36678859
Semi-inclusive DIS: Factorization
Semi-inclusive DIS: Factorization Feng Yuan 1,2 1- Nuclear Science Division, Lawrence Berkeley National Laboratory, Berkeley, CA 94720, USA 2- RIKEN BNL Research Center, Brookhaven National Laboratory, Upton, NY 11973, USA In this talk, we will present a QCD factorization theorem for the semi-inclusive deep- inelastic scattering with hadrons in the current fragmentation region detected at low transverse momentum. There has been considerable experimental and theoretical interest in semi-inclusive hadron production in deep inelastic scattering (SIDIS) processes. For example, by studying the polarized and unpolarized SIDIS, one will be able to identify the sea quark distribution and polarization in nucleon, and the experimental results from the HERMES collabora- tion have revealed nontrivial sea structure in nucleon [1]. More recently, SIDIS opened a new window to study the transverse momentum dependent (TMD) parton distributions and fragmentation functions from the low transverse momentum hadron production. The trans- verse momentum distribution of the ﬁnal state hadron is directly related to the transverse momentum dependence of the parton distributions and fragmentation. These studies will provide new opportunities to explore the partonic structure of nucleon, especially the three- dimension distribution of partons inside nucleon. The DIS experiments, including HERMES, COMPAS, and JLab Hall B collaborations, have studied various azimuthal asymmetries in SIDIS. In particular, the HERMES collaboration found sizable single spin asymmetries in these processes involving nontrivial QCD eﬀects and hadron structure. On the theory side, there has been great progress in the last few years too. In this short talk, it is impossible to cover all these important physics. Rather, I would like to focus on one of the questions concerning applying the QCD to the description of the semi-inclusive DIS, in particular, the QCD factorization for SIDIS. Unlike the inclusive DIS process, SIDIS is more involved because of additional hadron measurement in the ﬁnal state. We can classify the SIDIS processes into three diﬀerent categories. First, if we integrate out the transverse momentum of the ﬁnal state hadron, these SIDIS will be similar to the inclusive DIS, and a collinear factorization is applicable. The cross section can be written as a convolution of the integrated parton distribution and fragmentation function and the hard partonic cross section which can be calculated from perturbative QCD. Second class is the large trans- verse momentum SIDIS. When transverse momentum is large enough (in order of Q, the virtuality of the virtual photon), again a collinear factorization shall be used to analyze the cross section. The third class is the low transverse momentum hadron production, where a collinear factorization approach may not be applicable because the transverse momentum of the ﬁnal state hadron is small compared to the hard scale Q. In order to describe this class of processes, we have to introduce a new factorization theorem, involving the transverse momentum dependent parton distribution and fragmentation functions. Rigorous theoret- ical studies in this direction started from the classical work on semi-inclusive processes in e + e − annihilation by Collins and Soper [2], where a QCD factorization was proved, and ∗ This work was supported in part by the U.S. Department of Energy under contract DE-AC02- 05CH11231. We are grateful to RIKEN, Brookhaven National Laboratory and the U.S. Department of Energy (contract number DE-AC02-98CH10886) for providing the facilities essential for the completion of this work. DIS 2008
86866677
Single spin asymmetry scaling in the forward rapidity region at RHIC
We investigate the scaling properties in inclusive hadron production and the associated single transverse spin asymmetry in the forward rapidity region at RHIC. We find that the spin-averaged experimental data in both pp and dAu collisions demonstrates a transverse-momentum-dependent geometric scaling. We introduce the transverse-momentum-dependent Collins fragmentation function to study the scaling of the single transverse spin asymmetries. The general feature of the scaling analysis is consistent with the experimental observations, in particular, for the transverse momentum dependence of the spin asymmetries at RHIC energy. We further propose to probe the saturation scale of nuclei by measuring the spin asymmetry normalized by that in pp scattering at low transverse momentum.
9899757
Probing parton orbital angular momentum in longitudinally polarized nucleon
While the total orbital angular momentum (OAM) of a definite quark flavor in a longitudinally-polarized nucleon can be obtained through a sum rule involving twist-two generalized parton distribution (GPDs), its distribution as a function of parton momentum in light-front coordinates is more complicated to define and measure because it involves intrinsically twist-three effects. In this paper, we consider two different parton OAM distributions. The first is manifestly gauge invariant, and its moments are local operators and calculable in lattice QCD. We show that it can potentially be measured through twist-three GPDs. The second is the much-debated canonical OAM distribution natural in free-field theory and light-cone gauge. We show the latter in light-cone gauge can also be related to twist-three GPDs as well as quantum phase-space Wigner distributions, both being measurable in high-energy experiments.
