We present the first lattice result of the near threshold $ \Lambda_c\Lambda_c $ scattering with $ I(J^P) = 0(0^+) $ . The calculation is performed on two $ N_f = 2+1 $ Wilson-Clover ensembles with pion mass $ m_\pi \sim 303 $ MeV and lattice spacing $ a = 0.07746 $ fm. Lüscher's finite volume method is utilized to extract the scattering parameters from the finite-volume spectrum. The coupled channel $ \Xi_{cc}N $ is ignored in the scattering analysis based on the observation that the energy levels computed from the $ \Lambda_c\Lambda_c $ and $ \Xi_{cc}N $ operators do not mix. The $ \Sigma_c\Sigma_c $ channel is not included either since the energy range explored in this study is well below its threshold. Our results indicate that the interaction in the $ \Lambda_c\Lambda_c $ single channel is repulsive, and the scattering length is determined to be $ a_0 = -0.21(4)(8) $ fm, where the first error is statistical and the second is systematic.

China

Hanyang Xing

Yiqi Geng

Chuan Liu

Liuming Liu

Peng Sun

Jiajun Wu

Zhicheng Yan

Ruilin Zhu

Lattice QCD study of Λ $\textit{c}$ Λ $\textit{c}$ scattering * Supported by NSFC (12293060, 12293061, 12293063, 12175279, 12435002, 12322503, 12175239). L. Liu also acknowledges the Strategic Priority Research Program of the Chinese Academy of Sciences with (XDB34030301) and Guangdong Major Project of Basic and Applied Basic Research (2020B0301030008). We also acknowledge the Science and Education Integration Young Faculty Project of University of Chinese Academy of Sciences (YSBR-101)

<p>We report a study of the determination of the intrinsic transverse momentum of partons, the intrinsic <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><msub><mi>k</mi><mi>T</mi></msub></math>, from the dilepton transverse momentum <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><msub><mi>p</mi><mi>T</mi></msub></math> in Drell-Yan (DY) production at hadron colliders. The result shows that a good sensitivity to the intrinsic <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><msub><mi>k</mi><mi>T</mi></msub></math> distribution is achieved by measuring relative ratios between the cross sections of suitably defined low-<math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><msub><mi>p</mi><mi>T</mi></msub></math> and high-<math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><msub><mi>p</mi><mi>T</mi></msub></math> regions. The study is performed through both a pseudodata test and an extraction from measurements of the DY process by the CMS Collaboration. Since the methodology does not rely on any dedicated partition of bins, this <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><msub><mi>p</mi><mi>T</mi></msub></math>-ratio observable requires less special treatment in very low <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><msub><mi>p</mi><mi>T</mi></msub></math> regions and propagates lower systematic uncertainties induced from unfolding or momentum migration, in contrast with previous proposals of using a fine-binning measurement of the differential cross section.</p>

