29 research outputs found
Single Inclusive Jet Production in Collisions at NLO in the small- regime
We present the first complete NLO prediction with full jet algorithm
implementation for the single inclusive jet production in collisions
within the CGC effective theory. Our prediction is fully differential over the
final state physical kinematics, which allows the implementation of any IR safe
observable including the jet clustering procedure. The NLO calculation is
organized with the aid of the power counting proposed in [1] which gives rise
to the novel soft contributions in the CGC factorization. We achieve the
fully-differential calculation by constructing suitable subtraction terms to
handle the singularities in the real corrections. The subtraction contributions
can be exactly integrated analytically. We present the NLO cross section with
the jets constructed using the anti- algorithm. The NLO calculation
demonstrates explicitly the validity of the CGC factorization in jet
production. Furthermore, as a byproduct of the subtraction method, we also
derive the fully analytic cross section for the forward jet production in the
small- limit. We show that in the small- approximation, the forward jet
cross section can be factorized into a semi-hard cross section that produces a
parton and the semi-inclusive jet functions. We argue that this feature holds
for generic jet production and jet substructure observables in the CGC
framework. Last, we show numerical analyses of the derived formula to validate
our calculations. We justify when the small- approximation is appropriate.
Like forward hadron production, the obtained NLO result also exhibits the
negativity of the cross section in the large jet transverse regime, which
signals the need for the threshold resummation. A sketch of the threshold
resummation in the CGC framework is presented based on the multiple emission
picture.Comment: 67 pages, multiple figures, comments welcome, reference update
The RHIC Spin Program: Achievements and Future Opportunities
This document summarizes recent achievements of the RHIC spin program and
their impact on our understanding of the nucleon's spin structure, i.e. the
individual parton (quark and gluon) contributions to the helicity structure of
the nucleon and to understand the origin of the transverse spin phenomena. Open
questions are identified and a suite of future measurements with polarized
beams at RHIC to address them is laid out. Machine and detector requirements
and upgrades are briefly discussed
The RHIC SPIN Program: Achievements and Future Opportunities
Time and again, spin has been a key element in the exploration of fundamental
physics. Spin-dependent observables have often revealed deficits in the assumed
theoretical framework and have led to novel developments and concepts. Spin is
exploited in many parity-violating experiments searching for physics beyond the
Standard Model or studying the nature of nucleon-nucleon forces. The RHIC spin
program plays a special role in this grand scheme: it uses spin to study how a
complex many-body system such as the proton arises from the dynamics of QCD.
Many exciting results from RHIC spin have emerged to date, most of them from
RHIC running after the 2007 Long Range Plan. In this document we present
highlights from the RHIC program to date and lay out the roadmap for the
significant advances that are possible with future RHIC running
Intramolecular Folding in Human ILPR Fragment with Three C-Rich Repeats
Enrichment of four tandem repeats of guanine (G) rich and cytosine (C) rich sequences in functionally important regions of human genome forebodes the biological implications of four-stranded DNA structures, such as G-quadruplex and i-motif, that can form in these sequences. However, there have been few reports on the intramolecular formation of non-B DNA structures in less than four tandem repeats of G or C rich sequences. Here, using mechanical unfolding at the single-molecule level, electrophoretic mobility shift assay (EMSA), circular dichroism (CD), and ultraviolet (UV) spectroscopy, we report an intramolecularly folded non-B DNA structure in three tandem cytosine rich repeats, 5'-TGTC4ACAC4TGTC4ACA (ILPR-I3), in the human insulin linked polymorphic region (ILPR). The thermal denaturation analyses of the sequences with systematic C to T mutations have suggested that the structure is linchpinned by a stack of hemiprotonated cytosine pairs between two terminal C4 tracts. Mechanical unfolding and Br2 footprinting experiments on a mixture of the ILPR-I3 and a 5′-C4TGT fragment have further indicated that the structure serves as a building block for intermolecular i-motif formation. The existence of such a conformation under acidic or neutral pH complies with the strand-by-strand folding pathway of ILPR i-motif structures
QCD quantum correlation and multi-parton dynamics
Protons and neutrons are known to be the building blocks of matter, and also known to be the bound states of quarks and gluons - the partons, whose dynamics is best described by Quantum Chromodynamics (QCD). Perturbative QCD has been very successful in interpreting and predicting high-energy hadronic scattering processes by factorizing the leading contribution to the physical cross sections into a convolution of the perturbatively calculable short-distance part and the universal long-distance parton distribution functions (PDFs) of colliding hadrons. Besides testing QCD dynamics at the short-distance, these cross sections also probe partonic structure inside a colliding hadron via PDFs, which are often interpreted as the probability densities of finding a parton inside a hadron with a given longitudinal momentum fraction.
