A high-statistics measurement of transverse spin effects in dihadron production from muon-proton semi-inclusive deep-inelastic scattering
C. Adolph, R. Akhunzyanov, M. G. Alekseev, Yu. Alexandrov, G. D. Alexeev, A. Amoroso, V. Andrieux, V. Anosov, A. Austregesilo, B. Badelek, F. Balestra, J. Barth… 展开作者
C. Adolph, R. Akhunzyanov, M. G. Alekseev, Yu. Alexandrov, G. D. Alexeev, A. Amoroso, V. Andrieux, V. Anosov, A. Austregesilo, B. Badelek, F. Balestra, J. Barth, G. Baum, R. Beck, Y. Bedfer, A. Berlin, J. Bernhard, R. Bertini, K. Bicker, J. Bieling, R. Birsa, J. Bisplinghoff, M. Bodlak, M. Boer, P. Bordalo, F. Bradamante, C. Braun, A. Bravar, A. Bressan, M. Buechele, E. Burtin, L. Capozza, M. Chiosso, S. U. Chung, A. Cicuttin, M. L. Crespo, Q. Curiel, S. Dalla Torre, S. S. Dasgupta, S. Dasgupta, O. Yu. Denisov, S. V. Donskov, N. Doshita, V. Duic, W. Duennweber, M. Dziewiecki, A. Efremov, C. Elia, P. D. Eversheim, W. Eyrich, M. Faessler, A. Ferrero, A. Filin, M. Finger, M. Finger, H. Fischer, C. Franco, N. du Fresne von Hohenesche, J. M. Friedrich, V. Frolov, R. Garfagnini, F. Gautheron, O. P. Gavrichtchouk, S. Gerassimov, R. Geyer, M. Giorgi, I. Gnesi, B. Gobbo, S. Goertz, M. Gorzellik, S. Grabmueller, A. Grasso, B. Grube, A. Guskov, T. Guthoerl, F. Haas, D. von Harrach, D. Hahne, R. Hashimoto, F. H. Heinsius, F. Herrmann, F. Hinterberger, Ch. Hoeppner, N. Horikawa, N. d'Hose, S. Huber, S. Ishimoto, A. Ivanov, Yu. Ivanshin, T. Iwata, R. Jahn, V. Jary, P. Jasinski, P. Joerg, R. Joosten, E. Kabuss, D. Kang, B. Ketzer, G. V. Khaustov, Yu. A. Khokhlov, Yu. Kisselev, F. Klein, K. Klimaszewski, J. H. Koivuniemi, V. N. Kolosov, K. Kondo, K. Koenigsmann, I. Konorov, V. F. Konstantinov, A. M. Kotzinian, O. Kouznetsov, Z. Kral, M. Kraemer, Z. V. Kroumchtein, N. Kuchinski, F. Kunne, K. Kurek, R. P. Kurjata, A. A. Lednev, A. Lehmann, S. Levorato, J. Lichtenstadt, A. Maggiora, A. Magnon, N. Makke, G. K. Mallot, C. Marchand, A. Martin, J. Marzec, J. Matousek, H. Matsuda, T. Matsuda, G. Meshcheryakov, W. Meyer, T. Michigami, Yu. V. Mikhailov, Y. Miyachi, A. Nagaytsev, T. Nagel, F. Nerling, S. Neubert, D. Neyret, V. I. Nikolaenko, J. Novy, W. -D. Nowak, A. S. Nunes, I. Orlov, A. G. Olshevsky, M. Ostrick, R. Panknin, D. Panzieri, B. Parsamyan, S. Paul, M. Pesek, D. Peshekhonov, G. Piragino, S. Platchkov, J. Pochodzalla, J. Polak, V. A. Polyakov, J. Pretz, M. Quaresma, C. Quintans, S. Ramos, G. Reicherz, E. Rocco, V. Rodionov, E. Rondio, A. Rychter, N. S. Rossiyskaya, D. I. Ryabchikov, V. D. Samoylenko, A. Sandacz, S. Sarkar, I. A. Savin, G. Sbrizzai, P. Schiavon, C. Schill, T. Schlueter, A. Schmidt, K. Schmidt, H. Schmieden, K. Schoenning, S. Schopferer, M. Schott, O. Yu. Shevchenko, L. Silva, L. Sinha, S. Sirtl, M. Slunecka, S. Sosio, F. Sozzi, A. Srnka, L. Steiger, M. Stolarski, M. Sulc, R. Sulej, H. Suzuki, A. Szabeleski, T. Szameitat, P. Sznajder, S. Takekawa, J. ter Wolbeek, S. Tessaro, F. Tessarotto, F. Thibaud, S. Uhl, I. Uman, M. Vandenbroucke, M. Virius, J. Vondra, L. Wang, T. Weisrock, M. Wilfert, R. Windmolders, W. Wislicki, H. Wollny, K. Zaremba, M. Zavertyaev, E. Zemlyanichkina, M. Ziembicki
A measurement of the azimuthal asymmetry in dihadron production in deep-inelastic scattering of muons on transversely polarised proton (NH$_{3}$) targets are presented. They provide independent access to the transversity distribution functions through the measurement of the Collins asymmetry in single hadron production. The data were taken in the year $2010$ with the COMPASS spectrometer using a $160\,\mbox{GeV}/c$ muon beam of the CERN SPS, increasing by a factor of about three the available statistics of the previously published data taken in the year $2007$. The measured sizeable asymmetry is in good agreement with the published data. An approximate equality of the Collins asymmetry and the dihadron asymmetry is observed, suggesting a common physical mechanism in the underlying fragmentation.
Transverse Momentum Dependent (TMD) dihadron production, including vector meson production, allows access to various TMD distribution and fragmentation functions. Dihadron production is complementary to single hadron semi-inclusive DIS measurements, pairing the same distribution functions with different fragmentation functions. While dihadrons present unique measurement opportunities, the TMD dihadron cross section is significantly more complex than that for single hadron production, due to the polarization in the final state. Various theoretical advances, which further clarify the complexity,…
