nuclear gluons with charm at eic* · 2016. 2. 17. · open charm production charles hyde old...

Nuclear Gluons with Charm at EIC*

*Probing High-x Gluons in Nuclei via

Open Charm Production

Charles Hyde Old Dominion University

Next Generation Nuclear Physics with JLab12 and EIC 10–13 February 2016

Florida International University

Gluons at Large-x in (e,e’)? Gluons are a low-x phenomenon   ∼50% of gluon momentum sum rule is at x > 0.1

  g(x) ≈ d(x) quarks at x ≥ 0.3 (within errors)

C.Hyde, Next Gen. Nucl. Phys. 10–13 Feb 2016

EMC Effect’: Anti-Shadowing

  Anti-shadowing is not anti-quarks! FermiLab Drell-Yan E722

L. Frankfurt et al. / Physics Reports 512 (2012) 255–393 305

Fig. 34. Prediction for nuclear PDFs and structure functions for 208Pb. The ratios Rj (u and c quarks and gluons) and RF2 as functions of Bjorken x at Q 2 = 4,10, 100 and 10, 000 GeV2. The four upper panels correspond to FGS10_H; the four lower panels correspond to FGS10_L.

The numerical value of the exponent � = 0.25 in Eq. (126) can be understood as follows. The x dependence of nuclearshadowing at small x is primarily driven by the xP dependence of the Pomeron flux fP/p(xP) / 1/x(2↵P�1)

P / 1/x1.22P . There-fore, in the very small x limit, one expects from Eq. (64) that, approximately,

�F2A(x,Q 2)/A /✓1x

◆0.22

,

�xgA(x,Q 2)/A /✓1x

◆0.22

, (127)

which is consistent with our numerical result in Eq. (126).When we present our predictions for nuclear shadowing in the form of the ratios of the nuclear to nucleon PDFs, it is

somewhat difficult to see the leading twist nature of the predicted nuclear shadowing because of the rapid Q 2 dependenceof the free nucleon structure functions and PDFs. In order to see the leading twist nuclear shadowing more explicitly, oneshould examine the absolute values of the shadowing corrections.

Fig. 38 presents |�F2A(x,Q 2)/A| and |�xgA(x,Q 2)/A| as functions of Q 2 at fixed x = 10�4 (first and third rows) andx = 10�3 (second and fourth rows) for 40Ca (four upper panels) and 208Pb (four lower panels). The solid curves correspondto FGS10_H; the dotted curves correspond to FGS10_L. Also, for comparison, presented by the dot-dashed curves, we give

0.7

0.8

0.9

1

1.1

0.01 0.1 1

DY(E772)DIS(NMC)

R(Ca/2 H)

x

  Anti-shadowing is glue


Gluons and Charm @ JLab 12 GeV

  First CLAS12 experiment, circa FY17+   e + p à e’ + X, Ee = 11 GeV   e + p à e’ + p + (J/Ψ à e+e–)

  Gluon GPD at xg = (MJ/Ψ )2/(W2–M2) > 0.5 for Q2≥ 1 GeV2 LHCb resonance in p ✕ J/Ψ channel: PRL 115, 072001 (2015)   CLAS12 forward tagger W ≤ 4.5 GeV for Q2<<1 GeV2

  Time-like Compton scattering (TCS) up to M( J/Ψ) approved for CLAS12, SoLID (Hall A)

  TCS discussions for Halls C & D

higher mass states are 9 and 12 standard deviations,respectively.Analysis and results.—We use data corresponding to

1 fb−1 of integrated luminosity acquired by the LHCbexperiment in pp collisions at 7 TeV center-of-massenergy, and 2 fb−1 at 8 TeV. The LHCb detector [13]is a single-arm forward spectrometer covering thepseudorapidity range, 2 < η < 5. The detector includes ahigh-precision tracking system consisting of a silicon-stripvertex detector surrounding the pp interaction region [14],a large-area silicon-strip detector located upstream of adipole magnet with a bending power of about 4 Tm, andthree stations of silicon-strip detectors and straw drift tubes[15] placed downstream of the magnet. Different types ofcharged hadrons are distinguished using information fromtwo ring-imaging Cherenkov detectors [16]. Muons areidentified by a system composed of alternating layers ofiron and multiwire proportional chambers [17].

