High Energy Spin Physics Research Articles

Twist-3 gluon fragmentation contribution to polarized hyperon production in unpolarized proton-proton collision

Understanding the origin and mechanism of the transverse polarization of hyperons produced in unpolarized proton-proton collision, $pp\to \Lambda^\uparrow X$, has been one of the long-standing issues in high-energy spin physics. In the framework of the collinear factorization applicable to large-$p_T$ hadron productions, this phenomenon is a twist-3 observable which is caused by multi-parton correlations either in the initial protons or in the process of fragmentation into the hyperon. We derive the twist-3 gluon fragmentation function (FF) contribution to this process in the leading order (LO) with respect to the QCD coupling constant. Combined with the known results for the contribution from the twist-3 distribution function and the twist-3 quark FF, this completes the LO twist-3 cross section. We also found that the model independent relations among the twist-3 gluon FFs based on the QCD equation of motion and the Lorentz invariance property of the correlation functions guarantee the color gauge invariance and the frame-independence of the cross section.

XVII Workshop on High Energy Spin Physics “DSPIN-2017”

Preface17th Workshop on High Energy Spin Physics was a continuation of the series of workshops, started in Dubna in 1981 due to the initiative of the prominent theorist Lev Iosifovich Lapidus. Since than, such workshops are taking place in Dubna or Protvino each odd year, between Spin Physics. These workshops provide an opportunity to discuss the news of the respective year. From the other side, their important specifics was the possibility of participation of the numerous participants from Former Soviet Union and Eastern Europe countries, for which the long travels may be difficult due to financial (and earlier also bureaucratic) reasons.There were more than 100 participants from Russia, Germany, Czech Republic, Italy, Poland, Slovakia, USA, Armenia, Bulgaria, Estonia, Netherlands, Great Britain. The last years brought many new experimental results, starting from the Higgs boson discovery at LHC. In the talk of I. Ginzburg (Novosibirsk) the two-doublet Higgs model was considered focusing on the C and P symmetries important for spin physics. The theoretical possibilities of new particles production and searches at LHC and future ILC were considered in the talks of A. Pankov and A. Tsytrinov from Gomel.

Theoretical estimate on tensor-polarization asymmetry in proton-deuteron Drell-Yan process

Tensor-polarized parton distribution functions are new quantities in spin-one hadrons such as the deuteron, and they could probe new quark-gluon dynamics in hadron and nuclear physics. In charged-lepton deep inelastic scattering (DIS), they are studied by the twist-two structure functions $b_1$ and $b_2$. The HERMES collaboration found unexpectedly large $b_1$ values than a naive theoretical expectation based on the standard deuteron model. The situation should be significantly improved in the near future by an approved experiment to measure $b_1$ at JLab (Thomas Jefferson National Accelerator Facility). There is also an interesting indication in the HERMES result that finite antiquark tensor polarization exists. It could play an important role in solving a mechanism on tensor structure in the quark-gluon level. The tensor-polarized antiquark distributions are not easily determined from the charged-lepton DIS; however, they can be measured in a proton-deuteron Drell-Yan process with a tensor-polarized deuteron target. In this article, we estimate the tensor-polarization asymmetry for a possible Fermilab Main-Injector experiment by using optimum tensor-polarized PDFs to explain the HERMES measurement. We find that the asymmetry is typically a few percent. If it is measured, it could probe new hadron physics, and such studies could create an interesting field of high-energy spin physics. In addition, we find that a significant tensor-polarized gluon distribution should exist due to $Q^2$ evolution, even if it were zero at a low $Q^2$ scale. The tensor-polarized gluon distribution has never been observed, so that it is an interesting future project.

An Analytical Review of DSPIN-13

A short review of the XV Workshop on High Energy Spin Physics (Dubna, Russia, October 8–12, 2013) is presented.

Symposium Summary

The Stern-Gerlach experiment and the origin of electron spin are described in historical context. SPIN 2014 occurs on the fortieth anniversary of the first International High Energy Spin Physics Symposium at Argonne in 1974. A brief history of the international spin conference series is presented.

Dawn of High Energy Spin Physics — In Memory of Michel Borghini

High energy spin physics with the polarized proton target in 1960s is shown. The dynamic polarization in which the electronic polarization is transferred to protons in paramagnetic material by means of magnetic coupling was proposed at the beginning of 1960s. The first N-N experiment using a polarized proton target was performed with the crystal of La[Formula: see text]Mg[Formula: see text] (NO[Formula: see text]24H[Formula: see text]O at CEN-Saclay and Berkeley in 1962, followed by [Formula: see text]-p experiments in several laboratories. Protons in organic materials were found to be polarized up to 80% in [Formula: see text]He cryostats in 1969. It was helpful for large background experiments. High proton polarization was interpreted in the spin temperature theory. Spin frozen targets were constructed in early 1970s and used for experiments which require wide access angle. Michel Borghini was a main player for almost all the above works.

