Measuring Transversity in Polarized P+p Collisions with Di-hadron Correlations at √s PDF Download
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Author: Keith Landry
Publisher:
ISBN:
Category :
Languages : en
Pages : 168
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The transversity distribution, $h_1(x)$, of a transversely polarized proton describes the probability of partons with polarization parallel to the parent proton, carrying a momentum fraction $x$ of the parent proton. This distribution is fundamental for our understanding of the proton spin structure but still very much unknown for values of $x$ larger than about 0.15. We study transversely spin-polarized proton collisions at $\sqrt{s}=200$ GeV from STAR, because polarized p+p collisions at RHIC can access this $x$ region and, with a higher scale and transverse momentum, probe a different kinematic regime than SIDIS. We find sizable spin asymmetries in di-hadron correlations, which can be used to directly probe the transversity distribution of quarks inside protons because they arise from a transversely spin polarized quark fragmenting into two hadrons by the Interference Fragmentation Function.
Author: Keith Landry
Publisher:
ISBN:
Category :
Languages : en
Pages : 168
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Book Description
The transversity distribution, $h_1(x)$, of a transversely polarized proton describes the probability of partons with polarization parallel to the parent proton, carrying a momentum fraction $x$ of the parent proton. This distribution is fundamental for our understanding of the proton spin structure but still very much unknown for values of $x$ larger than about 0.15. We study transversely spin-polarized proton collisions at $\sqrt{s}=200$ GeV from STAR, because polarized p+p collisions at RHIC can access this $x$ region and, with a higher scale and transverse momentum, probe a different kinematic regime than SIDIS. We find sizable spin asymmetries in di-hadron correlations, which can be used to directly probe the transversity distribution of quarks inside protons because they arise from a transversely spin polarized quark fragmenting into two hadrons by the Interference Fragmentation Function.
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Category :
Languages : en
Pages :
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We report the first measurement of the opening angledistribution between pairs of jets produced in high-energy collisions oftransversely polarized protons. The measurement probes (Sivers)correlations between the transverse spin orientation of a proton and thetransverse momentum directions of its partons. With both beams polarized, the wide pseudorapidity ( -1 leq eta leq +2) coverage for jets permitsseparation of Sivers functions for the valence and sea regions. Theresulting asymmetries are all consistent with zero and considerablysmaller than Sivers effects observed in semi-inclusive deep inelasticscattering (SIDIS). We discuss theoretical attempts to reconcile the newresults with the sizable transverse spin effects seen in SIDIS andforward hadron production in pp collisions.
Author: James Lucas Drachenberg
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Category :
Languages : en
Pages :
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One unresolved question in hadronic physics is the origin of large transverse single-spin asymmetries, AN, observed in hadron production from high-energy polarized-proton collisions. Collinear perturbative Quantum Chromodynamics (pQCD) predicts that AN should scale with the quark mass, however, experiments have since reported large AN for inclusive hadron production. Recent measurements from RHIC experiments show examples of these asymmetries at forward angles in a kinematic region where pQCD cross-section calculations reasonably agree with measured cross-sections. Disentangling dynamical contributions to AN from hadro-production requires moving beyond inclusive measurements. One possibility is to investigate asymmetries in two-particle correlations due to Interference Fragmentation Functions (IFF) and the Sivers effect. In 2008, RHIC dedicated a portion of the run to transversely polarized proton collisions at sqrt(s) = 200 GeV. STAR was equipped with a Foward Meson Spectrometer (FMS) and a Forward Time Projection Chamber (FTPC), overlapping in the pseudorapidity range of 2.5 eta & lt; 4. By analyzing neutral pions with the FMS correlated with charged particles from the FTPC, correlation asymmetries can be measured at kinematics where large inclusive asymmetries have been measured. Correlations are measured for pi^0's with 2 & lt; pT, pi^0 & lt; 5 GeV/c and associated charged particles in two ranges of transverse momentum: 1 & lt; pT, ch & lt; 2 GeV/c and 0.5 & lt; pT, ch & lt; 1 GeV/c. IFF and Sivers asymmetries manifest themselves through the correlation of two particles from the same jet. These events are selected through a cut on the pair radius, delta R. Gain non-uniformities and electronics failures have resulted in large holes in trigger acceptance and associated particle acceptance, respectively. This non-uniform acceptance allows the Sivers and IFF effects to mix and distort the raw asymmetries. Techniques are developed to measure this leak-through by means of unpolarized yields and event weighting. They result in small corrections to the asymmetries. IFF and Sivers asymmetries both for xF 0 and for xF & lt; 0 are reported for forward-angle pi^0-charged particle correlations from polarized-proton collisions at sqrt(s) = 200 GeV. Asymmetries are shown corrected for full underlying-event and pileup backgrounds, as well as corrected only for pile-up contributions. It appears the asymmetries are less sensitive to delta R when corrected for the full underlying-event background. Unfortunately, statistics limitations preclude a firm conclusion.