Azimuthal correlations in two hadron production in deep inelastic scattering of unpolarized leptons off transversely polarized nucleon are discussed. Specifically, a simple approach for accessing ratios of structure functions corresponding to Sivers effect and transversity induced single spin azimuthal asymmetries to unpolarized structure functions is presented. This approach is then applied to a sample pseudo-data generated by a modified version of the LEPTO Monte Carlo event generator that includes the Sivers effect. Using this data it is shown, that the azimuthal correlations in the Sivers-…
We present a study on the double longitudinal-spin asymmetry of dihadron production in semi-inclusive deep inelastic scattering, in which the total transverse momentum of the final-state hadron pairs is integrated out. In particular, we investigate the origin of the $\cosϕ_R$ azimuthal asymmetry for which we take into account the coupling of the helicity distribution $g_1$ and the twist-3 dihadron fragmentation function $\widetilde{D}^{\sphericalangle}$. We calculate the $s$-wave and $p$-wave interference term $\widetilde{D}^{\sphericalangle}_{ot}$ in a spectator model. We estimate the $\cosϕ_…
We present an updated extraction of the transversity parton distribution based on the analysis of pion-pair production in deep-inelastic scattering off transversely polarized targets in collinear factorization. Data for proton and deuteron targets make it possible to perform a flavor separation of the valence components of the transversity distribution, using di-hadron fragmentation functions taken from the semi-inclusive production of two pion pairs in back-to-back jets in e+e- annihilation. The e+e- data from Belle have been reanalyzed using the replica method and a more realistic estimate o…
We study the single longitudinal-spin asymmetry of dihadron production in semi-inclusive deep inelastic scattering process. We consider the collinear picture in which the transverse momentum of the final-state hadron pair is integrated out, such that the $\sin ϕ_R$ azimuthal asymmetry arises from the coupling $h_L\, H_{1}^{\sphericalangle}$ as well as the coupling $g_1 \,\widetilde{G}^{\sphericalangle}$. We calculate the unknown twist-3 dihadron fragmentation function $\widetilde{G}^{\sphericalangle}$ using a spectator model which is successful in describing the dihadron production in the unpo…
The Sivers effect describes the correlation of the unpolarized parton's transverse momentum with the transverse spin of the nucleon. It manifests as a sine modulation of the cross section for single hadron semi-inclusive deep inelastic scattering (SIDIS) on a transversely polarized nucleon with the azimuthal angle between the produced hadron's transverse momentum and the nucleon spin ($φ_h$ and $φ_S$, respectively). It has been recently suggested that the Sivers effect can also be measured in two hadron SIDIS process as sine modulations involving the azimuthal angles $φ_T$ and $φ_R$ of both th…
Spin asymmetries provide a wide range of insights into nucleon structure and hadronization. Recent measurements of beam spin asymmetries of $π^+π^-$ dihadrons from Semi-Inclusive Deep Inelastic Scattering (SIDIS) at CLAS12 provide the first empirical evidence of a nonzero $G_1^\perp$, the parton helicity-dependent Dihadron Fragmentation Function (DiFF) encoding spin-momentum correlations in hadronization. These measurements have been extended to aid in the characterization of $H_1^\perp$ and $H_1^\sphericalangle$, the DiFFs dependent on parton transverse spin, via a multidimensional partial wa…
The analysis of semi-inclusive data from deep inelastic scattering of polarized muons off polarized protons and deuterons by the SMC is presented. The resulting charged hadron asymmetries are used to determine polarized valence and sea quark distributions and their contributions to the nucleon spin. In addition, a new approach to derive inclusive asymmetries is discussed.
