211 research outputs found
DESY 05-110 ISSN 0418-9833 July 2005 Measurement of F
No full textMeasurements are presented of inclusive charm and beauty cross sections in e p collisions at HERA for values of photon virtuality 12 and of the Bjorken scaling variable 0.0002 0.005. The fractions of events containing charm and beauty quarks are determined using a method based on the impact parameter, in the transverse plane, of tracks to the primary vertex, as measured by the H1 vertex detector. Values for the structure functions F 2 are obtained. This is the first measurement of F 2 in this kinematic range. The results are found to be compatible with the predictions of perturbative quantum chromodynamics and with previous measurements of F 2 . To be submitted to Eur. Phys. J. C A. Aktas , V. Andreev , T. Anthonis , S. Aplin , A. Asmone , A. Astvatsatourov A. Babaev , S. Backovic , J. Bahr , A. Baghdasaryan , P. Baranov , E. Barrelet W. Bartel , S. Baudrand , S. Baumgartner , J. Becker , M. Beckingham , O. Behnke O. Behrendt , A. Belousov , Ch. Berger , N. Berger , J.C. Bizot , M.-O. Boenig V. Boudry , J. Bracinik , G. Brandt , V. Brisson , D.P. Brown , D. Bruncko F.W. Busser , A. Bunyatyan 12,38 , G. Buschhorn , L. Bystritskaya , A.J. Campbell S. Caron , F. Cassol-Brunner , K. Cerny , V. Cerny 16,47 , V. Chekelian , J.G. Contreras J.A. Coughlan , B.E. Cox , G. Cozzika , J. Cvach , J.B. Dainton , W.D. Dau K. Daum 37,43 , Y. de Boer , B. Delcourt , A. De Roeck 10,45 , K. Desch , E.A. De Wolf C. Diaconu , V. Dodonov , A. Dubak 31,46 , G. Eckerlin , V. Efremenko , S. Egli R. Eichler , F. Eisele , M. Ellerbrock , E. Elsen , W. Erdmann , S. Essenov A. Falkewicz , P.J.W. Faulkner , L. Favart , A. Fedotov , R. Felst ,..
DESY-01-104 ISSN 0418-9833 July 2001 On the Rise of the Proton Structure Function F 2
No full textA measurement of the derivative (@ ln F 2 =@ ln x) Q 2 (x; Q ) of the proton structure function F 2 is presented in the low x domain of deeply inelastic positron--proton scattering. For 5 10 x 0:01 and Q (x; Q ) is found to be independent of x and to increase linearly with ln Q . Submitted to Phys. Lett. B C. Adloff , V. Andreev , B. Andrieu , T. Anthonis , V. Arkadov , A. Astvatsatourov A. Babaev , J. Bahr , P. Baranov , E. Barrelet , W. Bartel , P. Bate , J. Becker A. Beglarian , O. Behnke , C. Beier , A. Belousov , T. Benisch , Ch. Berger T. Berndt , J.C. Bizot , J. Boehme, V. Boudry , W. Braunschweig , V. Brisson H.-B. Broker , D.P. Brown , W. Bruckner , D. Bruncko , J. Burger , F.W. Busser A. Bunyatyan 12;34 , A. Burrage , G. Buschhorn , L. Bystritskaya , A.J. Campbell J. Cao , S. Caron , F. Cassol-Brunner , D. Clarke , B. Clerbaux , C. Collard J.G. Contreras 7;41 , Y.R. Coppens , J.A. Coughlan , M.-C. Cousinou , B.E. Cox G. Cozzika , J. Cvach , J.B. Dainton , W.D. Dau , K. Daum 33;39 , M. Davidsson B. Delcourt , N. Delerue , R. Demirchyan , A. De Roeck 10;43 , E.A. De Wolf C. Diaconu , J. Dingfelder , P. Dixon , V. Dodonov , J.D. Dowell , A. Droutskoi A. Dubak , C. Duprel , G. Eckerlin , D. Eckstein , V. Efremenko , S. Egli R. Eichler , F. Eisele , E. Eisenhandler , M. Ellerbrock , E. Elsen , M. Erdmann 10;40;e W. Erdmann , P.J.W. Faulkner , L. Favart , A. Fedotov , R. Felst , J. Ferencei S. Ferron , M. Fleischer , Y.H. Fleming , G. Flugge , A. Fomenko , I. Foresti J. Formanek , G. Franke , E. Gabathuler , K. Gabathuler , J. Garvey , J. Gassner J. Gayler ..
