In this work, real photon production scattering kernels from jet-medium interactions in the QCD medium are perturbatively calculated using the higher-twist (HT) formalism. Focus is given towards real photon production from a highly virtual (and highly energetic) quark, taking into account heavy-quark mass scales [<a href="http://dx.doi.org/10.1103/PhysRevC.94.054902">Phys. Rev. C 94, 054902 (2016)</a>], fermion-boson conversion processes [<a href="http://dx.doi.org/10.1016/j.nuclphysa.2007.06.009">Nucl. Phys. A 793, 128 (2007)</a>], as well as coherence effects [<a href="http://dx.doi.org/10.1103/PhysRevC.105.024908">Phys. Rev. C 105, 024908 (2022)</a>]. A generalized factorization procedure, such as that used in <math xmlns="http://www.w3.org/1998/Math/MathML"><mrow><mi>e</mi><mtext>−</mtext><mi>A</mi></mrow></math> deep-inelastic scattering, is employed to derive an improved single-scattering medium-induced photon emission kernels that go beyond the traditional in-medium gluon exchange approximation. Diagrams with real-photon emission from the hard quark are classified based on the final-state particles, and include two types of scattering kernels at <math xmlns="http://www.w3.org/1998/Math/MathML"><mrow><mi>O</mi><mo>(</mo><msub><mi>α</mi><mi>em</mi></msub><msub><mi>α</mi><mi>s</mi></msub><mo>)</mo></mrow></math> giving the following final states: (i) real photon and real quark, (ii) real photon and real gluon. The collisional kernels, thus derived, include full phase factors from all nonvanishing diagrams and complete second-order derivative terms in the transverse momentum gradient expansion. Moreover, the calculation includes heavy-quark mass effects, thus exploring heavy-quark energy loss. The in-medium parton distribution functions and the related jet transport coefficients have a hard transverse momentum dependence (of the emitted gluon or photon) present within the phase factor. It is observed that the jet transport coefficients resemble the transverse-momentum-dependent parton distribution functions.

Canada

Amit Kumar

Gojko Vujanovic

Bremsstrahlung photon contributions to parton energy loss at high virtuality <math xmlns="http://www.w3.org/1998/Math/MathML"><msup><mi>Q</mi><mn>2</mn></msup></math>: A perturbative calculation at <math xmlns="http://www.w3.org/1998/Math/MathML"><mrow><mi>O</mi><mo>(</mo><msub><mi>α</mi><mi>s</mi></msub><msub><mi>α</mi><mtext>em</mtext></msub><mo>)</mo></mrow></math>

We measure the spin-density matrix elements (SDMEs) for the photoproduction of <math xmlns="http://www.w3.org/1998/Math/MathML"><mrow><mi>ϕ</mi><mo>(</mo><mn>1020</mn><mo>)</mo></mrow></math> off of the proton in its decay to <math xmlns="http://www.w3.org/1998/Math/MathML"><mrow><msubsup><mi>K</mi><mi>S</mi><mn>0</mn></msubsup><msubsup><mi>K</mi><mi>L</mi><mn>0</mn></msubsup></mrow></math>, using 105 <math xmlns="http://www.w3.org/1998/Math/MathML"><msup><mrow><mi>pb</mi></mrow><mrow><mo>−</mo><mn>1</mn></mrow></msup></math> of data collected with a linearly polarized photon beam using the GlueX experiment. The SDMEs are measured in nine bins of the squared four-momentum transfer <math xmlns="http://www.w3.org/1998/Math/MathML"><mi>t</mi></math> in the range <math xmlns="http://www.w3.org/1998/Math/MathML"><mrow><mo>−</mo><mi>t</mi><mo>=</mo><mn>0.15</mn><mo>−</mo><mn>1.0</mn></mrow></math> <math xmlns="http://www.w3.org/1998/Math/MathML"><msup><mrow><mi>GeV</mi></mrow><mn>2</mn></msup></math>, providing the first measurement of their <math xmlns="http://www.w3.org/1998/Math/MathML"><mi>t</mi></math> dependence for photon beam energies of <math xmlns="http://www.w3.org/1998/Math/MathML"><mrow><msub><mi>E</mi><mi>γ</mi></msub><mo>=</mo><mn>8.2</mn><mo>−</mo><mn>8.8</mn></mrow></math> GeV. We confirm the dominance of Pomeron exchange in this region and put constraints on the contribution of other Regge exchanges. We also find that helicity amplitudes where the helicity of the photon and <math xmlns="http://www.w3.org/1998/Math/MathML"><mrow><mi>ϕ</mi><mo>(</mo><mn>1020</mn><mo>)</mo></mrow></math> differ by two units are negligible.

