects in the production of the hadronic final state, reproduce the general tendencies of the data but in all give a worse description.Comment: 22 pages, latex, 6 Figures appended as uuencoded fil

Phase II study of docetaxel and irinotecan combination chemotherapy in metastatic gastric carcinoma

The current treatment for metastatic gastric cancer (MGC) consists of cisplatin and/or fluorouracil (5-FU) based combination chemotherapy, but cisplatin-based regimens are associated with considerable toxicity. We evaluated the efficacy and safety of a noncisplatin-, non-5-FU-containing regimen, docetaxel/irinotecan in MGC. Chemo-naive patients with MGC received docetaxel (30 mg m−2) and irinotecan (70 mg m−2) on days 1 and 8 every 3 weeks. The 48 eligible patients (median age 56 years) received a median of four cycles of docetaxel/irinotecan (range 1–18). Of the 46 patients in whom efficacy could be evaluated, 21 showed a partial response (response rate=45.7%; 95% confidence interval (CI) 31.3–60.1%). At a median follow-up of 15.0 months, the median time to progression was 4.5 months (95% CI 3.8–5.2 months) and overall survival was 8.2 months (95% CI, 5.8–10.6 months). Grade 3/4 neutropenia developed in 57.4% of patients, and febrile neutropenia/neutropenic infection in 19.1%. Nonhaematological toxicities were moderate; grade 3/4 diarrhoea occurred in 19.1% of patients, however, was manageable by a dose reduction. There was one possible treatment-related death. In conclusion, weekly docetaxel/irinotecan is a promising outpatient regimen in MGC, with appropriate dose modification

Measurement of Leading Proton and Neutron Production in Deep Inelastic Scattering at HERA

Deep--inelastic scattering events with a leading baryon have been detected by the H1 experiment at HERA using a forward proton spectrometer and a forward neutron calorimeter. Semi--inclusive cross sections have been measured in the kinematic region 2 <= Q^2 <= 50 GeV^2, 6.10^-5 <= x <= 6.10^-3 and baryon p_T <= MeV, for events with a final state proton with energy 580 <= E' <= 740 GeV, or a neutron with energy E' >= 160 GeV. The measurements are used to test production models and factorization hypotheses. A Regge model of leading baryon production which consists of pion, pomeron and secondary reggeon exchanges gives an acceptable description of both semi-inclusive cross sections in the region 0.7 <= E'/E_p <= 0.9, where E_p is the proton beam energy. The leading neutron data are used to estimate for the first time the structure function of the pion at small Bjorken--x.Comment: 30 pages, 9 figures, 2 tables, submitted to Eur. Phys.

A phase II study of biweekly dose-intensified oral capecitabine plus irinotecan (bXELIRI) for patients with advanced or metastatic gastric cancer

Capecitabine, a prodrug of 5-FU, has been reported to generate maximal tumour activity at tumour sites and/or to improve drug tolerability as compared with 5-FU infusion, and it has also been demonstrated to act synergistically with irinotecan against some solid cancers. A previous study concluded that dose-intensified biweekly capecitabine seems to be more effective at increasing both response rate and progression-free survival time than conventional dose and schedule of capecitabine in colon cancer. We conducted this study to ascertain the efficacy and toxicity of dose-intensified biweekly capecitabine and irinotecan combination chemotherapy in chemotherapy-naïve advanced or metastatic gastric cancer patients. Patients were treated with irinotecan 130 mg m−2 intravenously for 90 min on days 1 and 15. Capecitabine at 3500 mg m−2 day−1, divided into two sessions per day, was administered for seven consecutive days from days 1 and 15, and followed by a 7-day drug-free period, respectively. Fifty-five eligible patients were enrolled in this study from November 2003 to April 2006. There were 22 women and 33 men: median patient age was 54 years (range: 27–81). A total of 200 treatment cycles were administered at a median number of four per patient (range: 1–9). Intent-to-treatment analysis showed that one patient achieved complete response (1.8%), 23 partial response (41.8%), 15 stable disease (27.3%), 10 progressive disease (18.2%) and 6 were non-evaluable (10.9%). The overall response rate was 43.6% (95% confidence interval: 30.2–56.9). The common grade 3–4 toxicities were neutropenia in 12 (21.8%), nausea/vomiting in 3 (5.4%) and diarrhea in 4 (7.2%) patients. Median time to progression was 5 months (range: 0.5–11 months), median survival duration was 11 months (range: 0.5–45 months) and median response duration was 6 months (range: 0.5–9 months). Biweekly dose-intensified capecitabine and irinotecan combination chemotherapy was active for the treatment of advanced or metastatic gastric cancers with a tolerable safety profile

FOLFOXIRI (folinic acid, 5-fluorouracil, oxaliplatin and irinotecan) vs FOLFIRI (folinic acid, 5-fluorouracil and irinotecan) as first-line treatment in metastatic colorectal cancer (MCC): a multicentre randomised phase III trial from the Hellenic Oncology Research Group (HORG)

To compare the efficacy and toxicity of oxaliplatin (L-OHP) in combination with irinotecan (CPT-11), 5-fluorouracil (5-FU) and leucovorin (LV) (FOLFOXIRI) vs irinotecan and 5-FU/LV (FOLFIRI) as first-line treatment of patients with metastatic colorectal cancer (MCC). A total of 283 chemotherapy-naïve patients with MCC were enrolled (FOLFIRI arm: n=146; FOLFOXIRI arm: n=137). In the FOLFOXIRI arm, CPT-11 (150 mg m−2) was given on d1, L-OHP (65 mg m−2) on d2, LV (200 mg m−2) on days 2 and 3 and 5-FU (400 mg m−2 as i.v. bolus and 600 mg m−2 as 22 h i.v. continuous infusion) on days 2 and 3. In the FOLFIRI arm, CPT-11 (180 mg m−2) was given on d1 whereas LV and 5-FU were administered in the same way as in the FOLFOXIRI regimen. Both regimens were administered every 2 weeks. There was no difference in terms of overall survival (median OS: 19.5 and 21.5 months, for FOLFIRI and FOLFOXIRI, respectively; P=0.337), median time to disease progression (FOLFIRI: 6.9 and FOLFOXIRI: 8.4 months; P=0.17), response rates (33.6 and 43% for FOLFIRI and FOLFOXIRI, respectively; P=0.168). Patients treated with FOLFOXIRI had a significantly higher incidence of alopecia (P=0.0001), diarrhoea (P=0.0001) and neurosensory toxicity (P=0.001) compared with patients treated with FOLFIRI. The present study failed to demonstrate any superiority of the FOLFOXIRI combination compared with the FOLFIRI regimen, although the observed median OS is one of the best ever reported in the literature