Wenxiao Zhan

Siqi Yang

Minghui Liu

United Kingdom

Belgium

Francesco Hautmann

Liang Han

Coarse-grained binning in Drell-Yan transverse momentum spectra

The measurements of the total cross section of the <ns0:math xmlns:ns0="http://www.w3.org/1998/Math/MathML" id="M2"><ns0:msup><ns0:mrow><ns0:mi>e</ns0:mi></ns0:mrow><ns0:mrow><ns0:mo>+</ns0:mo></ns0:mrow></ns0:msup><ns0:msup><ns0:mrow><ns0:mi>e</ns0:mi></ns0:mrow><ns0:mrow><ns0:mo>&#8722;</ns0:mo></ns0:mrow></ns0:msup><ns0:mo>&#10230;</ns0:mo><ns0:mi>&#947;</ns0:mi><ns0:mi>&#947;</ns0:mi><ns0:mfenced open="(" close=")"><ns0:mrow><ns0:mi>&#947;</ns0:mi></ns0:mrow></ns0:mfenced></ns0:math> reaction from the VENUS, TOPAS, OPAL, DELPHI, ALEPH, and L3 collaborations, collected between 1989 and 2003, are used to perform a <ns0:math xmlns:ns0="http://www.w3.org/1998/Math/MathML" id="M3"><ns0:msup><ns0:mrow><ns0:mi>&#967;</ns0:mi></ns0:mrow><ns0:mrow><ns0:mn>2</ns0:mn></ns0:mrow></ns0:msup></ns0:math> test to validate the current quantum electrodynamics (QED) theory and search for possible deviations with the direct contact term annihilation. By observing a deviation from the QED predictions on the total cross section of the <ns0:math xmlns:ns0="http://www.w3.org/1998/Math/MathML" id="M4"><ns0:msup><ns0:mrow><ns0:mi>e</ns0:mi></ns0:mrow><ns0:mrow><ns0:mo>+</ns0:mo></ns0:mrow></ns0:msup><ns0:msup><ns0:mrow><ns0:mi>e</ns0:mi></ns0:mrow><ns0:mrow><ns0:mo>&#8722;</ns0:mo></ns0:mrow></ns0:msup><ns0:mo>&#10230;</ns0:mo><ns0:mi>&#947;</ns0:mi><ns0:mi>&#947;</ns0:mi><ns0:mfenced open="(" close=")"><ns0:mrow><ns0:mi>&#947;</ns0:mi></ns0:mrow></ns0:mfenced></ns0:math> reaction above <ns0:math xmlns:ns0="http://www.w3.org/1998/Math/MathML" id="M5"><ns0:msqrt><ns0:mrow><ns0:mi>s</ns0:mi></ns0:mrow></ns0:msqrt><ns0:mo>=</ns0:mo><ns0:mn>180.0</ns0:mn></ns0:math>&#8201;GeV, a non-QED direct contact term is introduced following the dimension 6 effective theory to explain the deviation. In the non-QED direct contact term, a threshold energy scale <ns0:math xmlns:ns0="http://www.w3.org/1998/Math/MathML" id="M6"><ns0:mi>&#923;</ns0:mi></ns0:math> is included and explained to the finite interaction length in direct contact term and in consequence the size of the electron involved in the annihilation area. The experimental data of the total cross section is compared to the QED cross section by a <ns0:math xmlns:ns0="http://www.w3.org/1998/Math/MathML" id="M7"><ns0:msup><ns0:mrow><ns0:mi>&#967;</ns0:mi></ns0:mrow><ns0:mrow><ns0:mn>2</ns0:mn></ns0:mrow></ns0:msup></ns0:math> test, which gives a best fit of the <ns0:math xmlns:ns0="http://www.w3.org/1998/Math/MathML" id="M8"><ns0:mi>&#923;</ns0:mi></ns0:math> to be <ns0:math xmlns:ns0="http://www.w3.org/1998/Math/MathML" id="M9"><ns0:mn>1576</ns0:mn><ns0:mo>&#177;</ns0:mo><ns0:mn>202</ns0:mn></ns0:math>&#8201;GeV, corresponding to a finite interaction length of <ns0:math xmlns:ns0="http://www.w3.org/1998/Math/MathML" id="M10"><ns0:msub><ns0:mrow><ns0:mi>r</ns0:mi></ns0:mrow><ns0:mrow><ns0:mi>e</ns0:mi></ns0:mrow></ns0:msub><ns0:mo>=</ns0:mo><ns0:mfenced open="(" close=")"><ns0:mrow><ns0:mn>1.25</ns0:mn><ns0:mo>&#177;</ns0:mo><ns0:mn>0.16</ns0:mn></ns0:mrow></ns0:mfenced><ns0:mo>&#215;</ns0:mo><ns0:mn>1</ns0:mn><ns0:msup><ns0:mrow><ns0:mn>0</ns0:mn></ns0:mrow><ns0:mrow><ns0:mo>&#8722;</ns0:mo><ns0:mn>17</ns0:mn></ns0:mrow></ns0:msup></ns0:math> (cm). In the direct contact term annihilation, this interaction length is a measure of the size of an electron <ns0:math xmlns:ns0="http://www.w3.org/1998/Math/MathML" id="M11"><ns0:msub><ns0:mrow><ns0:mi>r</ns0:mi></ns0:mrow><ns0:mrow><ns0:mi>e</ns0:mi></ns0:mrow></ns0:msub></ns0:math>. By combining all the data results from the mentioned collaborations, we have at least 2 to 3 times more statistics than every single experiment at high <ns0:math xmlns:ns0="http://www.w3.org/1998/Math/MathML" id="M12"><ns0:msqrt><ns0:mrow><ns0:mi>s</ns0:mi></ns0:mrow></ns0:msqrt></ns0:math> region. This induces the best precision on <ns0:math xmlns:ns0="http://www.w3.org/1998/Math/MathML" id="M13"><ns0:msub><ns0:mrow><ns0:mi>r</ns0:mi></ns0:mrow><ns0:mrow><ns0:mi>e</ns0:mi></ns0:mrow></ns0:msub></ns0:math> compared to the previous measurements.