In this thesis I discuss the possibilities to explore the rich partonic dynamics inside a hadron or a large nucleus beyond the probability distributions. I will first explain why a difference of two transverse-spin dependent cross sections (or the measurement of the single transverse-spin asymmetry) can directly probe a set of new three-parton correlation functions. These correlation functions provide the first direct information on quantum correlation between quarks and gluons inside a polarized hadron. I will describe the basic formalism and the experimental measurements of these correlation functions. I will present the first derivation of evolution equations (or renormalization group equations) for these correlation functions. I will then discuss how to use the nuclear dependence of high energy nuclear collisions to extract the information on four-parton correlations inside a large nucleus or a nuclear medium. The measurements of the spin asymmetry and the anomalous nuclear dependence provide us new opportunities to explore the QCD dynamics and hadron structure beyond the parton probability distributions.</p
Detection of hydrological variations and their impacts on vegetation from multiple satellite observations in the Three-River Source Region of the Tibetan Plateau
The Three-River Source Region (TRSR) of the Tibetan Plateau (TP) is regarded as the “Chinese water tower”. Climate warming and the associated degradation of permafrost might change the water cycle and affect the alpine vegetation growth in the TRSR. However, the quantitative changes in the water budget and their impacts on the vegetation in the TRSR are poorly understood. In this study, the spatial-temporal changes in the hydrological variables and the normalized difference vegetation index (NDVI) during 2003–2014 were investigated using multiple satellite data and a remote sensing energy balance model. The results indicated that precipitation showed an increasing trend at a rate of 14.0 mm 10 a−1, and evapotranspiration (ET) showed a slight decreasing trend. The GRACE-derived total water storage (TWS) change presented a significant increasing trend at a rate of 35.1 mm a−1. The change in groundwater (GW) which showed an increasing trend at a rate of 18.5 mm a−1, was estimated by water budget. The time lag of the GRACE-TWS that was influenced by precipitation was more obviously than was the GLDAS-SM (Soil Moisture) change. The vegetation in the TRSR was greening during the study period, and the accumulation of the NDVI increased rapidly after 2008. The effect of total TWS and GLDAS-SM on vegetation was considerably more than that the effects of other factors in this region. It was concluded that the hydrological cycle had obviously changed and that more soil water was transferred into the GW since the aquiclude changed due to climate warming. The increasing area and number of lakes and the thickening of the active layer in the permafrost area led to the greater infiltration of surface water into the groundwater, which resulted in increased water storage
Tertiary DNA Structure in the Single-Stranded hTERT Promoter Fragment Unfolds and Refolds by Parallel Pathways via Cooperative or Sequential Events
The discovery of G-quadruplexes and other DNA secondary
elements
has increased the structural diversity of DNA well beyond the ubiquitous
double helix. However, it remains to be determined whether tertiary
interactions can take place in a DNA complex that contains more than
one secondary structure. Using a new data analysis strategy that exploits
the hysteresis region between the mechanical unfolding and refolding
traces obtained by a laser-tweezers instrument, we now provide the
first convincing kinetic and thermodynamic evidence that a higher
order interaction takes place between a hairpin and a G-quadruplex
in a single-stranded DNA fragment that is found in the promoter region
of human telomerase. During the hierarchical unfolding or refolding
of the DNA complex, a 15-nucleotide hairpin serves as a common species
among three intermediates. Moreover, either a mutant that prevents
this hairpin formation or the addition of a DNA fragment complementary
to the hairpin destroys the cooperative kinetic events by removing
the tertiary interaction mediated by the hairpin. The coexistence
of the sequential and the cooperative refolding events provides direct
evidence for a unifying kinetic partition mechanism previously observed
only in large proteins and complex RNA structures. Not only does this
result rationalize the current controversial observations for the
long-range interaction in complex single-stranded DNA structures,
but also this unexpected complexity in a promoter element provides
additional justification for the biological function of these structures
in cells