DESY 04--083 ISSN 0918--9833 Measurement of the Proton Structure Function F 2
No full textThe proton structure function F 2 (x, Q ) is measured in inelastic QED Compton scattering using data collected with the H1 detector at HERA.QED Compton events are used to access the kinematic range of very low virtualities of the exchanged photon, Q , down to 0.5 GeV and Bjorken x up to #0.06, a region which has not been covered previously by inclusive measurements at HERA. The results are in agreement with the measurements from fixed target lepton-nucleon scattering experiments. Submitted to Physics Letters B A. Aktas , V. Andreev , T. Anthonis , A. Asmone , A. Babaev , S. Backovic , J. Bahr P. Baranov , E. Barrelet , W. Bartel , S. Baumgartner , J. Becker , M. Beckingham O. Behnke , O. Behrendt , A. Belousov , Ch. Berger , N. Berger , T. Berndt , J.C. Bizot J. Bohme , M.-O. Boenig , V. Boudry , J. Bracinik , V. Brisson , H.-B. Broker D.P. Brown , D. Bruncko , F.W. Busser , A. Bunyatyan 12,36 , G. Buschhorn L. Bystritskaya , A.J. Campbell , S. Caron , F. Cassol-Brunner , K. Cerny , V. Chekelian C. Collard , J.G. Contreras , Y.R. Coppens , J.A. Coughlan , B.E. Cox , G. Cozzika J. Cvach , J.B. Dainton , W.D. Dau , K. Daum 35,41 , B. Delcourt , R. Demirchyan A. De Roeck 10,44 , K. Desch , E.A. De Wolf , C. Diaconu , J. Dingfelder , V. Dodonov A. Dubak , C. Duprel , G. Eckerlin , V. Efremenko , S. Egli , R. Eichler , F. Eisele M. Ellerbrock , E. Elsen , M. Erdmann 10,42 , W. Erdmann , P.J.W. Faulkner , L. Favart A. Fedotov , R. Felst , J. Ferencei , M. Fleischer , P. Fleischmann , Y.H. Fleming G. Flucke , G. Flugge , A. Fomenko , I. Foresti , J. Formanek , G. Franke , G. Frising E. Gabathuler , K. Gabath..
Imaging performance of the hybrid pixel detectors XPAD3-S
No full textHybrid pixel detectors, originally developed for tracking particles in high-energy physics experiments, have recently been used in material sciences and macromolecular crystallography. Their capability to count single photons and to apply a threshold on the photon energy suggests that they could be optimal digital x-ray detectors in low energy beams such as for small animal computed tomography (CT). To investigate this issue, we have studied the imaging performance of photon counting hybrid pixel detectors based on the XPAD3-S chip. Two detectors are considered, connected either to a Si or to a CdTe sensor, the latter being of interest for its higher efficiency. Both a standard 'International Electrotechnical Commission' (IEC) mammography beam and a beam used for mouse CT results published in the literature are employed. The detector stability, linearity and noise are investigated as a function of the dose for several imaging exposures (~0.1–400 µGy). The perfect linearity of both detectors is confirmed, but an increase in internal noise for counting statistics higher than ~5000 photons has been found, corresponding to exposures above ~110 µGy and ~50 µGy for the Si and CdTe sensors, respectively. The noise power spectrum (NPS), the modulation transfer function (MTF) and the detective quantum efficiency (DQE) are then measured for two energy threshold configurations (5 keV and 18 keV) and three doses (~3, 30 and 300 µGy), in order to obtain a complete estimation of the detector performances. In general, the CdTe sensor shows a clear superiority with a maximal DQE(0) of ~1, thanks to its high efficiency (~100%). The DQE of the Si sensor is more dependent on the radiation quality, due to the energy dependence of its efficiency its maximum is ~0.4 with respect to the softer radiation. Finally, we compare the XPAD3-S DQE with published curves of other digital devices in a similar radiation condition. The XPAD3-S/CdTe detector appears to be the best with the highest DQE at low frequency, although some improvements are expected to reduce the increase of noise with the counts statistics