Future Prospects of di-jet Production Constraining Δg(x) at Low x in Polarized p + p Collisions at RHIC

One of the main objectives of the high-energy spin physics program at RHIC at BNL is the precise determination of the polarized gluon distribution function, Δg(x). Polarized [Formula: see text] collisions at [Formula: see text] GeV and at [Formula: see text] GeV at RHIC provide an unique way to probe the proton spin structure. Inclusive measurements, such as inclusive jet and hadron production, have so far been the prime focus of various results at [Formula: see text] GeV constraining Δg(x) for 0.05 < x < 0.2. A recent global analysis provides for the first time evidence of a non-zero value of the gluon polarization [Formula: see text]. First results of di-jet production at [Formula: see text] GeV by the STAR collaboration will allow a better constraint of the underlying event kinematics. Extending the current program to smaller values of x is a key goal for the future high-energy spin physics program at RHIC. Forward di-jet production measurements at STAR beyond the current acceptance from -1 < η < +2 to +2.5 < η < +4, in particular those carried out at [Formula: see text] GeV, provides access to low x values at the level of 10-3 where current uncertainties of Δg(x) remain very large. Those measurements will eventually be complemented by a future Electron-Ion Collider facility probing Δg(x) in polarized [Formula: see text] collisions.

Recent results of gluon and sea quark polarization measurements in polarized proton-proton collisions at STAR

The STAR experiment at RHIC is carrying out a comprehensive high-energy spin physics program to understand the internal structure and dynamics of the proton in polarized proton-proton collisions at = 200 GeV and = 500/510 GeV. STAR has the capability, with nearly full azimuthal coverage, to reconstruct leptons, hadrons and jets in the mid-rapidity region (|η| < 1). The results for inclusive jet longitudinal double spin asymmetries taken during the 2009 RHIC run indicate the first non-zero gluon contribution (Δg(x,Q2)/g(x,Q2)) to the proton spin for 0.05 < x < 1 (Bjorken-x: momentum fraction of partons). Recent longitudinal single-spin asymmetry measurements of W+/− bosons at = 500/510 GeV in polarized proton-proton collisions provide a direct probe of the polarized anti-u and anti-d quark distributions (Δū(x, Q2), Δd̄(x, Q2)). These results better constrain the polarized gluon and sea quark distributions of the proton in the RHIC sensitive kinematic region. Future measurements with continuing high energy polarized proton-proton run at RHIC and detector upgrade will explore the gluonic contribution to the proton spin in extended range.

Summary of the XIII Workshop on High Energy Spin Physics

The XIII Workshop on High Energy Spin Physics (DSPIN-09) continued a series of similar meetings, the first of which took place 29 years ago. The workshop gave a chance to present and discuss the news collected during he past year. Many fresh experimental, theoretical and technical results of this branch of physics were presented. Some of them were reported and discussed for the first time just at this meeting. A number of talks were devoted to future experiments at the Large Hadron Collider (LHC) at CERN, to interesting possibilities of the polarized photon beams at the International Linear Collider (ILC), and to the spin program of the accelerator complex NICA at JINR. The Workshop was dedicated to the memory of Yan Pawel Nassalski.

Tensor-polarized quark and antiquark distribution functions in a spin-one hadron

To understand orbital-angular-momentum contributions is becoming crucial for clarifying nucleon-spin issue in the parton level. Twist-two structure functions b_1 and b_2 for spin-one hadrons could probe orbital-angular-momentum effects, which reflect a different aspect from current studies for the spin-1/2 nucleon, since they should vanish if internal constituents are in the S state. These structure functions are related to tensor structure in spin-one hadrons. Studies of such tensor structure will open a new field of high-energy spin physics. The structure functions b_1 and b_2 are described by tensor-polarized quark and antiquark distributions delta_T-q and delta_T-qbar. Using HERMES data on the b_1 structure function for the deuteron, we made an analysis of extracting the distributions delta_T-q and delta_T-qbar in a simple x-dependent functional form. Optimum distributions are proposed for the tensor-polarized valence and antiquark distribution functions from the analysis. A finite tensor polarization is obtained for antiquarks if we impose a constraint that the first moments of tensor-polarized valence-quark distributions vanish. It is interesting to investigate a physics mechanism to create a finite tensor-polarized antiquark distribution.

Prospects for triggering in experiment PAX at GSI

In experiment PAX, proposed for the new accelerator complex at GSI, investigations in the field of high-energy spin physics with the use of a polarized antiproton beam are planned. In this paper the possibilities for triggering are considered taking into account the PAX detector properties and a probable configuration of the trigger system is discussed for the first time.