Author: Boris Lemmer
Publisher: Springer
ISBN: 3319189328
Category : Science
Languages : en
Pages : 246
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This thesis introduces readers to the Standard Model, the top quark and its properties, before explaining the concept of spin correlation measurement. The first measurement of top quark spin correlations at the LHC in the lepton+jets decay channel is presented. As the heaviest elementary particle, the top quark plays an essential role in the Standard Model of elementary particle physics. In the case of top quarks being produced in pairs at hadron colliders, the Standard Model predicts their spins to be correlated. The degree of correlation depends on both the production mechanism and properties of the top quark. Any deviation from the Standard Model prediction can be an indicator for new physics phenomena. The thesis employs an advanced top quark reconstruction algorithm including dedicated identification of the up- and down-type quarks from the W boson decay.
Author: Alexei Prokudin
Publisher: World Scientific
ISBN: 9811214964
Category : Science
Languages : en
Pages : 344
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This book contains proceedings of the 7-week INT program dedicated to the physics of the Electron-Ion Collider (EIC), the world's first polarized electron-nucleon (ep) and electron-nucleus (eA) collider to be constructed in the United States. The 2015 NSAC Long Range Plan recommended EIC as the 'highest priority for new facility construction following the completion of FRIB'. The primary goal of the EIC is to establish precise multi-dimensional imaging of quarks and gluons inside nucleons and nuclei. This includes (i) understanding the spatial and momentum space structure of the nucleon through the studies of TMDs (transverse-momentum-dependent parton distributions), GPD (generalized parton distributions) and the Wigner distribution; (ii) determining the partonic origin of the nucleon spin; (iii) exploring the new quantum chromodynamics (QCD) frontier of ultra-strong gluon fields, with the potential to seal the discovery of a new form of dense gluon matter predicted to exist in all nuclei and nucleons at small Bjorken x — the parton saturation.The program brought together both theorists and experimentalists from Jefferson Lab (JLab), Brookhaven National Laboratory (BNL) along with the national and international nuclear physics communities to assess and advance the EIC physics.
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Category :
Languages : en
Pages :
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The total and differential cross sections for inclusive production of $\mathrm{B}^{+}$ hadrons are measured as a function of the $\mathrm{B}^{+}$ transverse momentum $p_{\mathrm{T}}^\mathrm{B}$ and rapidity $y^\mathrm{B}$ in pp collisions at a centre-of-mass energy of 13 TeV, using data collected by the CMS experiment that correspond to an integrated luminosity of 49.4 pb$^{-1}$. The measurement uses the exclusive decay channel $\mathrm{B}^{+} \to \mathrm{J}/\psi \mathrm{K}^{+}$, with $\mathrm{J}/\psi$ mesons that decay to a pair of muons. The results show a reasonable agreement with theoretical calculations within the uncertainties.
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ISBN: 9789178956043
Category :
Languages : en
Pages :
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Author:
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Category :
Languages : en
Pages :
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We report a new measurement of the midrapidity inclusive jet longitudinal double-spin asymmetry, ALL, in polarized pp collisions at center-of-mass energy √s = 200 GeV. The STAR data place stringent constraints on polarized parton distribution functions extracted at next-to-leading order from global analyses of inclusive deep-inelastic scattering (DIS), semi-inclusive DIS, and RHIC pp data. Lastly, the measured asymmetries provide evidence at the 3? level for positive gluon polarization in the Bjorken-x region x > 0.05 .
Author: Guiseppe Ciullo
Publisher: World Scientific
ISBN: 9814467448
Category : Science
Languages : en
Pages : 313
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Transversity 2008, the second workshop on “Transverse polarization phenomena in hard processes” follows the first one held in Como after three years. As in that case, the event comes at the end of a two-years project financed by the Italian Ministry of Education.In the time between the two Workshops, decisive steps towards the revealing of the transverse spin structure of the proton were taken on both the theoretical and experimental sides.The milestone of the first extraction of Transversity and the Sivers function for the u- and d-quarks deserves a special mention. In the same period, historic experiments that in the last decade contributed to the first pioneering measurements in the SIDIS sector, have concluded their data taking, and their place is being taken by upgrades of existing or new facilities. These are the result of the new interesting phenomena which are appearing and call for additional experimental information and novel experimental techniques.Over 80 physicists took part in the Workshop. Equally involved were experimentalists and theoreticians engaged in investigating the nature of transverse spin. The heterogeneous public favoured vivid discussions and fruitful exchange of up-to-date theoretical and experimental ideas on this constantly evolving subject.
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Category : Power resources
Languages : en
Pages : 578
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