Yutao Chen

Switzerland

Jürgen Ulbricht

Hint for a Minimal Interaction Length in <ns0:math xmlns:ns0="http://www.w3.org/1998/Math/MathML" id="M1"><ns0:msup><ns0:mrow><ns0:mi>e</ns0:mi></ns0:mrow><ns0:mrow><ns0:mo>+</ns0:mo></ns0:mrow></ns0:msup><ns0:msup><ns0:mrow><ns0:mi>e</ns0:mi></ns0:mrow><ns0:mrow><ns0:mo>&#8722;</ns0:mo></ns0:mrow></ns0:msup><ns0:mo>&#10230;</ns0:mo><ns0:mi>&#947;</ns0:mi><ns0:mi>&#947;</ns0:mi></ns0:math> Annihilation in Total Cross Section of Center-of-Mass Energies 55-207&#8201;GeV

We present a study of the measurement of the effective weak mixing angle parameter (  $ {\sin^2\theta_{\text{eff}}^{{ \ell }}} $  ) at the Circular Electron Positron Collider (CEPC). As a fundamental physics parameter,   $ {\sin^2\theta_{\text{eff}}^{{ \ell }}} $   plays a key role not only in the global test of the standard model electroweak sector, but also in constraining the potential beyond standard model new physics at the high energy frontier. CEPC proposes a two year running period around the Z boson mass pole at high instataneous luminosity, providing a large data sample with   $ {\sin^2\theta_{\text{eff}}^{{ \ell }}} $   candidates generated in total. It allows a high precision measurement of   $ {\sin^2\theta_{\text{eff}}^{{ \ell }}} $   both in the lepton and quark final states, where the uncertainty can be one order of magnitude lower than any previous measurement at the LEP, SLC, Tevatron, and LHC. It will improve the overall precision of the   $ {\sin^2\theta_{\text{eff}}^{{ \ell }}} $   experimental determination to be comparable to the preicision of the theoretical calculation with two-loop radiative corrections, and it will also provide direct comparisons between different final states. In this paper, we also study the measurement of   $ {\sin^2\theta_{\text{eff}}^{{ \ell }}} $   in the high mass region. Taking data for one month, the precision of   $ {\sin^2\theta_{\text{eff}}^{{ \ell }}} $   measured at 130 GeV from b quark final state is 0.00010, which will be an important experimental observation on the energy-running effect of   $ {\sin^2\theta_{\text{eff}}^{{ \ell }}} $  .