The $T$-odd distribution functions contributing to transversity properties of the nucleon and their role in fueling nontrivial contributions to azimuthal asymmetries in semi-inclusive deep inelastic scattering are investigated. We use a dynamical model to evaluate these quantities in terms of HERMES kinematics.
We have updated our extraction of the transversity parton distribution based on the analysis of pion-pair production in deep-inelastic scattering off transversely polarized targets in collinear factorization. The most recent COMPASS data for proton and deuteron targets, complemented by previous HERMES data on the proton, make it possible to perform a flavor separation of the valence components of the transversity distribution, using di-hadron fragmentation functions taken from the semi-inclusive production of two pion pairs in back-to-back jets in $e^+ e^-$ annihilation. The $e^+ e^-$ data fro…
A new combined next to leading order QCD analysis of the polarized inclusive and semi-inclusive deep inelastic lepton-hadron scattering (DIS) data is presented. In contrast to previous combined analyses, the $1/Q^2$ terms (kinematic - target mass corrections, and dynamic - higher twist corrections) in the expression for the nucleon spin structure function $g_1$ are taken into account. The new COMPASS data are included in the analysis. The impact of the semi-inclusive data on the polarized parton densities (PDFs) and on the higher twist corrections is discussed. The new results for the PDFs are…
Semi-inclusive deep-inelastic scattering (SIDIS) at the Electron-Ion Collider will allow for precise mapping of the 3D momentum and spin structure of nucleons and nuclei over a large kinematic region. In this contribution, we demonstrate methods utilizing the hadronic final state and scattered electron, as well as machine learning, to more reliably reconstruct the virtual photon four momentum and SIDIS kinematics across the inclusive DIS coverage at the EIC.
We present preliminary results for an updated extraction of the transversity parton distribution based on the analysis of pion-pair production in deep-inelastic scattering off transversely polarized targets in collinear factorization. Data for proton and deuteron targets by HERMES and COMPASS allow for a flavor separation of the valence components of transversity, while di-hadron fragmentation functions are taken from the semi-inclusive production of two pion pairs in back-to-back jets in $e^+ e^-$ annihilation. The latter data from Belle have been reanalyzed using the replica method and a mor…
Helicity-dependent parton distribution functions at next-to-next-to-leading order accuracy from inclusive and semi-inclusive deep-inelastic scattering data
We calculate the cross section of J/psi plus jet associated production in ep deep-inelastic scattering within the factorization formalism of nonrelativistic quantum chromodynamics. Our analytic results disagree with previous analyses, both for the colour-singlet and colour-octet channels. Our theoretical predictions agree reasonably well with recent data taken by the H1 Collaboration at DESY HERA, significantly better than those obtained within the colour-singlet model.