Germany

F. Afzal

United States

C.S. Akondi

M. Albrecht

M. Amaryan

S. Arrigo

V. Arroyave

A. Asaturyan

A. Austregesilo

Z. Baldwin

F. Barbosa

J. Barlow

E. Barriga

R. Barsotti

D. Barton

V. Baturin

V.V. Berdnikov

T. Black

W. Boeglin

M. Boer

W.J. Briscoe

T. Britton

R. Brunner

S. Cao

E. Chudakov

G. Chung

P.L. Cole

O. Cortes

V. Crede

M.M. Dalton

United Kingdom

D. Darulis

A. Deur

S. Dobbs

Russia

A. Dolgolenko

M. Dugger

R. Dzhygadlo

D. Ebersole

M. Edo

H. Egiyan

T. Erbora

P. Eugenio

A. Fabrizi

C. Fanelli

China

S. Fang

A.M. Foda

M. Fritsch

S. Furletov

L. Gan

H. Gao

A. Gardner

A. Gasparian

D.I. Glazier

C. Gleason

V.S. Goryachev

B. Grube

J. Guo

L. Guo

J. Hernandez

K. Hernandez

N.D. Hoffman

D. Hornidge

Chile

G. Huber

P. Hurck

W. Imoehl

D.G. Ireland

M.M. Ito

I. Jaegle

N.S. Jarvis

T. Jeske

M. Jing

R.T. Jones

Armenia

V. Kakoyan

G. Kalicy

V. Khachatryan

Greece

C. Kourkoumelis

A. LaDuke

I. Larin

D. Lawrence

D.I. Lersch

H. Li

B. Liu

K. Livingston

L. Lorenti

V. Lyubovitskij

A. Mahmood

H. Marukyan

V. Matveev

M. McCaughan

M. McCracken

C.A. Meyer

R. Miskimen

R.E. Mitchell

K. Mizutani

P. Moran

V. Neelamana

L. Ng

E. Nissen

S. Orešić

A.I. Ostrovidov

Z. Papandreou

C. Paudel

Measurement of spin-density matrix elements in <math xmlns="http://www.w3.org/1998/Math/MathML"><mrow><mi>ϕ</mi><mrow><mo>(</mo><mn>1020</mn><mo>)</mo></mrow><mo>→</mo><msubsup><mi>K</mi><mi>S</mi><mn>0</mn></msubsup><msubsup><mi>K</mi><mi>L</mi><mn>0</mn></msubsup></mrow></math> photoproduction with a linearly polarized photon beam at <math xmlns="http://www.w3.org/1998/Math/MathML"><mrow><msub><mi>E</mi><mi>γ</mi></msub><mo>=</mo><mn>8.2</mn><mo>–</mo><mn>8.8</mn><mo> </mo><mi>GeV</mi></mrow></math>

Inclusive electron scattering cross sections off a hydrogen target at a beam energy of 10.6 GeV have been measured with data collected from the CLAS12 spectrometer at Jefferson Laboratory. These first absolute cross sections from CLAS12 cover a wide kinematic area in invariant mass <math xmlns="http://www.w3.org/1998/Math/MathML"><mi>W</mi></math> of the final state hadrons from the pion threshold up to 2.5 GeV for each bin in virtual photon four-momentum transfer squared <math xmlns="http://www.w3.org/1998/Math/MathML"><msup><mi>Q</mi><mn>2</mn></msup></math> from 2.55 to <math xmlns="http://www.w3.org/1998/Math/MathML"><mrow><mn>10.4</mn><mspace width="0.16em"></mspace><msup><mrow><mi>GeV</mi></mrow><mn>2</mn></msup></mrow></math> owing to the large scattering angle acceptance of the CLAS12 detector. Comparison of the cross sections with the resonant contributions computed from the CLAS results on the nucleon resonance electroexcitation amplitudes has demonstrated a promising opportunity to extend the information on their <math xmlns="http://www.w3.org/1998/Math/MathML"><msup><mi>Q</mi><mn>2</mn></msup></math> evolution up to 10 <math xmlns="http://www.w3.org/1998/Math/MathML"><msup><mrow><mi>GeV</mi></mrow><mn>2</mn></msup></math>. Together these results from CLAS and CLAS12 offer good prospects for probing the nucleon parton distributions at large fractional parton momenta <math xmlns="http://www.w3.org/1998/Math/MathML"><mi>x</mi></math> for <math xmlns="http://www.w3.org/1998/Math/MathML"><mrow><mi>W</mi><mo>&lt;</mo><mn>2.5</mn></mrow></math> GeV, while covering the range of distances where the transition from the strongly coupled to the perturbative regimes is expected.

V. Klimenko

D.S. Carman

R.W. Gothe

K. Joo

N. Markov

V.I. Mokeev

G. Niculescu

P. Achenbach

France

J.S. Alvarado

W. Armstrong

H. Atac

H. Avakian

Saudi Arabia

L. Baashen

N.A. Baltzell

Italy

L. Barion

M. Bashkanov

M. Battaglieri

F. Benmokhtar

A. Bianconi

A.S. Biselli

S. Boiarinov

F. Bossù

K.-Th. Brinkmann

W.K. Brooks

V.D. Burkert

S. Bueltmann

R. Capobianco

J. Carvajal

A. Celentano

P. Chatagnon

G. Ciullo

A. D'Angelo

N. Dashyan

M. Defurne

R. De Vita

S. Diehl

C. Dilks

C. Djalali

R. Dupré

A. El Alaoui

L. El Fassi

L. Elouadrhiri

S. Fegan

I.P. Fernando

A. Filippi

G. Gavalian

G.P. Gilfoyle

K. Hafidi

H. Hakobyan

M. Hattawy

F. Hauenstein

T.B. Hayward

D. Heddle

A.N. Hiller Blin

A. Hobart

M. Holtrop

Y. Ilieva

E.L. Isupov

H. Jiang

South Korea

H.S. Jo

S. Joosten

T. Kageya

D. Keller

A. Kim

W. Kim

H.T. Klest

A. Kripko

V. Kubarovsky

S.E. Kuhn

L. Lanza

S. Lee

P. Lenisa

I.J.D. MacGregor

D. Marchand

D. Martiryan

V. Mascagna

D. Matamoris

B. McKinnon

T. Mineeva

M. Mirazita

C. Munoz Camacho

Inclusive electron scattering in the resonance region off a hydrogen target with CLAS12