Zhenyu Zhao

Manqi Ruan

Measurement of the effective weak mixing angle at the CEPC  

The forward-backward asymmetry (<math><msub><mi>A</mi><mrow><mi>F</mi><mi>B</mi></mrow></msub></math>) in the Drell-Yan process <math><mi>p</mi><mi>p</mi><mo>/</mo><mi>p</mi><mover><mi>p</mi><mo>¯</mo></mover><mo>→</mo><mi>Z</mi><msup><mi>γ</mi><mo>*</mo></msup><mo>→</mo><msup><mo>ℓ</mo><mo>+</mo></msup><msup><mo>ℓ</mo><mo>−</mo></msup></math> is sensitive to the proton structure information. Such information has been factorized into well-defined proton structure parameters which can be regarded as experimental observables. In this paper, we extract the structure parameters from the <math><msub><mi>A</mi><mrow><mi>F</mi><mi>B</mi></mrow></msub></math> distributions reported by the CMS Collaboration in <math><mi>p</mi><mi>p</mi></math> collisions at <math><msqrt><mi>s</mi></msqrt><mo>=</mo><mn>8</mn><mtext> </mtext><mtext> </mtext><mi>TeV</mi></math>, and by the D0 Collaboration in <math><mi>p</mi><mover><mi>p</mi><mo>¯</mo></mover></math> collisions at <math><msqrt><mi>s</mi></msqrt><mo>=</mo><mn>1.96</mn><mtext> </mtext><mtext> </mtext><mi>TeV</mi></math>. It is the first time that the unique parton information in the <math><msub><mi>A</mi><mrow><mi>F</mi><mi>B</mi></mrow></msub></math> spectrum can be decoupled from the electroweak calculation and measured as standalone observables, which can be used as new data constraints in the global quantum chromodynamics analysis of the parton distribution functions. Although the parton information in the <math><mi>p</mi><mi>p</mi></math> and <math><mi>p</mi><mover><mi>p</mi><mo>¯</mo></mover></math> collisions are different, and the precisions are statistically limited, the results from both the hadron colliders indicate that the down quark contribution might be higher in the data than their theoretical predictions.

Mingzhe Xie

Yao Fu

Tie-Jiun Hou

Sayipjamal Dulat

United States

C.P. Yuan

Measurement of the proton structure parameters in the forward-backward charge asymmetry

We propose the boost asymmetry of the diboson productions <math><msub><mi>q</mi><mi>i</mi></msub><msub><mover><mi>q</mi><mo>¯</mo></mover><mi>j</mi></msub><mo>→</mo><mi>V</mi><msup><mi>V</mi><mo>′</mo></msup></math> in <math><mi>p</mi><mi>p</mi></math> collisions (<math><mi>V</mi><msup><mi>V</mi><mo>′</mo></msup><mo>=</mo><mi>W</mi><mi>γ</mi></math>, <math><msup><mi>W</mi><mo>+</mo></msup><msup><mi>W</mi><mo>−</mo></msup></math>, and <math><mi>W</mi><mi>Z</mi></math>) as a new experimental observable, which can provide unique information on the proton structure. The boost asymmetry rises as the difference in the kinematics of the two bosons, that are coupled to the two different quark and antiquark initial states, respectively, and thus reflects different features of the <math><msub><mi>q</mi><mi>i</mi></msub></math> and <math><msub><mover><mi>q</mi><mo>¯</mo></mover><mi>j</mi></msub></math> parton densities. By comparing the kinematics of the two bosons, such as the boson energy or rapidity, the diboson events with <math><msub><mover><mi>q</mi><mo>¯</mo></mover><mi>j</mi></msub></math> having higher energy than <math><msub><mi>q</mi><mi>i</mi></msub></math> can be distinguished from those with <math><msub><mi>q</mi><mi>i</mi></msub></math> having higher energy than <math><msub><mover><mi>q</mi><mo>¯</mo></mover><mi>j</mi></msub></math>. This would provide unique information in some special parton momentum fraction regions, which cannot be directly proved by current <math><mi>W</mi></math> and <math><mi>Z</mi></math> measurements at the Large Hadron Collider or other deep inelastic scattering experiments.

Zihan Zhao

Boost asymmetry of the diboson productions in <math><mi>p</mi><mi>p</mi></math> collisions