Program of the 3rd Circum-Pan-Pacific Symposium on "HIGH ENERGY SPIN PHYSICS" October 8–13, 2001, Beijing, China

International Journal of Modern Physics AVol. 18, No. 08, pp. vii-xii (2003) SPECIAL ISSUE: Proceedings of the 3rd Circum-Pan-Pacific Symposium on High Energy Spin Physics, Peking University, Beijing, China, 8–13 October, 2001; Editors: Bo-Qiang Ma and Kuang-Ta ChaoNo AccessProgram of the 3rd Circum-Pan-Pacific Symposium on "HIGH ENERGY SPIN PHYSICS" October 8–13, 2001, Beijing, Chinahttps://doi.org/10.1142/S0217751X03015052Cited by:0 PreviousNext AboutSectionsPDF/EPUB ToolsAdd to favoritesDownload CitationsTrack CitationsRecommend to Library ShareShare onFacebookTwitterLinked InRedditEmail You currently do not have access to the full text article. Recommend the journal to your library today! FiguresReferencesRelatedDetails Recommended Vol. 18, No. 08 Metrics History PDF download

Committees of the 3rd Circum-Pan-Pacific Symposium on HIGH ENERGY SPIN PHYSICS

Committees of the 3rd Circum-Pan-Pacific Symposium on HIGH ENERGY SPIN PHYSICS

OPEN QUESTIONS IN HIGH ENERGY SPIN PHYSICS

I describe a few of the most exciting open questions in high energy spin physics. After a brief look at (g - 2)μ and the muon electric dipole moment, I concentrate on QCD spin physics. Pressing questions include the interpretation of new asymmetries seen in semi-inclusive DIS, measuring the polarized gluon and quark transversity distributions in the nucleon, testing the DHGHY Sum Rule, measuring the orbital angular momentum in the nucleon, and many others which go beyond the space and time allotted for this talk.

STATUS OF SPIN PHYSICS: EXPERIMENTAL SUMMARY

The current status of spin physics experiments, based on talks presented at the Third Circum-Pan-Pacific Symposium on High Energy Spin Physics held in Beijing, 2001, is summarized in this article. Highlights of recent experimental results at SLAC, JLab, and DESY, as well as future plans at these facilities and at RHIC-spin are discussed.

SINGLE SPIN ASYMMETRIES IN INCLUSIVE HIGH ENERGY HADRON–HADRON COLLISION PROCESSES

It has been realized for quite a long time that single-spin experiments, in which one of the colliding objects is transversely polarized, can be helpful in studying the properties of strong interaction in general and in testing quantum chromodynamics (QCD) in particular. Striking effects have been observed in the past few years which deviate drastically from the expectation of the perturbative QCD parton model. These effects have received much attention. New experiments of the similar type are underway and/or planned. Different theoretical attempts have been made to understand these effects. In this review, the special role played by singly polarized high-energy hadron–hadron collisions in high energy spin physics is emphasized. Characteristics of the available data for inclusive hadron productions are briefly summarized. Different theoretical approaches for such processes are reviewed with special attention to a nonperturbative model which explicitly takes the orbital motion of the valence quarks and hadronic surface effects into account. The connection between such asymmetries and hyperon polarization in unpolarized reactions is discussed. An example of the possible application of such experimental results in other processes is given.

The JINR source of polarized deuterons, polaris. Operation and improvement

For the last years an intensive study of polarization phenomena in high energy spin physics was carried out at the Dubna 10 GeV accelerator using polarized deuteron beam. The commissioning of the new superconducting accelerator NUCLOTRON supposes to continue the polarization program. A short review of the source of polarized deuterons POLARIS at the Laboratory of High Energies (JINR) is presented.

Status of spin physics

This is a slightly updated summary of the new results which were presented at the 13th International Symposium on High Energy Spin Physics, that was held at IHEP-Protvino during 7–12, September 1998. I subdivided the results into the topics of: spin physics history; polarized beams and Siberian snakes; polarized targets, jets and sources; nucleon structure function experiments; electro-weak spin experiments; hadronic spin experiments; spin theory; and finally future polarized beam facilities.

Structure functions in the polarized Drell-Yan processes with spin-1/2 and spin-1 hadrons. I. General formalism

We discuss general formalism for the structure functions which can be investigated in the polarized Drell-Yan processes with spin-1/2 and spin-1 hadrons. To be specific, the formalism can be applied to the proton-deuteron Drell-Yan processes. Because of the spin-1 nature, there are new structure functions which cannot be studied in the proton-proton reactions. Imposing Hermiticity, parity conservation, and time-reversal invariance, we find that 108 structure functions exist in the Drell-Yan processes. However, the number reduces to 22 after integrating the cross section over the virtual-photon transverse momentum Q_T or after taking the limit Q_T->0. There are 11 new structure functions in addition to the 11 ones in the Drell-Yan processes of spin-1/2 hadrons. The additional structure functions are associated with the tensor structure of the spin-1 hadron, and they could be measured by quadrupole spin asymmetries. For example, the structure functions exist for "intermediate" polarization although their contributions vanish in the longitudinal and transverse polarization reactions. We show a number of spin asymmetries for extracting the polarized structure functions. The proton-deuteron reaction may be realized in the RHIC-Spin project and other future ones, and it could be a new direction of next generation high-energy spin physics.

Spin physics at RHIC

The acceleration and collision of polarized proton beam is scheduled at RHIC to carry out the high energy spin physics such as the spin structure of nucleon. The overview of the RHIC spin collider and physics prospect is presented.