and to guarantee a better stability of the detector response. General scientific summary. Hybrid pixel detectors count single photons by applying a threshold on the photon energy. Hence, they can provide optimal digital x-ray detectors for low energy beams as used in small animal CT. To investigate this issue, we have studied the imaging performance of photon counting hybrid pixel detectors based on the XPAD3-S chip. Two detectors were considered, either connected to a Si or to a CdTe sensor. Figures of merit (linearity, MTF, NPS and DQE) were measured for both types of sensor by using standard beams. Results are given as a function of the dose, for typical small animal imaging exposures. The perfect linearity of both detectors is confirmed, but an increase in internal noise for counting statistics higher than ~5000 photons has been observed. In general, the CdTe sensor demonstrated a clear superiority with a DQE(0) close to 1. The DQE of the Si sensor is more dependent on the radiation quality, due to the energy dependence of its efficiency its maximum DQE(0) is about 0.4
Measured Imaging Performance of Photon Couting Hybrid-Pixel X-Ray Detectors
No full textInternational audienceThe imaging performance of photon counting hybrid pixel X-ray detectors based on the XPAD chip is presented. The noise power spectrum, the modulation transfer function and the detective quantum efficiency of the imaging systems are evaluated in the case of a standard mammography beam and a common micro-CT beam. The study is based on two XPAD3-S chips, connected either to a Si or to a CdTe sensor, the latter being of interest for its higher efficiency. Both detectors consist of 9600 pixels (130 μm × 130 μm) organized in a 80 × 120 matrix and allow for the setting of an energy threshold on the detected photons. Results are given as function of the dose, for typical small animal imaging exposures. The stability and linearity of the detectors and the influence of the energy threshold on the image quality are investigated. Finally, the performance of hybrid pixels is compared with commercially available devices used in mouse computed tomography imaging
A Determination of Electroweak Parameters at HERA H1 Collaboration
No full textUsing the deep inelastic e p and e - p charged and neutral current scattering cross sections previously published, a combined electroweak and QCD analysis is performed to determine electroweak parameters accounting for their correlation with parton distributions. The data used have been collected by the H1 experiment in 1994-2000 and correspond to an integrated luminosity of 117.2 pb -1 . A measurement is obtained of the W propagator mass in charged current ep scattering. The weak mixing angle sin # W is determined in the onmass -shell renormalisation scheme. A first measurement at HERA is made of the light quark weak couplings to the Z boson and a possible contribution of right-handed isospin components to the weak couplings is investigated. (To be submitted to Phys. Lett. B.) A. Aktas , V. Andreev , T. Anthonis , S. Aplin , A. Asmone , A. Astvatsatourov A. Babaev , S. Backovic , J. Bahr , A. Baghdasaryan , P. Baranov , E. Barrelet W. Bartel , S. Baudrand , S. Baumgartner , J. Becker , M. Beckingham , O. Behnke O. Behrendt , A. Belousov , Ch. Berger , N. Berger , J.C. Bizot , M.-O. Boenig V. Boudry , J. Bracinik , G. Brandt , V. Brisson , D.P. Brown , D. Bruncko F.W. Busser , A. Bunyatyan 12,38 , G. Buschhorn , L. Bystritskaya , A.J. Campbell S. Caron , F. Cassol-Brunner , K. Cerny , V. Cerny 16,47 , V. Chekelian , J.G. Contreras J.A. Coughlan , B.E. Cox , G. Cozzika , J. Cvach , J.B. Dainton , W.D. Dau K. Daum 37,43 , Y. de Boer , B. Delcourt , A. De Roeck 10,45 , K. Desch , E.A. De Wolf C. Diaconu , V. Dodonov , A. Dubak 31,46 , G. Eckerlin , V. Efremenko , S. Egli R. Eichler , F. Eisele , M. Ellerbrock , W. Erdmann , S. Essenov , A. F..