Events are triggered by a J=ψ → μþμ− decay, requiringtwo identified muons with opposite charge, each withtransverse momentum, pT , greater than 500 MeV. Thedimuon system is required to form a vertex with a fitχ2 < 16, to be significantly displaced from the nearest ppinteraction vertex, and to have an invariant mass within120 MeV of the J=ψ mass [12]. After applying theserequirements, there is a large J=ψ signal over a smallbackground [18]. Only candidates with dimuon invariantmass between −48 and þ43 MeV relative to the observedJ=ψ mass peak are selected, the asymmetry accounting forfinal-state electromagnetic radiation.Analysis preselection requirements are imposed prior to

using a gradient boosted decision tree, BDTG [19], thatseparates the Λ0

b signal from backgrounds. Each track isrequired to be of good quality and multiple reconstructionsof the same track are removed. Requirements on theindividual particles include pT > 550 MeV for muons,

[GeV]pKm1.4 1.6 1.8 2.0 2.2 2.4

Eve

nts/

(20

MeV

)

500

1000

1500

2000

2500

3000

LHCb(a)

data

phase space

[GeV]pψ/Jm4.0 4.2 4.4 4.6 4.8 5.0

Eve

nts/

(15

MeV

)

200

400

600

800 LHCb(b)

FIG. 2 (color online). Invariant mass of (a) K−p and (b) J=ψp combinations from Λ0b → J=ψK−p decays. The solid (red) curve is the

expectation from phase space. The background has been subtracted.

[GeV]pKm1.4 1.6 1.8 2 2.2 2.4 2.6

Eve

nts/

(15

MeV

)

0

200

400

600

800

1000

1200

1400

1600

1800

2000

2200

LHCb

datatotal fitbackground

(4450)cP(4380)cP(1405)Λ(1520)Λ(1600)Λ(1670)Λ(1690)Λ(1800)Λ(1810)Λ(1820)Λ(1830)Λ(1890)Λ(2100)Λ(2110)Λ

[GeV]pψ/Jm4 4.2 4.4 4.6 4.8 5

Eve

nts/

(15

MeV

)

0

100

200

300

400

500

600

700

800

LHCb(a) (b)

FIG. 3 (color online). Fit projections for (a)mKp and (b)mJ=ψp for the reduced Λ" model with two Pþc states (see Table I). The data are

shown as solid (black) squares, while the solid (red) points show the results of the fit. The solid (red) histogram shows the backgrounddistribution. The (blue) open squares with the shaded histogram represent the Pcð4450Þþ state, and the shaded histogram topped with(purple) filled squares represents the Pcð4380Þþ state. Each Λ" component is also shown. The error bars on the points showing the fitresults are due to simulation statistics.

PRL 115, 072001 (2015) P HY S I CA L R EV I EW LE T T ER S week ending14 AUGUST 2015

072001-2

Pc(4450) Pc(4380)

CLAS12

LHCb 2015


Nuclear gluons with charm at EIC JLab FY16 LDRD Project LD1601

  E. Chudakov, D. Higinbotham, C. H., S. Furletov, Yu. Furletova, D. Nguyen, M. Stratmann, M. Strikman, C. Weiss.

https://wiki.jlab.org/nuclear_gluons/index.php/Main_Page

  Investigate feasibility of direct measurements (with EIC@JLab) of nuclear gluons at xglue ≥ 0.1, via open-charm (open-beauty) production.

  Simulation codes under development   Analytic codes,   MC + fragmentation via HVQDIS, PYTHIA...

  Detector Simulations in GEMC/GEANT4

  Initial results


Gluons & Nuclear Binding

  Shadowing (coherent gluons from NN, NNN ...)   ALICE data:

ultra-peripheral AAà AA J/Ψ

  x = 0.001 — 0.01

  Expectation of gluonic anti-shadowing at x ≈ 0.1

L. Frankfurt et al. / Physics Reports 512 (2012) 255–393 305

Fig. 34. Prediction for nuclear PDFs and structure functions for 208Pb. The ratios Rj (u and c quarks and gluons) and RF2 as functions of Bjorken x at Q 2 = 4,10, 100 and 10, 000 GeV2. The four upper panels correspond to FGS10_H; the four lower panels correspond to FGS10_L.