We study the next-to-leading order perturbative QCD corrections to the transverse momentum-weighted Sivers asymmetry in semi-inclusive hadron production in lepton-proton deep inelastic scattering. The corresponding differential cross section is evaluated as a convolution of a twist-three quark-gluon correlation function, often referred to as Qiu-Sterman function, the usual unpolarized fragmentation function, and a hard coefficient function. By studying the collinear divergence structure, we identify the evolution kernel for the Qiu-Sterman function. The hard coefficient function, which is fini…
We analyse the role of partonic transverse motion in unpolarized Semi-Inclusive Deep Inelastic Scattering (SIDIS) processes. Imposing appropriate kinematical conditions, we find some constraints which fix an upper limit to the range of allowed k_perp values. We show that, applying these additional requirements on the partonic kinematics, we obtain different results with respect to the usual phenomenological approach based on the Gaussian smearing with analytical integration over an unlimited range of k_perp values. These variations are particularly interesting for some observables, like the < …
Inclusive hadron production in $e^+e^-$ annihilation has long been used to study both single hadron fragmentation functions (FF) and dihadron fragmentation functions (DiFF). In particular, the polarized DiFFs can be accessed in electron-positron annihilation by measuring azimuthal correlations between two back-to-back pairs of hadrons in the center of mass system, where the relevant structure functions can be expressed as convolutions of two (polarized) DiFFs. Here we explore the advantages of measuring the inclusive back-to-back production of a single hadron on one side against a hadron pair …
We study the production of polarized $Λ$ hyperon in semi-inclusive deep inelastic scattering off an unpolarized target. We include the cases in which the $Λ$ hyperon is longitudinally polarized or transversely polarized, and in which the lepton beam is unpolarized or longitudinally polarized. Within the framework of the transverse momentum dependent factorization, we take into account the complete decomposition of the parton correlator for fragmentation up to twist-3. We present the cross section of the process to order $1/Q$. The expressions of the polarized structure functions, which may giv…
The single spin asymmetries for a longitudinally polarized lepton beam or a longitudinally polarized nucleon target in semi-inclusive deep-inelastic scattering are twist-3 observables. We study these asymmetries in a simple diquark spectator model of the nucleon. Analogous to the case of transverse target polarization, non-vanishing asymmetries are generated by gluon exchange between the struck quark and the target system. It is pointed out that the coupling of the virtual photon to the diquark is needed in order to preserve electromagnetic gauge invariance at the twist-3 level. The calculatio…
We present a quantitative assessment of the impact a future Electron-Ion Collider would have in the determination of parton distribution functions in the proton and parton-to-hadron fragmentation functions through semi-inclusive deep-inelastic electron-proton scattering data. Specifically, we estimate the kinematic configurations for which the forthcoming data are expected to have the most significant impact in the precision of these distributions, computing the respective correlation and sensitivity coefficients. Implementing the reweighting technique over sets of simulated data with realisti…
We re-examine our previous calculation on the Collins effect in semi-inclusive deeply inelastic scattering (SIDIS) process with a $^3$He target, and find that our previous treatment on the dilution factors may cause the results larger than the realistic situation. We thus modify our calculation in an improved treatment with an updated prediction on the $\sin(ϕ_h+ϕ_S)$ asymmetry for the JLab 12 GeV under the transverse momentum dependent (TMD) factorization framework. Meanwhile, we also provide the prediction of such asymmetry for the JLab 6 GeV and the prediction of the $\sin(3ϕ_h-ϕ_S)$ asymme…
We survey the current phenomenological status of semi-inclusive deep inelastic scattering at moderate hard scales and in the limit of very large transverse momentum. As the transverse momentum becomes comparable to or larger than the overall hard scale, the differential cross sections should be calculable with fixed order pQCD methods, while small transverse momentum (TMD factorization) approximations should eventually break down. We find large disagreement between HERMES and COMPASS data and fixed order calculations done with modern parton densities, even in regions of kinematics where such c…
We analyze the left-right asymmetry of pion production in semi-inclusive deep inelastic scattering (SIDIS) process of unpolarized charged lepton on transversely polarized nucleon target. Unlike available treatments, in which some specific weighting functions are multiplied to separate theoretically motivated quantities, we do not introduce any weighting function following the analyzing method by the E704 experiment. The advantage is that this basic observable is free of any theoretical bias, although we can perform the calculation under the current theoretical framework. We present numerical c…