The forward-backward charge asymmetry (<math><msub><mi>A</mi><mrow><mi>FB</mi></mrow></msub></math>) at hadron colliders is sensitive to both the electroweak (EW) symmetry breaking represented by the effective weak mixing angle <math><msup><mi>sin</mi><mn>2</mn></msup><msubsup><mi>θ</mi><mi>eff</mi><mrow><mo>ℓ</mo></mrow></msubsup></math>, and the proton structure information in the initial state modeled by the parton distribution functions (PDFs). Due to their strong correlation, the precisions of determination on <math><msup><mi>sin</mi><mn>2</mn></msup><msubsup><mi>θ</mi><mi>eff</mi><mrow><mo>ℓ</mo></mrow></msubsup></math> and PDFs using the measured <math><msub><mi>A</mi><mrow><mi>FB</mi></mrow></msub></math> spectrum are limited. In this paper, we define a set of structure parameters which factorize the unique proton information of the relative difference between quarks and antiquarks in the <math><msub><mi>A</mi><mrow><mi>FB</mi></mrow></msub></math> observation. Other than the conventional way of extracting <math><msup><mi>sin</mi><mn>2</mn></msup><msubsup><mi>θ</mi><mi>eff</mi><mrow><mo>ℓ</mo></mrow></msubsup></math> from the convolution of PDF and EW calculations, we propose a new method to simultaneously determine the value of <math><msup><mi>sin</mi><mn>2</mn></msup><msubsup><mi>θ</mi><mi>eff</mi><mrow><mo>ℓ</mo></mrow></msubsup></math> and the proton structure terms by fitting to the observed <math><msub><mi>A</mi><mrow><mi>FB</mi></mrow></msub></math> distribution, and point out the necessity of specifying additional observations to further reduce the uncertainties on the proton structure terms, respectively, so that model-independent high precision <math><msup><mi>sin</mi><mn>2</mn></msup><msubsup><mi>θ</mi><mi>eff</mi><mrow><mo>ℓ</mo></mrow></msubsup></math> and proton structure measurements can be achieved at the future LHC experiments.

Factorization of the forward-backward asymmetry and measurements of the weak mixing angle and proton structure at hadron colliders

We propose a new observable for the measurement of the forward–backward asymmetry  $$(A_{FB})$$  <math> <mrow> <mo>(</mo> <msub> <mi>A</mi> <mrow> <mi>FB</mi> </mrow> </msub> <mo>)</mo> </mrow> </math>   in Drell–Yan lepton production. At hadron colliders, the  $$A_{FB}$$  <math> <msub> <mi>A</mi> <mrow> <mi>FB</mi> </mrow> </msub> </math>   distribution is sensitive to both the electroweak (EW) fundamental parameter  $$\sin ^{2} \theta _{W}$$  <math> <mrow> <msup> <mo>sin</mo> <mn>2</mn> </msup> <msub> <mi>θ</mi> <mi>W</mi> </msub> </mrow> </math>  , the weak mixing angle, and the parton distribution functions (PDFs). Hence, the determination of  $$\sin ^{2} \theta _{W}$$  <math> <mrow> <msup> <mo>sin</mo> <mn>2</mn> </msup> <msub> <mi>θ</mi> <mi>W</mi> </msub> </mrow> </math>   and the updating of PDFs by directly using the same  $$A_{FB}$$  <math> <msub> <mi>A</mi> <mrow> <mi>FB</mi> </mrow> </msub> </math>   spectrum are strongly correlated. This correlation would introduce large bias or uncertainty into both precise measurements of EW and PDF sectors. In this article, we show that the sensitivity of  $$A_{FB}$$  <math> <msub> <mi>A</mi> <mrow> <mi>FB</mi> </mrow> </msub> </math>   on  $$\sin ^{2} \theta _{W}$$  <math> <mrow> <msup> <mo>sin</mo> <mn>2</mn> </msup> <msub> <mi>θ</mi> <mi>W</mi> </msub> </mrow> </math>   is dominated by its average value around the Z pole region, while the shape (or gradient) of the  $$A_{FB}$$  <math> <msub> <mi>A</mi> <mrow> <mi>FB</mi> </mrow> </msub> </math>   spectrum is insensitive to  $$\sin ^{2} \theta _{W}$$  <math> <mrow> <msup> <mo>sin</mo> <mn>2</mn> </msup> <msub> <mi>θ</mi> <mi>W</mi> </msub> </mrow> </math>   and contains important information on the PDF modeling. Accordingly, a new observable related to the gradient of the spectrum is introduced, and demonstrated to be able to significantly reduce the potential bias on the determination of  $$\sin ^{2} \theta _{W}$$  <math> <mrow> <msup> <mo>sin</mo> <mn>2</mn> </msup> <msub> <mi>θ</mi> <mi>W</mi> </msub> </mrow> </math>   when updating the PDFs using the same  $$A_{FB}$$  <math> <msub> <mi>A</mi> <mrow> <mi>FB</mi> </mrow> </msub> </math>   data.