The numerical value of the exponent � = 0.25 in Eq. (126) can be understood as follows. The x dependence of nuclearshadowing at small x is primarily driven by the xP dependence of the Pomeron flux fP/p(xP) / 1/x(2↵P�1)

P / 1/x1.22P . There-fore, in the very small x limit, one expects from Eq. (64) that, approximately,

�F2A(x,Q 2)/A /✓1x

◆0.22

,

�xgA(x,Q 2)/A /✓1x

◆0.22

, (127)

which is consistent with our numerical result in Eq. (126).When we present our predictions for nuclear shadowing in the form of the ratios of the nuclear to nucleon PDFs, it is

somewhat difficult to see the leading twist nature of the predicted nuclear shadowing because of the rapid Q 2 dependenceof the free nucleon structure functions and PDFs. In order to see the leading twist nuclear shadowing more explicitly, oneshould examine the absolute values of the shadowing corrections.

Fig. 38 presents |�F2A(x,Q 2)/A| and |�xgA(x,Q 2)/A| as functions of Q 2 at fixed x = 10�4 (first and third rows) andx = 10�3 (second and fourth rows) for 40Ca (four upper panels) and 208Pb (four lower panels). The solid curves correspondto FGS10_H; the dotted curves correspond to FGS10_L. Also, for comparison, presented by the dot-dashed curves, we give

0.0001 0.001 0.01 xglue

)2 =

2.4

GeV

2 µ(x

, PbR

0.10.20.30.40.50.60.70.80.9

HKN07LOnDSLOEPS08 LOEPS09 LOEPS09 uncertainty


Tagging Photon-Gluon Fusion via Open Charm Production

xglueG(xglue) support localized near xglue ≥ xBj[1+4mh

2/Q2] .

Results: Sensitivity to large–x′ gluons 8

_

e’

h

h

x, Q2

G ( )x’A

x’

e

= c, b

Fh2 (x,Q

2) =

∫ 1

ax

dx′

x′x′G(x′) F h

g (x/x′, Q2, m2

h, µ2)

coefficient function

a = 1 +4m2

h

Q2sets limit of x′ integral

0

2

4

6

8

0 0.2 0.4 0.6 0.8 1

Inte

gran

d o

f F 2

(cha

rm)

[nor

mal

ized

]

x’

x = 0.1, Q2 = 10 GeV2

x = 0.2, Q2 = 10 GeV2

• Integrand localized in x′ aroundlower limit ax

• Heavy quark production probeslarge–x′ gluons “almost locally”


_

e’

h

h

x, Q2

G ( )x’A

x’

e

= c, b

Fh2 (x,Q

2) =

∫ 1

ax

dx′

x′x′G(x′) F h

g (x/x′, Q2, m2

h, µ2)


a = 1 +4m2

h


0

2

4

6

8

0 0.2 0.4 0.6 0.8 1

Inte

gran

d o

f F 2

(cha

rm)

[nor

mal

ized

]

x’

x = 0.1, Q2 = 10 GeV2

x = 0.2, Q2 = 10 GeV2




_

e’

h

h

x, Q2

G ( )x’A

x’

e

= c, b

Fh2 (x,Q

2) =

∫ 1

ax

dx′

x′x′G(x′) F h

g (x/x′, Q2, m2

h, µ2)


a = 1 +4m2

h


0

2

4

6

8

0 0.2 0.4 0.6 0.8 1

Inte

gran

d o

f F 2

(cha

rm)

[nor

mal

ized

]

x’

x = 0.1, Q2 = 10 GeV2

x = 0.2, Q2 = 10 GeV2




Total Open-Charm Rates @ EIC

  Tagging efficiency study in-process

  Expected ≥ 10%

Results: Total charm rate at EIC 7

102

103

104

105

106

107

108

109

1010

0.001 0.01 0.1 1

Num

ber o

f eve

nts

x

seN = 1000 GeV2, L(int) = 107 nb-1

total

charm

Proton 5 < Q2 < 15 GeV2

5 < Q2 < 50 GeV2

• Here 5 bins per decade in x, single wide bin in Q2

• Rates drop rapidly at large x• Nuclear rates comparable: Structure function Fc

2A ∼ AFc2N , but luminosity LA ≈ LN/A


Open Charm Reconstruction

  cà D0 à π+ K–

  c à D*+ à π+slow

+D0 à π+ K–

21 Oct. 2015 Sergey Furletov 5

Charm production in DIS

BGF process provides direct sensitivity to thegluon density in the proton.