Impact of Future Dihadron Production Measurements on the Transversity Distributions and Tensor Charges of the Nucleon
Temple University（天普大学）；College of William & Mary（威廉玛丽学院）；Duke University（杜克大学）；Lebanon Valley College（黎巴谷学院）；Penn State University Berks（宾夕法尼亚州立大学伯克斯分校）；Jefferson Lab（杰斐逊实验室）
In inclusive deep-inelastic lepton-hadron scattering multi-photon exchange between the leptonic and the hadronic part of the process causes single spin asymmetries. The asymmetries exist for a polarized target as well as a polarized incoming or outgoing lepton, if the polarization vector has a component transverse with respect to the reaction plane. The spin dependent parts of the single polarized cross sections are suppressed like $α_{em} m_{pol}/Q$ - where $m_{pol}$ denotes the mass of the polarized particle - compared to the leading terms of the cross section for unpolarized or double-polar…
Dihadron azimuthal asymmetry and light-quark dipole moments at the Electron-Ion Collider
School of Physics, Peking University（北京大学物理学院）；Institute of High Energy Physics, Chinese Academy of Sciences（中国科学院高能物理研究所）；China Center of Advanced Science and Technology（中国科学技术大学北京校区）；Center for High Energy Physics, Peking University（北京大学高能物理中心）；Theory Center, Jefferson Lab（杰斐逊实验室理论中心）；High EnergyTheory Group, Physics Department,Brookhaven National Laboratory（布鲁克海文国家实验室物理系高能理论组）；Department of Physics and Astronomy, Michigan State University（密歇根州立大学物理与天文学系）
The spin-dependent cross sections for semi-inclusive lepton-nucleon scattering are derived in the framework of collinear factorization, including the effects of masses of the target and produced hadron at finite momentum transfer squared Q^2. At leading order the cross sections factorize into products of parton distribution and fragmentation functions evaluated in terms of new, mass-dependent scaling variables. The size of the hadron mass corrections is estimated at kinematics relevant for future semi-inclusive deep-inelastic scattering experiments.
We present an extraction of unpolarized transverse-momentum-dependent parton distribution and fragmentation functions based on more than two thousands data points from several experiments for two different processes: semi-inclusive deep-inelastic scattering and Drell-Yan production of lepton pairs. The baseline analysis is performed with a Monte Carlo replica method resumming large logarithms at N3LL accuracy. The resulting description of the data is very good ($χ^2/N_{\rm dat} = 1.06$). For semi-inclusive deep-inelastic scattering, predictions for multiplicities are normalized by factors that…
We derive mass corrections for semi-inclusive deep inelastic scattering of leptons from nucleons using a collinear factorization framework which incorporates the initial state mass of the target nucleon and the final state mass of the produced hadron. The formalism is constructed specifically to ensure that physical kinematic thresholds for the semi-inclusive process are explicitly respected. A systematic study of the kinematic dependencies of the mass corrections to semi-inclusive cross sections reveals that these are even larger than for inclusive structure functions, especially at very smal…
We report on the first extraction of interference fragmentation functions from the semi-inclusive production of two hadron pairs in back-to-back jets in e+e- annihilation. A nonzero asymmetry in the correlation of azimuthal orientations of opposite π+π- pairs is related to the transverse polarization of fragmenting quarks through a significant polarized dihadron fragmentation function. Extraction of the latter requires the knowledge of its unpolarized counterpart, the probability density for a quark to fragment in a π+π- pair. Since data for the unpolarized cross section are missing, we extrac…
We present a new proposal to study the helicity-dependent dihadron fragmentation functions (DiFF), which describe the correlations of the longitudinal polarization of a fragmenting quark with the transverse momenta of the produced hadron pair. Recent experimental searches for this DiFF via azimuthal asymmetries in back-to-back hadron pair production in $e^+e^-$ annihilation by the ${\tt BELLE}$ Collaboration did not yield a signal. Here we propose a new way to access this DiFF in $e^+e^-$ annihilation, motivated by the recently recalculated cross section of this reaction, which explains why th…
Azimuthal single-spin asymmetries (SSA) in semi-inclusive electroproduction of charged pions and kaons in deep-inelastic scattering of positrons on a transversely polarised hydrogen target were observed. SSA amplitudes for both the Collins and the Sivers mechanism are presented.
This contribution covers three recent results on deep-inelastic scattering at HERA: (i) new measurements of the proton longitudinal structure function $F_L$ from H1 and ZEUS experiments, (ii) a dedicated NC cross section measurement from ZEUS in the region of high Bjorken $x$, and (iii) preliminary combination results of all HERA inclusive data published up to now by H1 and ZEUS, taking into account the experimental correlations between measurements.