124142460
High-$p_T$ $\psi\psi$ production as strong signals for Double Parton scattering at the Tevatron
54724455
Theoretical Overview on Recent Developments in Transverse Spin Physics
Transverse-spin physics has been very active and rapidly developing in the last few years. In this talk, I will briefly summarize recent theoretical developments, focusing on the associated QCD dynamics in transverse spin physics.
118319655
Polarized $J/\psi$ production in deep inelastic scattering at HERA
We perform a calculation on the polarization of J/psi production in deep inelastic scattering in the HERA energy range. For the inclusive production distributions, we find that the color-singlet contributions are consistent with the experimental data in the major region of z (z>0.4). Only in low z regions, there are some hints of the need of the color-octet contributions to describe the experimental data. For the polarization of J/psi in DIS processes, we find the parameter alpha changes with Q^2. Especially, at higher Q^2, difference on alpha between color-singlet and color-octet contributions become more distinctive. In the two regions of lower and larger z, the polarization parameter alpha have different features. These properties can provide important information on the polarization mechanism for J/psi production.
118602952
Hidden conformal symmetry of extremal Kaluza-Klein black hole in four dimensions
We study the hidden conformal symmetry of four-dimensional extremal Kaluza-Klein black hole. The scalar Laplacian corresponding to the radial equation in the near-region is rewritten in terms of the $ {\text{SL}}\left( {2,\mathbb{R}} \right) $ quadratic Casimir. Using the first law of black hole thermodynamics, this symmetry enables us to obtain the conjugate charges for the CFT side. The real-time correlators are also found to agree with the CFT expectations.
118374860
Real-time Detection and Rapid Multiwavelength Follow-up Observations of a Highly Subluminous Type II-P Supernova from the Palomar Transient Factory Survey
The Palomar Transient Factory (PTF) is an optical wide-field variability survey carried out using a camera with a 7.8 deg^2 field of view mounted on the 48 inch Oschin Schmidt telescope at Palomar Observatory. One of the key goals of this survey is to conduct high-cadence monitoring of the sky in order to detect optical transient sources shortly after they occur. Here, we describe the real-time capabilities of the PTF and our related rapid multiwavelength follow-up programs, extending from the radio to the γ-ray bands. We present as a case study observations of the optical transient PTF10vdl (SN 2010id), revealed to be a very young core-collapse (Type II-P) supernova having a remarkably low luminosity. Our results demonstrate that the PTF now provides for optical transients the real-time discovery and rapid-response follow-up capabilities previously reserved only for high-energy transients like gamma-ray bursts.
119293239
Harrison Metrics for the Schwarzschild Black Hole
Based on the hidden conformal symmetry, some authors have proposed a Harrison metric for the Schwarzschild black hole. We give a procedure which can generate a family of Harrison metrics starting from a general set of SL(2, R) vector fields. By analogy with the subtracted geometry of the Kerr black hole, we find a new Harrison metric for the Schwarzschild case. Its conformal generators are also investigated using the Killing equations in the near-horizon limit.
119100083
A modified variational principle for gravity in the modified Weyl geometry
The usual interpretation of the Weyl geometry is modified in two senses. First, both the additive Weyl connection and its variation are treated as (1, 2) tensors under the action of the Weyl covariant derivative. Second, a modified covariant derivative operator is introduced which still preserves the tensor structure of the theory. With its help, the Riemann tensor in the Weyl geometry can be written in a more compact form. We justify this modification in detail from several aspects and obtain some insights along the way. By introducing some new transformation rules for the variation of tensors under the action of the Weyl covariant derivative, we find a Weyl version of the Palatini identity for the Riemann tensor. To derive the energy–momentum tensor and equations of motion for gravity in the Weyl geometry, one naturally applies this identity at first, and then converts the variation of the additive Weyl connection to those of the metric tensor and Weyl gauge field. We also discuss possible connections to the current literature on the Weyl-invariant extension of massive gravity and the variational principles in f(R) gravity.