Renyou Zhang

Chen Wang

Hang Yin

Reduction of the electroweak correlation in the PDF updating by using the forward–backward asymmetry of Drell–Yan process

We investigate the parton distribution function (PDF) uncertainty in the measurement of the effective weak mixing angle   $\sin^2 \theta _{{\rm{eff}}}^{\ell}$   at the CERN Large Hadron Collider (LHC). The PDF-induced uncertainty is large in proton-proton collisions at the LHC due to the dilution effect. The measurement of the Drell-Yan forward-backward asymmetry (   $\sin^2 \theta _{{\rm{eff}}}^{\ell}$  ) at the LHC can be used to reduce the PDF uncertainty in the   $\sin^2 \theta _{{\rm{eff}}}^{\ell}$   measurement. However, when including the full mass range of lepton pairs in the   $\sin^2 \theta _{{\rm{eff}}}^{\ell}$   data analysis, the correlation between the PDF updating procedure and the   $\sin^2 \theta _{{\rm{eff}}}^{\ell}$   extraction leads to a sizable bias in the obtained   $\sin^2 \theta _{{\rm{eff}}}^{\ell}$   value. From our studies, we find that the bias can be significantly reduced by removing Drell-Yan events with invariant mass around the Z-pole region, while most of the sensitivity in reducing the PDF uncertainty remains. Furthermore, the lepton charge asymmetry in the W boson events as a function of the rapidity of the charged leptons,   $\sin^2 \theta _{{\rm{eff}}}^{\ell}$  , is known to be another observable which can be used to reduce the PDF uncertainty in the   $\sin^2 \theta _{{\rm{eff}}}^{\ell}$   measurement. The constraint from   $\sin^2 \theta _{{\rm{eff}}}^{\ell}$   is complementary to that from   $\sin^2 \theta _{{\rm{eff}}}^{\ell}$  , and thus no bias affects the   $\sin^2 \theta _{{\rm{eff}}}^{\ell}$   extraction. The studies are performed using the error PDF Updating Method Package (ePump), which is based on Hessian updating methods. In this article, the CT14HERA2 PDF set is used as an example.

Carl Schmidt

C.-P. Yuan

Reduction of PDF uncertainty in the measurement of the weak mixing angle at the ATLAS experiment  

This exploratory study computes two-photon decay widths of pseudo-scalar (
					) and scalar (
					) charmonium using two ensembles of 
					 twisted mass lattice QCD gauge configurations. The simulation is performed using two lattice ensembles with lattice spacings 
					 fm with size 
					 and 
					 fm with size 
					. The decay widths for the two charmonia are obtained within the expected ballpark, but are however smaller than the experimental ones. Possible reasons for these discrepancies are discussed.
				

Ying Chen

Ming Gong

Ning Li

Yu-Bin Liu

Zhaofeng Liu

Jian-Ping Ma

Yu Meng

Chao Xiong

Ke-Long Zhang

Lattice study of two-photon decay widths for scalar and pseudo-scalar charmonium This work is supported in part by the National Science Foundation of China (NSFC) (11335001, 11275169, 11405178, 11935017, 11575196, 11875169, 11775229). It is also supported in part by the DFG and the NSFC (11261130311) through funds provided to the Sino-Germen CRC 110 symmetries and the Emergence of Structure in QCD. This work is also funded in part by National Basic Research Program of China (973 Program) (2015CB856700). M. Gong and Z. Liu are partially supported by the Youth Innovation Promotion Association of CAS (2013013). This work is also supported by the Scientific Research Program Funded by Shaanxi Provincial Education Department (19JK0391) andNatural Science Basic Research Plan in Shaanxi Province of China (2019JM-001)