In 1995, the HERMES experiment at DESY (Hamburg, Germany) has taken its first data, using the 27.5 GeV polarised HERA positron beam impinging on a longitudinally polarised internal $^3$He target. Preliminary results from the semi-inclusive physics program are presented.
Single-spin asymmetries in the semi-inclusive production of charged pions in deep-inelastic scattering from transversely and longitudinally polarized proton targets are combined to evaluate the subleading-twist contribution to the longitudinal case. This contribution is significantly positive for (π^+) mesons and dominates the asymmetries on a longitudinally polarized target previously measured by \hermes. The subleading-twist contribution for (π^-) mesons is found to be small.
Recent results from the \emph{ep} collier HERA are presented. Inclusive dijet cross sections have been measured in neutral current deep inelastic scattering, for virtualities of the exchanged boson in the range $125 < Q^{2} < 20\,000\; GeV^{2}$ and in photoproduction, $Q^{2} \sim 0 GeV^{2}$. The measurements are compared to perturbative QCD calculations at next-to-leading order.
We calculate $g_{1T}$ and $h_{1L}^\perp$, two of the eight leading twist transverse momentum dependent parton distributions (TMDs), in the light-cone quark-diquark model. The new TMDs can be measured through semi-inclusive deep inelastic scattering (SIDIS). We present predictions of the single and double spin asymmetries related to $g_{1T}$ and $h_{1L}^\perp$ in SIDIS at HERMES, COMPASS, and JLab kinematics respectively.
Results are presented on the inclusive production of isolated prompt photons in deep inelastic scattering with a four-momentum transfer of $Q^2>4 GeV^2$. The cross sections are measured for the transverse momentum range of the photons $3 < E_T^γ< 10 GeV$ and for the pseudorapidity range of the photons $-1.2 < η^γ< 1.8$. They are measured differentially as a function of $E_T^γ$ and $η^γ$. The results are compared with the predictions of a leading order calculation, which is in reasonable agreement with the inclusive measurement.
A Jefferson Lab experiment proposal was discussed in this talk. The experiment is designed to measure the beam-target double-spin asymmetries $A_{1n}^h$ in semi-inclusive deep-inelastic $\vec n({\vec e}, e^\prime π^+)X$ and $\vec n({\vec e}, e^\prime π^-)X$ reactions on a longitudinally polarized $^3$He target. In addition to $A_{1n}^h$, the flavor non-singlet combination $A_{1n}^{π^+ - π^-}$, in which the gluons do not contribute, will be determined with high precision to extract $Δd_v(x)$ independent of the knowledge of the fragmentation functions. The data will also impose strong constraint…
We present the details of a new factorized approach to semi-inclusive deep-inelastic scattering which treats QED and QCD radiation on equal footing, and provides a systematically improvable approximation to the extraction of transverse momentum dependent parton distributions. We demonstrate how the QED contributions can be well approximated by collinear factorization, and illustrate the application of the factorized approach to QED radiation in inclusive scattering. For semi-inclusive processes, we show how radiation effects prevent a well-defined "photon-nucleon" frame, forcing one to use a t…
First measurements of the Collins and Sivers asymmetries of charged hadrons produced in deep-inelastic scattering of muons on a transversely polarized 6-LiD target are presented. The data were taken in 2002 with the COMPASS spectrometer using the muon beam of the CERN SPS at 160 GeV/c. The Collins asymmetry turns out to be compatible with zero, as does the measured Sivers asymmetry within the present statistical errors.
Inspired by a recent study of Iancu, Mueller and Triantafyllopoulos [1] and earlier papers by Golec-Biernat and Wusthoff [2,3], we propose semi-inclusive diffractive deep inelastic scattering (SIDDIS) to investigate the gluon tomography in the nucleon and nuclei at small-$x$. The relevant diffractive quark and gluon parton distribution functions (DPDF) can be computed in terms of the color dipole S-matrices in the fundamental and adjoint representations, respectively. Novel correlations from the gluon tomography in the dipole S-matrix can be experimentally studied through the DPDFs in these pr…
Double-spin asymmetries of semi-inclusive cross sections for the production of identified pions and kaons have been measured in deep-inelastic scattering of polarized positrons on a polarized deuterium target. Five helicity distributions including those for three sea quark flavors were extracted from these data together with re-analyzed previous data for identified pions from a hydrogen target. These distributions are consistent with zero for all three sea flavors. A recently predicted flavor asymmetry in the polarization of the light quark sea appears to be disfavored by the data.