Due to the large gluon density in the proton, theBGF processes gives large contributions to DIS

The leading order diagram

The measurement was performed in the kinematic range of 1.5 < Q2 < 1000 GeV 2

and 0.02 < y < 0.7

D0

D* à π D0

  ZEUS, Q2 ≥ 1.5 GeV2   Luminosity 80 /pb

  EIC Luminosity 10-100 /fb/yr (1033 – 1034 /cm2/s)


EIC Kinematic Distributions

  Yu. Furletova

  Charm and Beauty events are different from inclusive DIS!


3

Minimum bias (e/p 10/100)

N~σL ~ 20·10-30·1034 ~200,000/secScattered e π±/K± e± μ± gammas from π0

PhP0.001<Q2<1

DIS1<Q2<100

DISQ2>100

σ~20μb

σ~600nb

σ~2nb

~5/event~0.02/event ~0.001 /event ~4/event

η

Pto

t,G

eV

p e


4Yulia Furletova

Charm BGF gγ->QQ

Scattered e π±/K± e± μ±gammas from π0

0.001<Q2<1

1<Q2<100

Q2>100

σ ~60 nb (e/p 10/100) N~60·10-33·1034 ~600/sec

11/event 0.2/event 0.2/event 7/event

Boson Gluon Fusion (BGF)

Pto

t,G

eV

η


5Yulia Furletova

Beauty BGF gγ->QQ

Scattered e π±/K± e± μ±gammas from π0

0.001<Q2<1

1<Q2<100

Q2>100

σ ~0.3 nb(e/p 10/100)

N~0.3·10-33·1034~3/sec

16/event 0.5/event 0.4/event 10/event

B¯ -> D0 µ ν, D0 -> K-π+

Pto

t,G

eV

η


EIC Charm Reconstruction

  S. Furletov   HVQDIS + PYTHIA


27 Jan. 2016 Sergey Furletov 3

Pt distribution & cuts

c à D*+ à π+slow

+D0 à π+ K–

pT (D*+)

pT(π+slow

)

pT(K–) pT(π+D0)


Secondary Vertex (D0àπK)

  S. Furletov Pythia simulation

  EIC Kinematics 10 x 100 GeV2

27 Jan. 2016 Sergey Furletov 6

Vertex distribution


LDRD Next Steps   Kinematic Distributions

& Reconstruction Efficiencies differential in xglue

  Which performance characteristics (and which portions of detector) are crucial to charm and beauty reconstruction

  Vertex Tracker   Design and performance

(Yu. Furletova)

Kinematics of charm production

0

0.5

1

1.5

2

2.5

3

3.5

4

-1.2 -1 -0.8 -0.6 -0.4 -0.2 0log10(xBJ)

log 10

(Q2 )

S. Furletov 12 Feb 2016 10x100 GeV2


EIC @ JLab Vertex Tracker   Initial concept, implementation

in GEMC and event simulation   Yu. Furletova, 10 Feb 2016

  Central beam pipe concept  C.H., Z. ZhaoàGEMC 12 Feb 2016

3 m

Central- Solenoid, Detectors, not shown

Forward-ion Dipole

Forward iFFQ

Upstream eFFQ + Shield


Conclusions   Exciting program to probe gluon structure on nuclei

  Important driver for EIC Detector design

  80 m long detector:   From 0° electron tagger

& Compton Polarimeter to ion far-forward spectrometer & neutron ZDC

Forward Dipole 6 mrad bend (Pbeam)

Ion FFQ Far-Forward

Dipole

ZDC

High-Dispersion Focus

Tracking Volume

16 m long


nuclear gluons with charm at eic* · 2016. 2. 17. · open charm production charles hyde old...

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