Neutron imaging with the XPAD3-s hybrid pixel detector
No full textThe X-ray photon counting hybrid pixel camera XPAD3-S is a promising detector for small animal X-ray radiography and tomography. The increasing interest in neutron imaging as a complementary approach to X-ray imaging motivates the study of the potentialities of this device for neutrons. To investigate this issue, we have studied the response of XPAD3-S to alpha particles and cold neutrons. The neutron detection was obtained with passive converters placed in front of the sensor. This choice permits to easily assemble 2D neutron sensitive imagers without size constraints; it penalizes however the detector efficiency with respect to other solutions. In this paper, we first analyze the detector response to alpha particles under several conditions, then we investigate its imaging performances and its detection efficiency for cold neutrons. Finally, we present the first XPAD3-S neutron tomography. Most of the results are validated by Monte Carlo simulations that will also permit to extrapolate the detector response to thermal neutrons
DESY 06-044 ISSN 0418-9833 April 2006 Search for a Narrow Baryonic Resonance Decaying to K
No full textA search for a narrow baryonic resonance decaying to K s p is carried out in deep inelastic ep scattering with the H1 detector at HERA. Such a resonance could be a strange pentaquark Q , evidence for which has been reported by several experiments. The K s p invariant mass distributions presented here do not show any significant peak in the mass range from threshold up to 1.7 GeV. Mass dependent upper limits on s(ep p) are obtained at the 95% confidence level. Submitted to Phys. Lett. B A. Aktas , V. Andreev , T. Anthonis , B. Antunovic , S. Aplin , A. Asmone A. Astvatsatourov , A. Babaev 24,+ , S. Backovic , A. Baghdasaryan , P. Baranov E. Barrelet , W. Bartel , S. Baudrand , S. Baumgartner , J. Becker , M. Beckingham O. Behnke , O. Behrendt , A. Belousov , N. Berger , J.C. Bizot , M.-O. Boenig V. Boudry , J. Bracinik , G. Brandt , V. Brisson , D. Bruncko , F.W. Busser A. Bunyatyan 11,37 , G. Buschhorn , L. Bystritskaya , A.J. Campbell , F. Cassol-Brunner K. Cerny , V. Cerny 15,46 , V. Chekelian , J.G. Contreras , J.A. Coughlan , B.E. Cox G. Cozzika , J. Cvach , J.B. Dainton , W.D. Dau , K. Daum 36,42 , Y. de Boer B. Delcourt , M. Del Degan , A. De Roeck 9,44 , E.A. De Wolf , C. Diaconu , V. Dodonov A. Dubak 30,45 , G. Eckerlin , V. Efremenko , S. Egli , R. Eichler , F. Eisele , A. Eliseev E. Elsen , S. Essenov , A. Falkewicz , P.J.W. Faulkner , L. Favart , A. Fedotov , R. Felst J. Feltesse , J. Ferencei , L. Finke , M. Fleischer , G. Flucke , A. Fomenko , G. Franke T. Frisson , E. Gabathuler , E. Garutti , J. Gayler , C. Gerlich , S. Ghazaryan S. Ginzburgskaya , A. Glazov , I. Glushkov ..
Evidence for a Narrow Anti-Charmed Baryon State H1 Collaboration
No full textA narrow resonance in D # - p and D # p invariant mass combinations is observed in inelastic electron-proton collisions at centre-of-mass energies of 300 GeV and 320 GeV at HERA. The resonance has a mass of 3099 5 (syst.) MeV and a measured Gaussian width of 12 3 (stat.) MeV, compatible with the experimental resolution. The resonance is interpreted as an anti-charmed baryon with a minimal constituent quark composition of uuddc, together with the charge conjugate. To be submitted to Phys. Lett. B A. Aktas , V. Andreev , T. Anthonis , A. Asmone , A. Babaev , S. Backovic , J. Bahr P. Baranov , E. Barrelet , W. Bartel , S. Baumgartner , J. Becker , M. Beckingham O. Behnke , O. Behrendt , A. Belousov , Ch. Berger , N. Berger , T. Berndt , J.C. Bizot J. Bohme , M.-O. Boenig , V. Boudry , J. Bracinik , V. Brisson , H.-B. Broker D.P. Brown , D. Bruncko , F.W. Busser , A. Bunyatyan 12,36 , G. Buschhorn L. Bystritskaya , A.J. Campbell , S. Caron , F. Cassol-Brunner , K. Cerny V. Chekelian , C. Collard , J.G. Contreras , Y.R. Coppens , J.A. Coughlan , B.E. Cox G. Cozzika , J. Cvach , J.B. Dainton , W.D. Dau , K. Daum 35,41 , B. Delcourt R. Demirchyan , A. De Roeck 10,44 , K. Desch , E.A. De Wolf , C. Diaconu J. Dingfelder , V. Dodonov , A. Dubak , C. Duprel , G. Eckerlin , V. Efremenko S. Egli , R. Eichler , F. Eisele , M. Ellerbrock , E. Elsen , M. Erdmann 10,42 W. Erdmann , P.J.W. Faulkner , L. Favart , A. Fedotov , R. Felst , J. Ferencei M. Fleischer , P. Fleischmann , Y.H. Fleming , G. Flucke , G. Flugge , A. Fomenko I. Foresti , J. Formanek , G. Franke , G. Frising , E. Gabathuler , K. Gabathuler E. G..
- …