Inclusive jet production is studied in neutral current deep-inelastic positron-proton scattering at large four momentum transfer squared Q^2>150 GeV^2 with the H1 detector at HERA. Single and double differential inclusive jet cross sections are measured as a function of Q^2 and of the transverse energy E_T of the jets in the Breit frame. The measurements are found to be well described by calculations at next-to-leading order in perturbative QCD. The running of the strong coupling is demonstrated and the value of alpha_s(M_Z) is determined. The ratio of the inclusive jet cross section to the in…
Polarized deep--inelastic scattering data on longitudinally polarized hydrogen and deuterium targets have been used to determine double spin asymmetries of cross sections. Inclusive and semi--inclusive asymmetries for the production of positive and negative pions from hydrogen were obtained in a re--analysis of previously published data. Inclusive and semi--inclusive asymmetries for the production of negative and positive pions and kaons were measured on a polarized deuterium target. The separate helicity densities for the up and down quarks and the anti--up, anti--down, and strange sea quarks…
We introduce a new phenomenological tool based on momentum region indicators to guide the analysis and interpretation of semi-inclusive deep-inelastic scattering measurements. The new tool, referred to as "affinity", is devised to help visualize and quantify the proximity of any experimental kinematic bin to a particular hadron production region, such as that associated with transverse momentum dependent factorization. We apply the affinity estimator to existing HERMES and COMPASS data and expected data from Jefferson Lab and the future Electron-Ion Collider. We also provide an interactive not…
The transfer of polarization from a high-energy positron to a \lam hyperon produced in semi-inclusive deep-inelastic scattering has been measured. The data have been obtained by the HERMES experiment at DESY using the 27.6 GeV longitudinally polarized positron beam of the HERA collider and unpolarized gas targets internal to the positron (electron) storage ring. The longitudinal spin transfer coefficient is found to be $\dll = 0.11 \pm 0.10 \mathrm{(stat)} \pm 0.03 \mathrm{(syst)}$ at an average fractional energy carried by the \lam hyperon $<z >= 0.45$. The dependence of \dll on both the frac…
The transverse-target single-spin asymmetry for inclusive deep-inelastic scattering with effectively unpolarized electron and positron beams off a transversely polarized hydrogen target was measured, with the goal of searching for a two-photon exchange signal in the kinematic range 0.007 < x_B < 0.9 and 0.25 GeV**2 < Q**2 < 20 GeV**2. In two separate regions Q**2 > 1 GeV**2 and Q**2 < 1 GeV**2, and for both electron and positron beams, the asymmetries are found to be consistent with zero within statistical and systematic uncertainties, which are of order 10**(-3) for the asymmetries integrated…
Spin asymmetries of semi-inclusive cross sections for the production of positively and negatively charged hadrons have been measured in deep-inelastic scattering of polarized positrons on polarized hydrogen and 3He targets, in the kinematic range 0.023<x<0.6 and 1 GeV^2<Q^2<10 GeV^2. Polarized quark distributions are extracted as a function of x for up $(u+u_bar) and down (d+d_bar) flavors. The up quark polarization is positive and the down quark polarization is negative in the measured range. The polarization of the sea is compatible with zero. The first moments of the polarized quark distrib…
The properties of jets produced in p+p collisions at sqrt(s)=200 GeV are measured using the method of two particle correlations. The trigger particle is a leading particle from a large transverse momentum jet while the associated particle comes from either the same jet or the away-side jet. Analysis of the angular width of the near-side peak in the correlation function determines the jet fragmentation transverse momentum j_T . The extracted value, sqrt(<j_T^2>)= 585 +/- 6(stat) +/- 15(sys) MeV/c, is constant with respect to the trigger particle transverse momentum, and comparable to the previo…
The flavor asymmetry of the light quark sea of the nucleon is determined in the kinematic range 0.02<x<0.3 and 1 GeV^2<Q^2<10 GeV^2, for the first time from semi-inclusive deep-inelastic scattering. The quantity (dbar(x)-ubar(x))/(u(x)-d(x)) is derived from a relationship between the yields of positive and negative pions from unpolarized hydrogen and deuterium targets. The flavor asymmetry dbar-ubar is found to be non-zero and x dependent, showing an excess of dbar over ubar quarks in the proton.
